WO1982003747A1

WO1982003747A1 - Systemic pesticide product and processes for making and using it

Info

Publication number: WO1982003747A1
Application number: PCT/US1982/000553
Authority: WO
Inventors: Spike Inc Int; Michael J Cousin; William T Lawhon; Richard G Sinclair; Barney W Cornaby
Original assignee: Int Spike
Priority date: 1981-04-29
Filing date: 1982-04-28
Publication date: 1982-11-11
Also published as: IT8248304A0; BR8207666A; EP0077399A1; EP0077399A4; ES511782A0; GR75995B; ES8305559A1; OA07290A; JPS58500613A; MA19462A1; NO824358L; PT74824A

Abstract

Biodegradable products release, when inserted into the soil systemic pesticides at a controlled rate over a prolonged period of time. The biodegradable compositions can be formed into spikes that can be driven into the soil without sustaining damages. The products comprise a solid, hydrophilic water-soluble polymeric binder and a systemic pesticide. Optional ingredients include plasticizers, fillers, colorants and a coating. The products are made by mixing the dry ingredients and shaping the resulting mixture by melt extrusion injection molding or another suitable method to form suitable shapes such as spikes. In the alternative, the resulting mixture is injection-molded to form products having desired shapes. The formed products can then be coated with a water permeable coating. The products are inserted or driven into the soil in the vicinity of the plant. The moisture of the soil penetrates the biodegradable coating (if any) the matrix and begins to dissolve the matrix and the pesticide contained therein. The pesticide is initially rapidly released then it is released in a controlled manner for a prolonged period of time. The released pesticide is absorbed by the roots of the plant into the sap making it poisonous to pests. The initial rapid rate of release results in quickly killing at least a major portion of the pests on the plants in the vicinity of the product and the subsequent controlled release kills the remaining pests and prevents the reinfestation of the plants.

Description

SYSTEMIC PESTICIDE PRODUCT AND PROCESSES FOR MAKING AND USING IT

BACKGROUND OF THE INVENTION

This invention relates to pesticide-releasing compositions. In particular, it relates to compositions which gradually and controllably release a systemic pesticide into the soil.

Farmers and plant growers have always had to face a problem of partial or total loss of their crops or plants to pests. Over the years a number of pesticidal compositions (pesticides) have been developed to eliminate the predators (pests) from the crops or plants.

As used herein the term "pesticides" includes insecticides, fungicides, herbicides, miticides, nematocides and bactericides.

Various approaches have been devised to supply the pesticide to the plants. One common approach is to spray or otherwise deposit the pesticide on the surfaces of the plants. A number of patents disclose various pesticides and methods of applying the same directly onto the surfaces of the plants. See e.g., U.S. Patent No. 3,992,227 (Bradburne) and U.S. patent No. 4,102,991 (Kydonieus). This approach, however, has a number of drawbacks. First, the task of depositing of pesticide on individual plants is expensive and time consuming. Second, since the pesticides are generally poisonous, the task of applying the pesticides onto the plants involves a health hazard to the operator. Finally, the pesticides thinly spread on the surface of the plants are exposed to the atmosphere and quickly lose their pesticidal properties. The pesticide is often washed off or otherwise removed from the surface of the plant by rain or wind. This necessitates frequent reapplications of the pesticides. Another approach is to apply the pesticide to the soil in the vicinity of a plant in order to destroy pests on the roots of the plant. For example, U.S. Patent No. 1,038,316 (Dokkenwadel) discloses this approach. This approach suffers from several disadvantages. Specifically, such pesticides do not protect the above-the-ground part of the plant against pests. Additionally, such pesticides tend to be dissolved shortly after they introduced into the soil. Accordingly, it is extremely difficult to maintain the concentration of pesticides at high enough levels to continuously destroy the pests, without poisoning the entire area.

In order to increase the useful life of the pesticides a number of slow release products have been proposed. For example, U.S. Patent No. 4,007,258 (Cohen et al) discloses a sustained release pesticidal product which includes a pesticide, a biological binding agent in a matrix of water-insoluble but water swellable hydrophyllic polymer. The biological binding agent binds the pesticide and prevents its immediate release but allows for its gradual release. The problem with this approach is that an appropriate biological binding agent has to be found for a given pesticide. This can be a formidable task and in some cases an impossible one.

U.S. Patent No. 3,074,845 (Geary) discloses a controlled release pesticide product which is made by encapsulating, impregnating or coating the pesticide with an ami do- aldehyde type resin . Canadian patent No . 846 , 785 (Allen) reports a number of problems inherent in the products made in accordance with the invention described in the Geary patent. Specifically, the amido- aldehyde resins must be decomposed by microorganisms in the soil in order to effect the release of the pesticide. Accordingly, the release rate is slow and not uniform because it depends on the type of microorganism present in the particular location. The amido-aldehyde resins are also incompatible with many desirable pesticides and the polymerization reaction reportedly destroys some of the potentially useful pesticides.

U.S. Patent No. 3,269,900 (Rubin) discloses a slow release pesticide product made by enclosing a pesticide in a polyurethane foam. The foam is decomposed by microorganism to release the pesticide. The release of the pesticide from the product disclosed in the Rubin patent is therefore dependent on the particular soil and microorganisms present therein.

U.S. Patent No. 3,248,288 (Wilder et. al.) discloses a pesticide product made by admixing a hydrocarbon solution of a pest control material with a polymeric material and cooling the resulting mixture to form said product. The liquid carbon volatilizes carrying the pesticide with it. The Allen patent reports that this approach is unsatisfactory for general applications because hydrocarbons are generally toxic. Therefore, the evaporation of the volatile components present safety problems in producing the product, transporting, storing and using it. Some of the problems associated with applications of pesticides onto the surface of the plant or into the soil have been alleviated by the use of systemic pesticides. A systemic pesticide is introduced to the soil surrounding a plant. The plant absorbs the pesticide through its root system into the sap and carries it with the sap to the leaves. Insects and other pests that come in contact with or feed on the leaves absorb the pesticide from the sap either by ingesting the sap or absorbing it through their exteriors. Thus, systemic pesticides can be applied into the ground rather than on each and every surface of the plant. They generally remain active for a longer period of time than the pesticides applied directly onto the surface of plants. Finally, since the pesticides are in the sap of the plants, the plant is protected from pests that attack the roots as well as those that attack leaves and stem of the plant. See e.g. U.K. patent No. 679,631 (Ripper). Despite numerous advantages of systemic pesticides their acceptance has not been overwhelming because of a number of serious problems. Probably one of the most serious problems is that the systemic pesticides quickly dissolve in the soil and shortly after their introduction most of the pesticide is available to the plant. The plants, however, can only absorb a limited amount of the pesticide. The remaining portion is washed away and is not later available for absorption by the plant's roots. Since the majority of the systemic pesticide is washed away before it is utilized by the plant, the use of systemic pesticides is extremely expensive. If large access of a systemic pesticide is introduced in the vicinity of the plant, the pesticide can effect phytotoxity to the plant thereby causing partial or total destruction of the plant. In order to maintain adequate levels of pesticides in the sap of the plants, the systemic pesticides must be frequently resupplied into the soil. The repeated applications of the systemic pesticides increases labor expenses. In addition, the accumulation of certain pesticides in the soil can cause health hazards.

Another problem stems from the fact that systemic pesticides are generally harmful to humans. This makes the handling and application of systemic pesticides into the soil hazardous to operators' health.

One attempt to eliminate the above-mentioned problems is described in U. S. Patents Nos. 2,759,300 and 2,809,469 (Hartley patents). The Hartley patents disclose a device comprising a shaft and a head of solid material attached to one end of said shaft. The material includes systemic insecticide covered with a water-soluble coating. If a liquid pesticide is used, the material can also include an inert carrier such as plaster of paris. The shaft is pushed into the soil until the head is beneath the surface. The moisture in the ground gradually dissolves the coating, exposing the insecticide material. The insecticide material then permeates into the soil and is absorbed into the ground. The Hartley patents' attempted solution of the above-mentioned problems has not been entirely successful because the coating merely delays the introduction of the insecticide into the soil. Once the coating is dissolved the entire insecticide material is immediately made available to the plant. Accordingly, the disadvantages associated with excess insecticides being available to the plant are not eliminated by the device disclosed in the Hartley patent. Additionally, the Hartley device includes a nonbiodegradeable metal shaft which litters the ground each time an insecticide is introduced. The Allen patent discloses controlled release pesticide products which include a pesticide in a thermoplastic polymeric material. Some of the pesticides disclosed in the Allen patent are systemic pesticide. The thermoplastic material is hydrophobic; acordingly, the pesticide is released from the polymeric matrix by the process of molecular diffusing of its molecules through the molecular lattice of the polymer. The problem with this approach is that the release is quite slow and the infected plants can be severly damaged or even destroyed by the pests before the pesticide begins to kill the pests. The problem of delayed action of the pesticide is especially severe when the pesticide is used on small delicate plants, such as common household plants. Since such plants are small, the pests can multiply and inflict damage to the plant before the pesticide has any significant effect on the pest population. Another problem associated with the products disclosed in the Allen patent is that the product uses expensive binders. The total cost of the product make it uneconomical for sales to consumers.

There is, therefore, a long felt and unsatisfied need for a systemic pesticide product which does not suffer from the above-mentioned disadvantages.

One object of the present invention is to recognize the problems inherent in the prior art and to provide a solution to said problems.

Another object of the present invention is to define a class of compounds and a method of selecting and combining said compounds to produce a systemic pesticide product that does not suffer from the disadvantages of the prior art products.

A further object of the present invention is to form a product which rapidly begins to release the pesticide and continues to gradually release it for a prolonged period of time.

A still further object of the present invention is to provide a systemic pesticide product which has the structural strength and integrity to maintain its shape and which is shaped to facilitate its insertion into the soil and to provide an efficient safe method of inserting the product into the soil. Still another object of the present invention is to provide a systemic controlled-release pesticidal product that can be made without health hazards, efficiently kills a wide variety of pests for a prolonged time period, can be safely handled by humans and can be easily inserted into the soil.

A still further object of the present invention is to provide a controlled-release systemic insecticide product which quickly kills pests commonly found on household plants substantially without damaging said plants, which once applied continues to kill such pests for a prolonged time and which prevents infestation of healthy plants by pests.

Other objects of the present invention will become apparent to those skilled in the art upon studying this disclosure.

SUMMARY OF THE INVENTION

The present invention provides inexpensive products which when inserted into the soil in the vicinity of a plant's roots quickly release a sufficient dosage of a systemic pesticide into the soil to rapidly kill pests on the plant and/or to rapidly prevent infestation of a plant, and thereafter releases the pesticide at a controlled rate over a prolonged period of time.

The products of the present invention comprise a matrix of a water-soluble, hydrophilic, polymeric binder and a systemic pesticide dispersed within said matrix. Upon insertion of the product into the soil in the vicinity of a plant's roots, the moisture in the soil penetrates the hydrophilic matrix. The matrix begins to disolve and concurrently the systemic pesticide is disolved in the soil water and transported into the plant's roots. It is then disolved in the sap and transported with the sap throughout the plant. This release mechanism allows for a rapid supply of the pesticide to the plant so that pests can be eliminated before they inflict serious damage to kill the plant. Thereafter, the matrix continues to be eroded by the moisture of the soil providing continued gradual supply of the systemic pesticide to the plant so as to kill the remaining pests and/or prevent reinfestation.

The products of the present invention generally comprise from about 25 to about 99 and preferably about 25 to about 95 weight per cent of the binder and 1 to 75 and preferably 5 to 75 weight per cent of the systemic pesticide. Optional ingredients include plasticizers, fillers, colorants and a coating. The use of fillers produces a product which is less expensive. The coating makes the product safe to handle and provides an additional control over the release rate of the pesticide.

The present invention also provides processes for making the products without creating health hazards. The ingredients are mixed. The resulting mixture is subjected to sufficiently high temperature and/or pressure so as to form a continuous rod. The rod is then cut into suitable shapes, such as spikes. The preferred way of forming the rod is by melt extrusion. In the alternative, the resulting mixture is injectionmolded or otherwise shaped to form products having desired shapes. The products can then be coated with a preferably biodegradable coating.

Additionally the present invention provides a method for using the products without creating health hazzard. In accordance with one aspect of the present invention, the products are formed into spikes that can be driven into the soil without sustaining damage. Once the products are inserted or driven into the soil in the vicinity of the plant, the moisture of the soil penetrates the coating (if any) and disolves the polymeric matrix and the pesticide released as the result of the disolving of the matrix. The pesticide is transported by the soil moisture to and absorbed by the roots of the plant into the sap making it poisonous to pests.

The preferred systemic pesticide product of the present invention comprises DimethyIphosphate of 3-hydroxy-N-methyl-cis-crotonoamide, O,O-dimethyl-O- (2-methylcarbamoyl-1-1-methylvinyl)-phosphate, or O,O-Dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate, or O,O-Dimethyl acetylphosphoroamidthioate or O,S-dimethylacetylphosphoroamidothioate. In a polymeric matrix of poly (ethylene oxide) or poly (ethylene glycol). The product when inserted into the soil in the vicinity of household plants is effective in rapidly killing pests normally found on household plants and preventing infestation of the plants for a prolonged time, substantially without damaging the plants.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a side-elevational view of one preferred embodiment of the insecticide spike of the present invention.

FIGURE 2 is a cross-sectional view of the spike of FIG. 1 taken along line 2-2 thereof. FIGURE 3 shows a flow chart of a first preferred method of manufacture of spikes of the present invention of manufacture. FIGURE 4 shows a diagram of a second preferred method of manufacture of spikes of the present invention.

FIGURE 5 shows a diagram of a presently preferred commercial method of manufacture of spikes of the present invention. FIGURE 6 is a side-elevational view of presently preferred commercial embodiment of the insecticide spike for household plants, made in accordance with the present invention.

FIGURE 7 is a cross-sectional view of the spike of FIG. 6 taken along line 7-7 thereof.

FIGURES 8-10 are diagrams depicting profiles of the release of the systemic pesticide as a function of time from products made in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a controlled-release systemic pesticide product which is safe to handle even by the general public. When inserted into the ground in the vicinity of a plant, the product of the present invention rapidly begins killing pests on the plant and continues to kill them for a prolonged period of time and/or prevents infestation of the plant by pests for a prolonged period of time, substantially without adverse effects on the plant. The product of the present invention is designed to release a sufficient dosage of systemic pesticide to kill pests on the nearby plants within a relatively short period of time or to prevent infestation of a healthy plant and then continue to supply the pesticide to the plant gradu ally at a controlled rate for a prolonged period of time.

The composition products of the present invention include a systemic pesticide and a hydrophilic, water-soluble binder. The binder forms a matrix which confines the pesticide and which prevents a sudden release of the pesticide into the soil. The relative amounts of the pesticide and the binder vary depending on the desired characteristics of the product and the specific binder and pesticide used. The amount of the binder in the product must be sufficient to hold the pesticide and to prevent its immediate release into the soil and to maintain the shape of the product. The binder generally comprises from about 25 to about 99 and preferably about 25 to about 95 weight percent of the product. The systemic pesticide comprises from about 75 to about 1 and preferably from about 75 to 5 weight percent of the product. The most preferred product includes from about 30 to about 70 weight percent of binder and from about 70 to about 30 weight percent of pesticide.

The additional ingredients that can be included in the composition include 0 to 5 weight percent of plasticizer, 0 to 70 weight percent of a filler, 0 to 2 weight percent of a colorant and 0 to 20 weight percent of a protective coating which is preferably water permeable. The preferred amounts of plasticizers, fillers, colorants and protective coatings are 2, 43, 2 and 7 weight percent of the product.

It has been discovered that the addition of fillers to the composition to replace the binder results not only in savings due to lower costs of binders but also produces a product which is stronger and more durable. It has also been discovered that the protective coating of the present invention not only makes the product safe to handle by the consumer but also can be used for additional control of the release rate of the pesticide from the product. It is preferred that all ingredients of the product of the present invention be biodegradable or be normal soil components. Accordingly, the preferred product of the present invention does not litter the soil.

The systemic pesticide product of the present invention includes a systemic pesticide in a matrix of a polymeric binder. It has been discovered that systemic pesticides and binders must satisfy a number of specific criteria in order to be useful in the product of the present invention. Specifically, the systemic pesticide must:

(1) be stable at the fabrication temperatures of the product; (2) have sufficient solubility in water to be readily disolved and transported to and in the sap of the plant;

(3) remain stable and active within the normal pH range found in both soils and plants; and,

(4) have ability to kill the desired pests. Preferably the systemic pesticides used in the product of the present invention should:

(1) have a vapor pressure at ambient temperatures sufficiently low to substantially avoid the production of toxic vapors;

(2) have half-life of that permits a prolonged release thereof from the product; (3) not decrease the physical strength and integrity of the binder at desired concentration so as to make the product break and/or crumble upon insertion into the soil;

(4) have melting point above the maximum fabrication temperature;

(5) have LD₅₀ low enough to be useful; and,

(6) have minimal effect on mammals, bees, wildlife, humans.

If the products are molded by extrusion the fabrication temperatures of the products of the present invention are generally 50°C. Accordingly, the systemic pesticide should preferably be stable at least above and have its melting point below about 50°C. The preferred systemic pesticide that satisfy the vapor pressure requirement are those that have vapor pressures below about 10 mm Hg at room temperature (about 20°C). The preferred systemic pesticides have water solubility in the range from about 1.0 to 100 g of pesticide per

100 ml of water. The systemic particles of the present invention are stable at pH range of about 4 to 9, the common range of soil and plant pH. The preferred half life is in the range from about 15 to 30 days. To satisfy the sixth requirement, the systemic pesticide should preferably be solid at τemperatures at which it is applied to plant (generally 10-40°C). The preferred systemic pesticides exhibit toxicity with respect to a wide range of pests and especially good toxicity with respect to aphids, cyclamen mites, fungus gnats, leaf miners, mealy bugs, millipedes, red spider mites, scales, thrips, two-spotted spider mites, and whiteflies. The most preferred are those systemic pesticides that effectively kill aphids, spider mites and mealy bugs. The LD₅₀ of the systemic pesticides should preferably be in the range from about 20 to 100. The oral LD₅₀ should preferably be less than 500 mg/kg. The binder must be water soluble at rates that permit a prompt release of the systemic pesticide upon initial contact with the moisture in the soil and a sustained controlled release of the systemic pesticide thereafter. In order to accomplish a rapid initial release of the systemic pesticide from the product, the binder should be hydrophilic and water soluble. A.ddi.tionally the binder should: (1) inflict no phytotoxic effects on plants;

(2) be capable of being intimately mixed with the systemic pesticide without the pesticide becoming fugitive;

(3) not react with the pesticide in the manner that destroys the function of each in the product;

(4) have softening temperature below the decomposition temperature of the systemic pesticide; and (5) impart a sufficient strength to the fabricated product to maintain it substantially intact during packaging, storage, shipment and insertion in the soil. Upon forming, the binder should preferably be non-toxic to humans.

The present invention offers numerous advantages. First, the product rapidly releases a sufficient dose of the systemic pesticide shortly after being inserted into the soil to kill pests and then continues to release the systemic pesticide at a controlled rate to eliminate the remaining pests (if any) and to prevent infestation or reinfestation. Since the composition of the present invention releases the systemic pesticide in a gradual and controlled manner, the pesticide is efficiently utilized and lasts for a prolonged period of time. The pesticide is supplied to the plant gradually at rates that do not harm the plant. Additionally, the gradual and controlled utilization of the systemic pesticide prevents accumulation of unused pesticides in the soil. Since the pesticide is efficiently utilized, it lasts for a prolonged period of time thereby saving the product and the work required for keeping the pesticide levels of the soil in the vicinity of plants sufficiently high to prevent pests. Another advantage of the composition of the present invention is that it can be formed into spikes that can be driven into the soil without breaking or shattering. The composition is rugged enough to maintain its integrity during packaging, transportation and in storage, and it is stable under normal atmospheric conditions so that it can be stored for prolonged periods of time. If coating is applied to the surface of the composition of the present invention, the resulting composition can be handled even by consumers during storage, transportation and planting into the soil without the danger of poisoning.

It should be noted that the spikes made in accordance with the preferred embodiment of the present invention are safe for consumer handling not only because of the protective coating and the use of a polymer matrix to shield the pesticide but also because during normal use they emit practically no toxic fumes and have low dermal and inhalation human toxicity.

Further advantages of the preferred products of the present invention are that they are biodegradable and that they are self contained, i.e., they include a predetermined amount of a systemic pesticide and require no measuring, mixing or other handling by the user of the product. Other advantages will become apparent to those skilled in the art upon studying this disclosure. The ingredients used in the products of the present invention will now be separately described.

Pesticides The systemic pesticides include water-soluble thiocarbamates, phosphocarbamates and thiophosphocarbamates that satisfy the criteria set forth above.

One presently preferred systemic pesticide is O, S-dimethylacetylphosphoroamidothioate which is made by Union Carbide Co. under the name Standak. Another preferred systemic pesticide is O,S-dimethylacetylphosphoramidothioate, commonly known as acephate. It is available as a wettable powder under the trade name Orthene, from Chevron Chemical Company, San Francisco, California. Less effective than the two preferred pesticides but still acceptable systemic pesticide is O,O-dimethyl- O-(2-methylcarbamoyl-1-methylvinyl)phosphate, commonly known as monocrotophos and sold as "Azodrin" and O,O-dimethyl-S- (N-methylcarbamoylmethyl)-phosphorodithioate, commonly known as dimethoate, and sold under various trade names including "Cygon".

Binders

Generally, the binders suitable for use in the products of the present invention are those that satisfy the general criteria set forth above. Two types of polymers have been found to be superior in the fabrication of the product of the present invention and were found to produce spikes which meet the objectives of the present invention and are drivable into the soil without breaking or shattering. The first type is polyethylene oxide)s, the second is poly(ethylene glycol)s. Poly(ethylene oxide)s are preferred because they allow the fabrication of the pesticide composition of the present invention by either melt extrusion or by injec tion molding. When poly(ethylene glycol)s are used as the binder, the product cannot be fabricated by melt extrusion. The reason for it is that melted poly(ethylene glycol)s do not provide sufficient green strength to allow for the formation of a uniform rod of material that can then be cut into desired shapes.

The presently preferred binders are solid poly(ethylene oxide)s having molecular weight in the range from about 100,000 to about 900,000. Especially preferred is poly(ethylene oxide) having an average molecular weight of about 100,000 and a narrow molecular weight distribution. Such binder is presently commercially available under the trade name "Polyox WSR N-10" from Union Carbide Corporation, New York, New York.

Other poly(ethylene oxide) binders available from Union Carbide include: "Polyox WSR N-80", "Polyox WSR N-750", "Polyox WSR 205" and "Polyox WSR 1105", having average molecular weights of 200,000; 300,000; 600,000 and 900,000, respectively.

Examples of poly(ethylene glycol)s that can be used in connection with this invention include "Carbowax 4000", "Carbowax 6000" and "Carbowax 14000", sold by Union Carbide Corporation, New York, New York.

Fillers

Fillers can be used in the pesticide products of the present invention to reduce the cost of the products. Fillers are significantly less expensive than binders; therefore replacing some of a binder with a filler reduces the overall cost. Examples of fillers suitable for use with the composition of the present invention include clay and corn cob. Clay is especially preferred because, surprisingly, it has been found to improve the hot melt strength and the viscosity of the molten composition during fabrication. As a result, during processing a hot extruding rod can be subj ected to tensile stresses without breaking. An example of useful clay is Spray Satin Clay commercially available from Englehard Minerals and Chemicals Corporation, Iselin, New Jersey. Corn cob can be purchased from The Andersons in Maumee, Ohio.

Plasticizers

Plasticizers are used as a fabrication aid. They lower the viscosity of the composition at melt stage. The presently preferred plasticizers include poly(ethylene glycol)s having an average molecular weight from about 400 to about 6000. Especially preferred is polyethylene glycol having an average molecular weight of 4000. This poly(ethylene glycol) is commercially available under the trade name designation "PEG 4000" from Union Carbide, New York, New York.

Colorants

A colorant may be added to improve the product's appearance. Examples of colarants include: brown iron oxide sold as "Brown M Oxide" by Hercules, Inc., Wilmington, Delaware; carbon black, sold as "Raven 5250" by Cities Service Co., Atlanta, Georgia; corn cob, sold by The Andersons, Maumee, Ohio; ferric ammonium, sold as "Melori Blue" from American Cyana-id, Bound Brook, New Jersey; a mixture of zinc and cobalt oxides, sold as "Green V-11655," by Ferro Colors, Cleveland, Ohio; red iron oxide, sold as "iron Oxide" by Pfizer, Inc., New York, New York; clay, sold as "Spray Satin Clay" by Englehard Minerals & Chemicals, Iselin, New Jersey; and titanium dioxide, sold as "Unitane" by American Cyanamid, Wayne, New Jersey. Other colorants will be apparent to those skilled in the art. Brown iron oxide is presently preferred because it has been found particularly acceptable to consumers.

Coatings A coating applied on the surface of the product serves several functions. First, it protects the user of the product from accidentally absorbing some of the insecticide through the skin. Second, it enhances the stability of the product because it prevents the spike from absorbing moisture from the air during routine handling. Suitable coatings include biodegradable polymers, such as cellulose acetate, alkyd resins, alkydacrylic copolymers, and poly(vinyl acetate)s. The use of a biodegradable coating which is water-soluble provides an important additional advantage. Namely, it significantly slows down the rate at which systemic pesticide is released into the soil. An example of a water insoluble biodegradable coating is cellulose acetate. The coatings are generally applied in a liquid form and then dried on the surface to form a solid coating. Solvents such as ethyl acetate can be used to form a solution for coating the product. Other solvents will be apparent to those skilled in the art. The presently preferred coating is a 10 percent solution of cellulose acetate dissolved in ethyl acetate. The preferred cellulose acetate is commercially available under the trade name "AC6555", from Eastman Chemical Products, Kingsport, Tennessee.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE PRODUCT

The invention will now be described in connection with the preferred embodiment of the product shown in the drawings. Referring now to the drawings, FIG. 1 depicts a systemic insecticide spike constructed in accordance with the present invention and designated generally by a numeral 10. The spike 10 includes a generally cylindrical trunk 12 and a tapered section 14 terminating at a tip 16. This shape of the spike facilitates its drivability into the soil. Depending on the size of the spike and the conditions of the soil, the spike can be manually pushed into the soil or it can be driven into the soil' by a hammer or other suitable means. A removable plastic or a metal cap (not shown) can be placed on the trunk at the end opposite from the tip 16 to prevent chipping if the spike is hammered into the soil.

As shown in FIG. 2 , the spike 10 includes a coating 19 and a composition 21. The composition 21 comprises a systemic insecticide, a binder, a plasticizer, a filler and a colorant. The general and preferred weight percentages of each of the ingredients and the preferred species of each ingredient are the same as those stated above for the pesticide compositions.

The presently preferred systemic pesticides are is O,S-dimethyIacetylphosphoramidothioate, commonly known as acephate and O,S-dimethylacetylphosphoroamidothioate. The former is available as a wettable powder under the trade name ORTHENE®, from Chevron Chemical

Company, San Francisco, California. The latter is made by Union Carbide under the name Standak. If ORTHENE® is used, preferably 20 percent by weight of the spike should be ORTHENE®, but the amount of ORTHENE® used may range from 1 percent to 75 percent by weight of the spike. The present most preferred range of insecticide is between 10 and 30 percent. PREFERRED PROCESSES OF MANUFACTURE The Extrusion Process

One preferred process for preparing the insecticide spikes will now be described with reference to FIG. 3. As shown in FIG. 3, the dry ingredients are first blended together using a conventional blender until a substantially uniform mixture is formed. The mixture is then fed into a hopper of a conventional screw type extruder. From the hopper the mixture is transported into the heated barrel of the extruder. As the mixture is conveyed by the action of the screws, it is simultaneously heated and compressed. The temperature of the barrel is generally maintained between about 65°C and 75°C. As the mixture is compressed and heated it forms a substantially homogeneous melt which is forced through a die at the end of the barrel opposite from the hopper. The die temperature is maintained in the range from about 70°C to about 80°C. The specific die size depends on the composition of the specific insecticide, the size of the extruder and the flow rate of the melt. The dies used in our experiments had diameters of 0.195 and 0.240. The dies were used in a single screw extruder having an L/D ratio of 20:1 manufactured by C.W. Brabender Instruments, Inc., South Hackensack, New Jersey.

The melted composition exits from the extruder in the form of a rod of material. The rod is cut into sections and can be shaped to form spikes having tubular sections tapering at one end to form a tip.

The product can be coated preferably with a biodegradable, water permeable but insoluble coating such as cellulose acetate. Such coating can be applied in any conventional manner, as by spraying or dipping the product into a solution of the coating material. The product is then either dried in the air or in an oven. It has been found that the coating is dried in an oven maintained at about 40°C in about 1 to 2 minutes.

The Injection Molding Process The second preferred process of fabricating the product of the present invention will be described with reference to FIG. 4. As shown in FIG. 4, the starting dry ingredients are blended together using a conventional blender until a substantially uniform mixture is formed. The mixture is then passed through a heating zone maintained at a sufficiently high temperature to melt it. The temperature is generally between about 80°C and 100°C and preferably between about 85°C and 95°C. The desired temperatures can be achieved, for example, in a heating chamber of Watson Stillman injection molder.

The molten mixture is forced under pressure to a mold. The resulting product is removed from the mold and cooled. Upon cooling the product solidifies. The solid product is then coated with a preferably biodegradable and water permeable but water insoluble coating of the type and in the manner described in connection with the extrusion process.

DESCRIPTION OF A PREFERRED COMMERCIAL PROCESS OF THE PRESENT INVENTION

The invention will now be further described in connection with a preferred commercial process of the present invention shown in FIG. 5. The process uses Orthene rather than Standak as the preferred systemic pesticide because ORTHENE® has already been cleared for use as a systemic insecticide in the United States.

Referring now to FIG. 5, the starting materials shown thereon and the source of these materials are as follows: Material Source

Polyox WSR N-80 Union Carbide Corp. PEO New York, New York

Carbowax 4000 ditto (Now 3550 ( PEG ) )

Clav Englehard Minerals Iselin, New Jersey

Ferro V 11655 Ferro Colors Green (Color) Cleveland, Ohio

Ferro F 6111 Brown Ferro Colors F 6112 Cleveland, Ohio

ORTHENEK Chevron Chemical San Francisco, CA

CA 1655 Eastman Chemical Cellulose Acetate Prod., Kingsport

Ethvl Acetate Eastman Chemical Prod., Kingsport, Tennessee

As shown in FIG. 5, polyethylene oxide, polyethylene glycol, clay and color are weighed or merered and then introduced into a mixer in preselected proportions. The materials can be transported into the mixer and throughout the process by screw conveyors, pneumatic carriers or portable bins.

The materials introduced into the mixer are thoroughly mixed preferably using an intensive mixer that assures break up of lumps and agglomerates and then is fed from the mixer into an extruder. Twin screw extruders, available, for example, from Cincinnati Milacron or Krauss Maffei, are presently preferred.

The rejects from the ex-ruder are ground in a grinder and recycled to the mixer. The acceptable extruded products are coated with a mix of ethyl acetate/ cellulose acetate solution mixed in a blender and introduced from a holding tank. The coating is applied onto the extruded product by dipping the product into the mixture. The coated product is then dried and cut, and the coating is then applied onto the cut ends of the product by dipping and the coating is dried. The rejects are returned to the grinder and after grinding recycled to the mixer. The solvent is recovered from coating and drying stages stored for further use in a storage tank. The commercially preferred spike 30 for household plants is shown in FIGURES 6-7 and it includes a composition 30 and a coating 37.

METHOD FOR USING PRODUCTS OF THE PRESENT INVENTION

The method of using the products of the present invention will now be described in connection with spikes shown in FIGS. 1-2 and 6-7.

The spikes are packaged and distributed to plant growers. Since the spikes do not readily decompose and do not break or shatter, they can be stored and transported without sustaining structural damages. Since they have a protective coating and are made with nonvolatile systemic pesticides and non-toxic binders, they can be handled safely during packaging, storing and distribution. The plant grower inserts or the spike into the soil near the roots of the plant to protect against insects or to kill insects on an infected plant. Depending on the size of the spike and the condition of the soil, the spike can be either pushed or hammered into the ground. The composition of the spikes of the present invention has a sufficient strength to avoid breaking or shattering while it is hammered into the soil.

The plant grower can handle the spike without fear of poisoning because the systemic pesticide is partially enclosed in the matrix formed by the binder and the matrix in turn is covered by a coating composition 21 that does not allow the user to come in contact with the active ingredient.

Once the spike is in the soil, the moisture from the soil penetrates the coating and begins to erode the matrix releasing the systemic pesticide. As the pesticide is gradually released into the soil, it is absorbed by the roots into the sap of the plant. The pesticide makes the sap of the plant poisonous to insect thereby kills the insects which attempt to feed on the plant and protecting the plant from infestation.

The binder, coating and optional ingredients that are not normally a part of the soil of the preferred embodiments are biodegradable; accordingly, they decompose so that there is no debris left in the soil as the result of the application of insecticide spikes of the present invention.

* * *

The following examples are provided to further describe the invention. These are provided for illustrative purposes only and are nor intended to limit the invention in any manner.

EXAMPLE NO. 1

The purpose of this experiment was to determine the effectiveness of six selected systemic insecticides in killing insects within 24 hours of the introduction of the pesticide product into the potted plant soil.

(A) Selection of Plant and Insect Species

Coleus was chosen as the plant in this experiment because it is a typical house plant and it is easy to grow in both natural or fluorescent lighting. Mealybugs were selected as the pest species because they are a common pest of coleus and because they can be seen and counted with the naked eye.

Several hundred healthy coleus plants were purchased from a nursery (Boulevard Gardens) in Columbus, Ohio. Approximately 100 coleus, heavily infested with mealybugs, were obtained from a second source, Ohio State University. Plants were 15 to 20 cm high. Each was transplanted to a four-inch pot containing commercial potting soil (3acto potting medium). Part of the unifested plants were placed in contact with the infested plants in a growth chamber. After about ten days, insect populations had dispersed to the new host plants. Plants infested with, mealybugs were maintained in growth chambers under the following conditions: temperature = 27° C; light intensity = 2,000 ft. candles (mixture of cool white and fluorescent bulbs); day length = 12 hrs. Plants were watered daily by subirrigation with distilled water and once weekly with one-quarter strength Hoagland's solution. Infested plants were maintained in a chamber separate from healthy control plants.

(B) Selection of Systemic Insecticides About 60 systemic insecticides were identified and screened for potential use in a plant spike during the early design phase. The following six systemic insecticides were selected as best candidates:

DesignaTrade Name tion Chemical Name Of The Sample

A Dimethylphosphate of 3-hydroxy- Azodrin N-methyl-cis-crotonamide or O,O- dimethyl-O-(2-methylcarbomoyl-1 methyl vinyl)-phosphate (monocrotophos)

B O,O-Dimethyl-S-(N-methylcarbamoylDimethoate methyl) phosphorodithioate DesignaTrade Name tion Chemical Name Of The Sample

C O,O-Diethyl-S-(2-(ethylthio)ethyl) Disuifctcn phosphorodithioate

D O,S-Dimethyl acetylphosphoroamidiOrthene thioate

E 5,6-DimethyI-S-(N-isopropylcarbaPrimor moyl methyl) phosphorodithioate F O,S-DimethylacetylphosphoroamidoStandak thioate

Criteria used in selecting the "best" insecticides included (1) high toxicity to insects, (2) low toxicity to humans, (3) usability on ornamental plants, (4) availability in the U.S.A., and (5) numerous chemical and physical properties.

(C) Experimental Design

The following experimental design was used for the study: (a) Six systemic insecticides;

(b) Three dosage levels of each insecticide;

(c) Three replicates of each condition; and

(d) Two conditions of plants: with insects and without insects. The study used 108 plants. plus 10 control plants. The control plants were infested with mealybugs but not treated with the insecticide.

Three dosage levels were used: low, medium, and high concentrations of each of the six insecticides. Dosages were determined on the basis of several factors. First, the percentage of active ingredients listed on the insecticide's label was noted. Next, the range of concentrations of the systemic insecticide in two 1000 mg spikes (assuming two will be recommended for a 4-inch ot) were determined as being between 0 percent to about 80 percent.

As an approximation of low, medium, and high concentrations it was decided to assume 10, 30 and 60 weight percent of the systemic insecticide. This meant that 200, 600, and 1200 mg of the systemic insecticide was needed, respectively. Because none of the systemic insecticide samples contained 100 percent active ingredient it was necessary to weigh out sufficient combined active and inactive ingredients to assure 200 mg of active ingredient. Table 1 lists these weights for the 10, 30 and 60 weight percent concentrations.

TABLE 1. DOSAGES (MILLIGRAMS INSECTICIDE APPLIED) FOR BIOLOGICAL EVALUATION OF SIX INSECTICIDES

Dosaσe

Low Medium Hiσh

10% 30% 60%

Insecticide (Al) (200 mg Al ) (600 mg Al) (1200 mg AI)

A 77.5 258 774 1,548

B 23.4 855 2,564 5,128

C 1 20,000 60,000 120,000

D 15.6 1,282 3,864 7,692

E 50 400 1,200 2,400

F 75 267 800 600

Prior to introduction of the insecticides, each pot was placed in a separate glass petri dish (6-inch diameter), and then spaced enough apart so there was no contact between plants. Insecticides were then distributed as evenly as possible on the top of the soil in each pot and then worked into the soil with a glass rod. Fifty ml. of distilled water was added to the tops of the pots to wash the insecticide into the soil. Any leached liquids and insecticide was retained in the petri dish. The highest dosage of substance C (120 g) proved to be too much to mix into the soil; therefore, this treatment was not performed.

All data collection consisted of visual observations. Prior to treatment the number of large mealybugs was counted to obtain a baseline to which counts from subsequent days could be compared. In the phytotoxic test, initial observations were qualitative color changes, leaf loss, or leaf death. The observations were recorded by means of code numbers identified in Table 2.

Observations were taken on the day of treatment with insecticides (day 0), and 1, 2, 4, 7, and 11 days after treatment. Additional toxicity readings were taken 8, 10, and 14 days after treatment. All plants were photographed 7 and 14 days after treatment.

TABLE 2. DESCRIPTIONS OF PHYTOTOXICITY EFFECTS

Code Description

0 There was no effect.

1 There was some leaf loss and/or leaf edges were turning brown.

3 There were many leaves lest and/or many leaves were turning brown.

4 All leaves were lost and/or all leaves were dead.

5 The entire plant was dead.

(D) Results

(1) Effects of Insecticides on Mealybug Population

As shown in Table 3, four of the six systemic insecticides (A, B, D, and F) were effective in killing mealybugs. Insecticide C and E, on the other hand, had little effect on the mealybug population.

TABLE 3. CHANGES (PERCENT) IN MEALYBUG POPULATION DURING EXPERIMENT

Time After Application of Insecticides

Insecticide Dosage 24 hrs. 48 hrs. 96 hrs. 11 days

A low - 27 - 80 - 94 - 100 medium - 70 - 90 - 98 - 100 high - 76 - 87 - 97 - 100

B low - 83 - 83 - 92 - 100 medium - 88 - 91 - 97 - 100 high - 84 - 84 - 97 - 100

C low 0 - 3 - 37 + 30 medium + 22 + 22 - 7 - 41

D low - 82 - 79 - 91 - 100 medium - 84 - 92 - 98 - 100 high - 81 - 86 - 100 - 100

E low + 52 + 48 + 61 + 65 medium + 23 + 31 + 46 - 4 high + 72 + 45 + 91 + 123

F low - 67 - 75 - 42 - 10 medium - 57 - 86 - 67 - 100 high - 64 - 100 - 71 - 100

Control + 8 + 26 + 26 + 67

Insecticide A killed up to approximately 80 percent of the original mealybug population after 24 hours and up to approximately 100 percent after 96 hours (Table 3). With these four "best" insecticides, total kill was accomplished after 11 days of treatment. From

Table 3 it can be seen that, in general, there was little difference between low, medium, and high treatments.

For instance, looking at B, the low concentration killed

L / 83 percent of the mealybugs after 24 hours, the medium concentration killed 88 percent, and the high concentration killed 84 percent. Thus, presentation of results considers the three dosages as being about the same.

Insecticide A was effective in all three concentrations with a total kill occurring after 11 days. During the first 24 hours a difference did exist between concentrations, with approximately 25 percent, 70 percent, and 75 percent of the population being killed by the respective low, medium, and high dosages. However, after 96 hours all three concentrations appeared to be equal in effect, with low concentrations eradicating 94 percent of the original population and middle and high concentrations killing approximately 95 percent of the baseline population.

Insecticide B was equally effective in all three concentrations, killing about approximately 85-90 percent of the mealybug population within 24 hours. After 95 hours the low dosage resulted in a 92 percent drop in population, and the medium and high dosages killed 97 percent drop in population. Total kill occurred after 11 days.

Insecticide C exhibited an opposite effect to that exhibited by A, B, D, and F. In the low concentration dose group, the population had increased after 11 days by approximately 30 percent above the baseline population. After 24 hours there was no change, while after 48 and 96 hours there were small drops in the population, i.e., 3 percent (48 hours) and 37 percent

(96 hours). The small drop followed by a large increase in population was probably due to a combination of causes. For example, there was likely a small effect of the pesticide but the increase in population over time was greater, and the net result was a population increase in the size-classes of insects being counted. On the other hand, the medium-dose concentration of C was effective to sor.e extent in curbing mealybug population, killing about 40 percent of the baseline population after 11 days.

After 24 hours D was equally effective in all concentrations tested, with 82 percent (low), 84 percent (medium), and 81 percent (high) of the original population killed. However, a small difference in effects did appear after 96 hours, at which time the low dose had killed about 90 percent of the original populations, the medium dose 98 percent, and the high dose 100 percent.

Insecticide E, like C, showed no to little effect on population reduction of mealybugs. With the low, medium, and high concentrations the respective populations of mealybugs increased up to 123 percent above the baseline population count after 11 days. Plants treated with low and high dosages of E contained mealybug populations at 65 percent and 122 percent above their respective treatment day populations. The medium dosages resulted in a small 4 percent reduction of the original population count.

Insecticide F, though not initially as effective as A, B, and D, caused 100 percent kill after 11 days at all dosages. After 24 hours all three dosages appeared equally effective, killing approximately 55-65 percent of the population. A difference in the effectiveness of dosages began to appear after 48 hours, at which time 75, 86, and 100 percent of the original populations had been killed for the respective low-, medium-, and high-dosage groups.

(2) Effects of Insecticides on Plant Population (Phytotoxicity)

Phytotoxicity of the six insecticides was studied and rated on a scale from 0 (no effect) to 5 (total plant death) as described in Table 2. All six pesticides, when compared to controls, were phytotoxic to coleus plants. The phytotoxicity varied from the loss of a few leaves or browning of edges, as in the case treated by F, to death of the entire plant, as resulted from the use of either D or B. A, E, and C exhibited moderate to strong phytotoxicities. With only two exceptions, no phytotoxic effects were observed during the first 6 days after treatment; thus, phytotoxic effects were manifested 5 or more days after treatment.

Numerical phytotoxicity ratings are shown in Table 4. Substance A caused moderate to strong phytotoxicity. The degree of phytotoxicity appears to be a function of concentration as well as time. The first effects were observed 7 days after treatment, at which time the low, medium, and high dosages exhibited average ratings of 2, 3, and 3 respectively (Table 4). Thus, moderate to large leaf loss or change of leaf color occurred. At 14 days after treatment, the average ratings were 3, 4, and 4 respectively, meaning large to total leaf loss or change of leaf color. Also, one of the plants (receiving the high dosage) received a rating of 5, indicating that the plant was dead.

Insecticide B was highly phytotoxic in all concentrations, killing medium- and high-dosage plants 8 days after treatment and all plants except one (which had a rating of 4 and was dying) after 14 days. Insecticide B was the fastest acting pesticide, exhibiting its effects only 4 days after initial application of the pesticide. Even at the low concentration it caused moderate to large leaf loss (rating of 3), and large if not total leaf loss or leaf death in the medium to high concentrations (rating of 4). By day 8, all middle

and high-dosages plants were dead, and all plants (with the above exception), were dead at 2 weeks.

Insecticide C also was moderately phytotoxic to coleus. The first visible effects were not observed until one week after administration of the pesticide, at which time the low-dosage plants had lost several leaves (rating of 2) and others had brown edges. The medium-dosage plants had no visible adverse effects. However, two weeks after treatment, C caused large leaf loss in two of three plants in the medium-dosage plants and total leaf loss or leaf death (rating of 4) in all the low- and in one medium-dosage treated plant.

Substance D, like B, was highly phytotoxic in all concentrations and exhibited effects only four days after pesticide application. At this time the edges of the leaves of the low- and medium-dosage plants were turning brown, while the high-dosage plants were losing leaves. By day 8 all high-dosage plants were dead, and by day 10 all plants in all concentration groups were dead, with the exception of one (which had a rating of 4).

Insecticide E exhibited a small to moderate phytotoxic effect; the effects varied proportionally with time as well as with concentration. At day 7 the low-dosage plants exhibited either no effect or edges of leaves were turning brown. The medium-dosage plants exhibited a loss of several leaves in addition to color change in leaves still on the plants. The plants in the high-dosage range were losing many leaves. By day 14, all plants were still alive. The low-dosage plants still exhibited only small leaf loss or brown-edged leaves (rating of 1). The medium-dosage plants had lost several leaves (rating of 2) while the high-dosage plants had either lost many leaves or had a large number of dying leaves (rating of 3)). Substances E and F produced the fewest phytotoxic effects of all insecticides tested. The first effects were not observed until day 8 when there was a turning of color in a few leaves in all plants at all concentration doses. By day 14 there was a loss of several leaves in 1 of 3 plants in the low-dosage group and in all 3 plants of the medium-dosage group. In the high concentration range all plants had lost many leaves. The controls received ratings of 0 (no effect) consistently throughout the 14-day experiment.

(3) Comparison of Insect and Phytotoxicity Effects

All the pesticides killed mealybugs and all exhibited some phytotoxic effect on coleus. Substances B and D have the greatest effect on both insect and plant populations. Insecticide E had the smallest effect on mealybug populations while E and F had the least phytotoxic effects. Insecticide B had the greatest effect, killing up to 90 percent of the bug population after 24 hours, and it exhibited a moderate to high phytotoxicity effect (2 to 4 on the rating scale) by the fourth day after treatment. It was lethal to plants as soon as 8 days after treatment, with total kill of the mealybugs occurring between 4 and 7.

Insecticide D, like B, killed a large portion of the mealybug population, i.e., 80 to 85 percent in just 24 hours. Again, however, like B, it was lethal to coleus after 8 days in three of the high-dosage group and in one medium-dosage group. By day 11 all insects were dead, but so were the plants.

Insecticide C and E appeared to be similar in their limited effectiveness in killing insects, but C was slightly more phytotoxic, causing large if not total leaf loss after day 11. Substance E never caused more than the loss of one large leaf.

Substances F and A were similar in their insectkilling effectiveness, but differed in their phytotoxic effects. These two pesticides were moderate in their insect-killing ability after 24 hours. The medium and high dosages of A killed 70 to 75 percent of the bugs, while F killed 60 to 65 percent of the population in all concentrations. Neither pesticide exhibited any phytotoxic effect. Insecticide F appeared to be the superior of the two, because although both had killed all insects by day 7, A was more phytotoxic by day 11 (exhibiting a rating of 3 to 4 on the phytotoxicity scale).

(E) Conclusions

This experiment tested effects on mealybugs and coleus plants only.

Several of the six insecticides killed 60 to 80 percent of the mealybugs within 24 hours. And four insecticides killed 100 percent of the mealybugs within 11 days; B, D, A and F. Insecticide F is the best overall insecticide. It killed insects initially and its killing power was sustained. Substance F showed the least phytotoxic effect of all six insecticides were to some extent phytotoxic. By comparison, A, D and B killed (in the early part of the experiment) approximately equal numbers of mealybugs at all concentrations and the lower concentration are less phytotoxic than the medium and high dosages . This implies that even lower dosages would be less phytotoxic in effect but still maintain a toxicity for insects.

Thus, the experiment showed that insecticide F is the best. Insecticide A is second best, while D is the third choice. The fourth one is B. Neither C nor E killed mealybugs over the 11-day experiment.

EXAMPLE NO. 2 The purpose of this experiment was to determine the amount of ORTHENE® that needs to be incorporated into each systemic insecticide spike to kill within 24 hours over 50 percent of the mealybug population on small coleus plants without causing visible phytopathological reactions to the coleus plants.

(A) Procedure

The experimental design consisted of two runs. In the first run the design was: 1 species of plant (coleus) X 2 individual plants (4 for reference) X; 4 exposures (0, 2.5, 10, and 30 percent concentration of ORTHENE®; 4 sampling times (days 0, 1, 2 and 9). This represented a total of 40 measurements. At each measurement the number of mealybugs larger than the first instar was counted on each plant and pot environs and two or three leaves were removed from each plant for analysis of radioactive content.

In the second run the design was slightly modified to place more emphasis on the number of plants being exposed to a given dose of ORTHENE® in a spike. The second design was comprised of 1 species of plant (coleus) X 5 individual plants 4 for the reference X 3 exposures (0, 15, and 25 percent loading of a.i. per spike X 7 sampling times (days 0, 1, 2, 4, 8, 13 and 16). At each measurement time the number of mealybugs larger than the first instar was counted on each plant.

Healthy coleus were obtained from a nursery in Columbus, Ohio. Plants were in 4-inch pots and were about 6 inches tall. Plants were grown in a medium comprised of 33 percent vermiculite, 33 percent sand and 33 percent of peat. Coleus plants were housed in temperature-controlled greenhouse bays and given normal watering. Mealybugs were obtained from infested plants in nurseries and maintained on large nurse plants. When experiments were started we selected similar sized coleus plants with similar infestation levels of mealybugs. Spikes were made according to the procedures discussed in detail in Example 6. Briefly, ORTHENE® was melt blended in a polymer matrix. The blend was then poured into molds to form spikes which then were coated with a clear polymer. Spikes were placed in air tight jars and used in the above experiments within a few weeks after they had been made.

(B) Results

(1) First Run

The insecticide spikes were effective in reducing populations of mealybugs on small coleus plants. A population averaging 58 and ranging from 18 to 113 mealybugs per plant represented the initial populations (Table 4A). Within 24 hours as many as 80 percent of the mealybugs were killed or displaced from plants tested with the highest dosage (1 spike with 30 percent of active ORTHENE®).

Mealybug populations exposed to spikes containing 30 weight percent of active ORTHENE® dropped from an average of 80 individuals per plant to 40 individual (about 50 percent less) within 24 hours (Table 4B). By

48 hours the number of mealybugs averaged 14 individuals this was about 20 percent of the initial population. Response to 10 weight percent was less dramatic. Populations decreased by from an average of 52 to 35 (day 1) and from 35 to 30 (day 2). In terms of percentage this TABLE 4A. NUMBER OF MEALY BUGS ON SMALL COLEUS IN FIRST EXPERIMENT. THE SMALL COLEUS WERE INFESTED WITH MEALY BUGS AND EXPOSED TO VARIOUS DOSAGES IN ONE INSECTICIDE SPIKE

Dosage

0 2 10 30

Day of Name of Sampling Plant: A B C D X E F X G H X I J X

0 18 25 22 82 38 39 92 66 25 78 52 113 45 79 1 20 29 18 79 39 31 100 66 24 46 35 64 16 40

2 23 23 12 85 36 31 107 69 17 42 30 15 13 14

9 23 45 28 95 48 19 18 19 13 3 8 0 0 0

was a 33 percent drop (day 0 to day 1) and a 43 percent drop (day 0 to day 2). Finally, there was no decrease in numbers for spikes containing 2 weight percent ORTHENE®. As expected reference population tended to increase over the period of observation. For example, the average initial populations was 39 and by day 9 it was 48 individuals. Thus, the spikes containing 30 weight percent and 10 weight percent of ORTHENE® were the most effective.

(2) Second Run

In the second run dosages of 15 and 25 weight percent of active ORTHENE® were used. Mealybug populations declined on treated plants. Populations on plants dosed with 25 weight percent dropped from an average of 118 mealybugs per plant to 84 insects (day 1) and to 24 (day 8). This represented a 30 percent decrease in the number of insects within 24 hours and a 80 percent decrease within 8 days. The plants that received spikes containing 15 weight percent of active ORTHENE® also exhibited a decrease in the number of mealybugs. The initial average of 76 mealybugs per coleus plant (Table 4B) dropped to only 72 (day 1), but had declined to 51 (day 2) and then reached 23 (day 8). Thus, there was an approximate 10 percent decline between day 0 and day 1.

The declines between day 0 and day 2 were about 30 percent and between day O and day S were about 70 percent. By contrast mealybugs receiving spikes containing 25 weight percent ORTHENE® were killed faster in the first few days but eventually (days 5, 8, 13, and 16) the percent kill was about the same as for 15 weight percent spikes.

Reference populations expanded during the 16 day observation period. Initially, the average population was 92. Although there was a small decline to 78 TABLE 4B. NUMBERS OF MEALY BUCS ON SMALL COLEUS IN SECOND EXPERIMENT. THE SMALL COLEUS WERE INFESTED WITH MEALY BUGS AND EXPOSED TO VARIOUS DOSAGES IN ONE INSECTICIDE SPIKE

Dosage

0 15 25

Day of Name of

Sampling Leaf: A B C D X E F G H I X J K L M N X 0 43 84 - 148 92 70 05 11.4 31 82 76 120 91 129 99 152

1 45 94 74 146 90 85 62 123 33 56 72 75 74 118 96 54

2 81 67 74 88 78 22 57 99 26 51 51 95 74 88 62 74

4 91 104 97 146 110 48 34 46 29 70 45 80 62 103 40 111

8 69 121 120 127 112 37 12 21 12 32 23 28 12 36 21 21 13 226 252 219 166 216 3 1 2 0 6 2 6 3 7 1 2 16 324 501 438^† 150^† 353 0 2 0 0 4 1 3 0 16 0 0

mealybugs per plant by day 2, the population had reached 110 by day 4, 216 by day 13 and continued to expand thereafter. Thus, the insecticide spikes were effective in reducing pest populations.

(3 ) Phytopathological Effects Some leaf drop was observed on the coleus plants exposed to the insecticides, but leaf drop also occurred on the references. There did not appear to be any noticeable effects on coleus at the above dosages of one spike.

EXAMPLE NO. 3

The purpose of this experiment was to determine how many insecticide spikes containing 25 weight percent of active ORTHENE® are required to control mites and mealybugs on two species of plants: mums and scheffleras

(A) Procedure

The experimental design consisted of 2 species of plants (mums and scheffleras) X 1 size (large in 6-inch pots) X 3 individual plants X 4 exposures (0, 4,

8, and 16 spikes per large pot) X an average of 7 sampling times. Thus, there was a total of 84 measurements. At each measurement time the number of mites and mealybugs were counted on the upper and lower surfaces of 3 leaves per plant.

Healthy mums and scheffleras were obtained from a nursery in Columbus, Ohio. Large scheffleras were in 6-inch pots and about 20 inches in height. Mums were grown in potting medium comprised of 33 percent vermiculite, 33 percent peat and 33 percent sand.

Scheffleras were growing in a medium whose exact composition was not determined but did consist of a mixture similar to the mums. Plants were maintained with a regular watering regime. Mites were obtained from infested plants at a nursery and subsequently maintained as a colony on nurse plants much as we maintained mealybugs on coleus nursery plants.

(B) Results

The insecticide spikes were effective in reducing mite and mealybug populations on host to zero in most cases (Tables 5 and 6). Doses of 4, 8, and 16 spikes each containing 25 percent of ORTHENE® killed the mites and mealybugs on large scheffleras and on large mums within 24 days after exposure. There were dramatic declines beginning within a day or two after exposure.

(1) Mite and Mealybugs on Scheffleras

Mite populations were reduced from an average of over 30 mites per leaf at day 0 to about 16 mites per leaf by day 24 (Table 5). Plants that received 16 spikes showed more rapid declines in mites than did those plants receiving 8 spikes. The least rapid (slowest) decline in number of mites was observed by plants that had been exposed to 4 spikes. The reference population (0 spikes) showed more than an average of 10 mites per leaf through day 47 then decreased to about 7 by day 72. Thus, the dosages of 4, 8, and 16 spikes worked well to reduce. mite populations.

Mealybug populations were nearly reduced to zero by day 10 (Table 5). There appeared to be no difference in the death pattern for mealybugs as a function of dosage; the pattern of decline for 4, 8, or 16 spikes was similar. By comparison the reference population initially declined then expanded to reach and average of 25 mealybugs by leaf by day 45. By day 73 the mealybugs averaged 11 individuals per leaf, indicating a

decline in the number of individual pests. After 73 days a few mealybugs were observed on the scheffleras; presumably the effectiveness of the ORTHENE® was diminished by day 73 and populations of pesτs could expand.

(2) Mites and Mealybugs on Mums Mite populations were reduced to zero by day 2 with 4, 8, and 16 spike exposures (Table 6). Mite populations began declining within one day after the plants were exposed to the insecticide spikes. Sixteen spikes caused a more rapid decline in pest populations than did 8 or 4 spikes. By contrast, the reference population expanded during the rapid decline of the treated plants, than began to decline reaching an average of 16 mites per leaf by day 21.

Mealybug populations declined on plants treated with 4, 8, and 16 spikes (Table 6). By day 20 no live. mealybugs were observed on mums. There was slightly faster response with 16 spikes compared to 8 spikes. Mite populations were initially low on plants that received 4 spikes and the populations were driven to nearly zero by day 8. Reference populations of mites remained considerably higher than population on the treated plants. By day 21 when all the mealybugs on treated plants were dead the mealybugs mealybug population on reference plants averaged 13 individuals per leaf.

(3) Phytotoxic Effects

Phytotoxicity checks were made 36 days and 40 days, 61 days and 65 days and 120 days and 124 days after healthy scheffleras and healthy mums were dosed with insecticide spikes. In scheffleras (pesticide and no insects) ORTHENE® caused some chlorosis with 4 spikes; chlorosis was found in upper leaves only. With 8 and 15 spikes, chlorosis was found in all leaves. In addition, plants which received 16 spikes had leaves with brown edges and greater leaf drop occurred in plants with 16 spikes than those receiving 4 and 8 spikes. There was an obvious gradual decline in plant health from 0 to 16 spikes of ORTHENE®.

In other scheffleras with insects and pesticides there were signs of mite damage although mites were not present. Also there were signs of phytotoxicity in upper leaves (4 spikes), upper and middle leaves (8 spikes), and all leaves (15 spikes). Mite damage was more obvious in the lower leaves, but ORTHENE® damage was more obvious in the upper leaves. A second effect (noted in this group only) was a curling of the new, tender leaves for plants receiving 8 and 16 spikes. The worst plant in this group was one of the plants receiving 4 spikes; it was mostly dead. In the reference, scheffleras (no insects and no pesticide) were generally worse looking than the above groups of plants. All plants had leaves with brown edges and white speckles. Surprisingly, however, none of the plants in this group was dead.

By 61 and 65 days, scheffleras (pesticide and no insects) were still affected by ORTHEME. With four spikes, approximately half of leaves were chlorotic.

With 8 or 16 spikes, the whole plant was affected. In addition, plants which received the higher doses had curled-up leaves, leaves with brown edges, and leaf drop. Even newer leaves at higher doses (8, 16) were slightly affected. ORTHENE damage appeared to be spreading rather than declining. Scheffleras that had insects and received pesticides had minor evidence of mite damage. Chlorosis and leaf curling were evident at all 3 exposure levels, but were more prevalent at the higher exposures. Newer leaves were healthy-looking for 4 spikes and only minor effects on newer leaves at 8. There are no new leaves with the 16 spike exposed plants. Newest leaves on scheffleras (no insects and no pesticide) were quite healthy looking. Necrosis or death was observed on older leaves. Evidence of mealy bugs, spider mites, and white flies were on most plants. These plants looked healthy and were not dying.

Scheffleras continued to exhibit phytotoxic effects 120 and 124 days after exposure. Those plants receiving 4 spikes showed chlorotic leaf edges on about l/8th of the leaves; new shoots were present. Plants that were exposed to 8 spikes showed new shoots too, but a larger number (about 1/3) of the leaves were chlorotic on the edges. About 1/2 of the leaves were chlorotic in plants that had received 16 spikes and new shoots and leaflets were curled under; the plants still looked unhealthy. By contrast, the reference plants had some leaves dying and new shoots did not look too healty; spider mite damages was in evidence. In chrysanthemums (insects and pesticide) it was difficult to notice differences among 0, 4, 8 to 16 spikes since all plants were in a state of senescence. However, it appeared that more leaves of the plants with 16 spikes were dead than number of leaves for plants with 8 spikes, than those with 4 spikes and than those with 0 spikes.

In reference mums it was difficult to determine differences among 4, 8 and 15-spike treatment. No checks were made on mums at these two observation times because all the plants were dying.

EXAMPLE NO. 4

The purpose of this experiment was to determine the number of spikes containing 25 percent of active ORTHENE needed to protect uninfested plants from colonization by mites and mealybugs when the uninfested plants were placed next to infested plants.

(A) Procedure The experimental design consisted of 2 species of plants (scheffleras and mums) X 2 sizes of plants (large and small) X 4 individual plants X 3 exposures (0, 2, and- 4 spikes per large pot and 0, 1, and 2 spikes per small pot) X 8 sampling times. Thus, there was a total of 384 measurements. At each measurement time the number of mites and mealybugs were counted on the upper and lower surfaces of 2 leaves per plantHealthy scheffleras and mums were obtained from a nursery in Columbus, Ohio. Large scheffleras were in 6-inch pots and about 20-inches in height. Small scheffleras were in 4-inch pots and about 6 inches in height. Large mums and small mums were about 20 inches and 6 inches in height, respectively. Mums were grown in a potting medium comprised of 33 percent sand, 33 percent vermiculate, and 33 percent peat.

Plants were maintained with a regular watering regime. Mites were obtained from infested plants from a nursery and subsequently maintained as a colony on nurse plants much as we maintained mealybugs on nurse plants.

(B) Results

Effect on Mites and Mealybugs The insect spikes were effective in controlling mites and mealybugs on mums (Tables 7 and 8). In general, control of mites was best observed on large as opposed to small mums. Mealybugs populations were suppressed on both large and small mums.

Mites were suppressed by day 17 on large mums (Tables 7 and 8). The population of mites exposed to 4 spikes was slightly lower than the population exposed to 2 spikes. The effectiveness of the insecticide spikes was apparent when the population pattern for 2 and 4 spikes was compared to the population level for 0 spikes. In the latter, mites in mean number greater than 5 per leaf were present on leaves as late as 51 days after exposure began. By contrast mites were suppressed by day 17 on plants receiving insecticide spikes.

Mealybugs were suppressed on both large and small mums (Tables 7 and 8). On large mums the populations of mealybugs were suppressed by day 17. On large mums 4 insecticide spikes per pot suppressed populations of mealybugs by day 17. Two spikes, however, did not kill all of the mealybugs because after 51 days there was still a small population present. The reference (O spikes) showed an average population of around 13 mealybugs at day 51. The average reference population was as high as 61 mealybugs per plant on day 28 compared to 1 or 2 insects per plant for pots that had received spikes.

The pattern of mealybugs on small mums was similar to the pattern .for mealybugs on large mums (Table 7). One spike suppressed mealybug populations, causing their mean number of individuals per leaf to drop from about 36 (day 7) to about 7 (day 28). By day 51 the population had built-up suggesting that the invasion rate of mealybugs from adjacent donor plants was greater than the insecticides ability to control pests. By contrast, the reference plants exhibited mealybug populations higher than those plants that had received protection from spikes. For example at day 17 there were an average of 148 mealybugs per leaf and by day 52 there was a mean of 72 mealybugs per leaf. This latter value was about 5 X as high as that for the treated plant.

TABLE 7. MEAN NUMBERS (N = 6 LEAVES) OF MITES AND MEALY BUGS PER LEAF ON LARGE MUMS. THE LARGE SCHEFFLERAS WERE INITIALLY NOT INFESTED WITH MITES AND MEALY BUGS AND WERE EXPOSED TO VARIOUS DOSAGES OF INSECTIDE SPIKES AFTER BEING PLACED NEXT TO INFESTED PLANTS

Dosages

Mites Kealy Bugs

Day of No. of Sampling spikes: 0 2 4 0 2 4

-5 0.3 0.1 0.3 0 0 0

0 - - - - - -

2 11 4.3 5 0 0 0

6 1 4.7 7.3 26.5 2.3 1

9 10 9.3 3.8 16.3 0.3 1

17 5.2 1.2 0 32.7 2 0

28 13.6 0 0.2 61 0.2 0

51 4.3 0 0 12.8 1 0

TABLE 8. MEAN NUMBERS (N = 6 LEAVES) OF MITES AND MEALY BUGS PER LEAF ON SMALL MUMS. THE SMALL MUMS WERE INITIALLY NOT INFESTED WITH MITES AND MEALY BUGS AND LATER EXPOSED TO VARIOUS DOSAGES OF INSECTICIDE SPIKES AFTER BEING PLACED NEXT TO INFESTED PLANTS

Dosages

Mites Mealy Bugs

Day or No. of Sampling Spikes: 0 1 2 0 1 2

0 - - - - - -

2 - 2 3.4 - 0 0

6 1.8 0.8 0.2 61 36.8 13

9 1.0 0.3 0.8 79 23.3 4.3 17 0.4 0 0 148.4 11.8 4

28 0 0.3 0.3 141.8 7.3 1.5

51 0.2 0 0 71.4 17.5 1.3

The insect spikes were effective in controlling mites and mealybugs on scheffleras (Tables 9 and 10). The most dramatic control was observed with mealybugs on small scheffleras.

Mite populations were reduced to zero by day 51 on large scheffleras that received 2 spikes (Table 9). Scheffleras that received 4 spikes showed an average population of 4 mites per leaf. The reference exhibited an average population of about 8 mites per leaf. By contrast, all mites on small scheffleras were dead by day 17. This was true of plants receiving 0, 1, and 2 spikes. Apparently, small scheffleras do not meet habitat requirements for mites because all the mites died.

By day 51 mealybugs were still observed on large scheffleras (Table 9). Reference populations on day 51 were highest at an average of about 7 mealybugs compared to averages of 2 for two spikes and 4 for 4 spikes. Thus, maly bugs on large scheffleras were partially controlled by the insecticide spikes. By contrast, mealybugs were eliminated on small, treated scheffleras (Table 10). One and two spike exposures resulted in a large decline of mealybug populations by day 28. At that count no mealybugs were observed on small scheffleras. The reference plants, on the other hand, exhibited average populations in excess of 37 mealybugs per leaf from days 6 through 52.

(2) Phytotoxic Effects A phytotoxicity check was made 73 days after healthy scheffleras and mums were exposed to insecticide spikes. Scheffleras that were exposed to 2 spikes showed chlorosis on edges of a few leaves. More of the upper than the lower leaves were affected. Some leaves had brown tips and some leaflets curled at odd angles.

TABLE 9. MEAN NUMBERS (N = 8 LEAVES) OF MITES AND MEALY EUGS PER LEAF ON LARGE SCHEFFLERAS. THE LARGE SCHEFFLERAS WEHE NOT INITIALLY INFESTED WITH MITES AND MEALY BUGS AND UΕRE EXPOSED TO VARIOUS DOSAGES OF INSECTICIDE SPIRES AFTER BEING PLACED NEXT TO INFESTED PLANTS

Dosages

Mites Mealy Bugs

Day of No. of Sampling spikes: 0 2 4 0 2 4

-5 0 0 0.3 0 0 0 0 - - - - - - 2 0.3 0 0.8 0 0 0

6 0.3 3 9.4 9.6 8.6 0.4

9 4.3 5 4.1 2.8 2.3 1.9

17 7.6 13.9 8.6 4.9 9.3 5.3

28 3.6 <1 5.7 4.4 1.7 2.9

51 8.8 0.1 5.1 7.2 2.1 3.9

TABLE 10. MEAN SUMBER (N = LEAVES) OF MITES AND MEALY BUGS PER LEAF ON SMALL SCHEFFLERAS. THE SMALL SCHEFFLERAS WERE NOT INITIALLY INFESTED WITH MITES AND MEALY BUGS AND WERE EXPOSED TO VARIOUS DOSAGES OF INSECTICIDE SPIKES AFTER BEING PLACED NEXT TO INFESTED PLANTS

Dosages

Mites Mealy Bugs

Day of No . of Sampling spikes: 0 1 2 0 1 2

0 - - - - - - 2 - 0.3 0.8 - 0 0 6 0.2 0 0 45.4 49.8 10.3

9 0.4 0.8 0.3 37 13.8 3.8 17 0 0.3 0.4 62.4 3.5 9. 8 28 0 0 0 86.4 0.3 0.3 51 0 0 0 50.2 0 0

Plants that had received 4 spikes shoved chlorosis on edges of some leaves. Some leaves looked healthy while some leaflets curled at odd angles. The reference (no pests and no pesticide) exhibited older leaves with mottled yellow. Some of the new leaves were mishapped and appeared stunted.

Small scheffleras exhibited patterns too. Those plants that received one spike showed chlorotic edges on about one-third of the leaves: some of the leaves were misshapen. Also, new leaves were present and healthy. With 2 spikes, nearly all the leaves had chlorotic edges. Some of the new leaves appeared healthy. On the reference plants (no pesticide) all leaves were brown with yellow areas.

Only small mums were examined because the large mums had died for reasons not related to the pesticides. With one spike the plants appeared to be more healthy than the reference plants. With two spikes the upper third part of the leaves was wrinkled and curl upwards. The reference plants had shoots that were about 13 inches long while the plants exposed to the insecticide spikes averaged 23 inches (dose of 1 spike) and 28 inches (dose of 2 spikes). Thus, the insecticide appears to cause accelerated growth in small mums.

EXAMPLE NO. 5

The purpose of this experiment was to find binders that would produce a product satisfying the objectives of this invention. Initially, attempts were made to cast films from methylene chloride solution containing the polymer and meticulously purified Standak. The insecticide had been isolated from the commercial formulation following a regimen of solvent extraction, repetitive filtration, and recrystallization. However, the data was inconclusive. Therefore, several films incorporating the commercial wettable powder were prepared using the fabrication technique of compression molding.

The data from these investigations appeared more favorable. As shown in Table 11, Elvanol (PVA, Dow Chemical Company), Gelvatol (PVA, Monsanto), Methocel (methylcellulose, Dow Chemical Company), Cellulose Acetate Butyrate (CAB, Eastman Chemicals), Polyox (polyethylene oxide, Union Carbide Company), Carbowax (polyethylene glycol, Union Carbide Company), and Klucel (hydroxypropyl cellulose, Hercules Inc.) were investigated for their potential use as binders to incorporate the wettable powder to form films.

In addition, films of polymer-pesticide were prepared using clay fillers and polymeric plasticizers. The various combinations are listed in Table 12. The results of these investigations indicated that films prepared using a CAB binder alone, had the best qualitative properties of strength, clarity, and flexibility. However, biodegradability within houseplant soil may be at a minimum for spikes prepared using CAB.

Next, plaques ( approximately 1/8" thick) containing the various polymer/insecticide combinations were fabricated by compression molding. These plaques were made using a 4" × 6" positive displacement mold. It was necessary to mold all the plaques, with the exception of those containing the poly(ethylene glycol) and poly(ethylene oxide) at a temperature which was higher than the melt/degradation temperature of the insecticide. The pesticide plaque containing CAB was excessively degraded. Similarly, all the plaques (Table 13) which were molded at the high temperature showed signs of substantial degradation (browning).

TABLE 11 PLAQUE PRESSING WITH INSECTICIDE AND VARIOUS POLYMERS

Polymer, Insecticide

Polymer % by wt. % by wt. Plaque Properties

Polyox 10 80 20^(a) brittle

80 SO 20 brittle & flexible

1105 80 20 brittle & flexible

CW 4000 80 20^(a) weak & brittle

6000 80 20 thin, weak & brittle

14,000 80 20 weak & brittle

Gelvatol 80 20^(b) weak & brittle

Elvanol 80 20^(b) weak & brittle

CAB 80 20^(b) Clear, strong & flexible

Methocel 80 20^(b) strong, but slightly brittle

Klucel 80 20^(b) very thin, flexible but brittle

(a) Polymer processed at 76°C and 10,000 lb. pressure.

(b) Polymer processed at 136°C and 10,000 lb. pressure.

Molded sheets of poly(ethylene glycol) and poly(ethylene oxide) containing Standak appeared both weak and brittle. However, the inclusion of 1% carbon black powder (Raven 5250), and 1% plasticizer/lubricant (Carbowax 4000) significantly increased the strength of the molded poly(ethylene oxide) sheet. In contrast, no apparent increase in strength could be qualitatively seen within the molded poly(ethylene glycol) sheet. Thus, the poly(ethy!ene oxide)/insecticides combination appeared most promising and was subsequently used as a Standak binder during the injection molding studies. A special mold was fabricated to allow for the formation of six 3/16" × 1-15/16" spikes. The spike models were prepared using a Watson-Stiilman injection molder. The polymer/pesticide formulations were molded using an approximate ram pressure of between 500 and 900 psi.

Initially, many different formulations were extruded in order to establish optimum extrusion conditions. The various polymer/insecticide formulations evaluated are listed in Table 14.

As a result of the data obtained from the compression molding studies, poly(ethylene oxide)/pesticide formulations containing varying ratios of carbon black and clay fillers were investigated as possible systemic spike recipes. Table 15 contains the preliminary results from these trials.

It can be readily seen that spikes have been prepared that contain as little as 23% by weight of poly(ethylene oxide). The remaining spike mass consisted of 20% Standak wet~able powder formulation, 1% carbon black filler/extender and 1% carbowax plasticizer/lubricant. It was, however, difficult to injection mold spikes using this formulation and it would be necessary to consider using more PEO to facilitate the eventual preparation of spikes by extrusion. The relatively high cost of PED was the reason for using as little PEO in the spike formulation as possible.

The results using the high melting polymers generally were the same as with the molded sheets. the spikes containing Gelvatol showed definite evidence of degradation while the spikes using poly(ethylene glycol) were weak and brittle. In addition, the formulations with insecticide incorporated in Methocel (with and without a clay filler) and with poly(ethylene glycol) containing carbon black filler, could not be successfully injection molded. The melt fabrication of insecticide spikes requires high temperatures. It is important that the chemical integrity of the insecticide remain intact during this process. Therefore, an experiment was designed to determine whether the model insecticide, Standak, was degraded during the process of melt fabrication by injection molding.

Standak was removed from spikes prepared using the various binder candidates just described by a solvent extraction technique. Spikes were broken into small pieces and placed into a beaker containing a magnetic stirring bar. Approximately 100 ml of anhydrous ether was added and the mixture allowed to stire for 0.5 hours at room temperature. The mixture was vaccuum filtered and the ether allowed to evaporate under low heat. The insecticide residue was then collected and placed in a small glass vial. A 100 ppm aqueous solution was then prepared using 100 mg of the residue.

A 20 microliter sample was injected into a High Performance Liquid Chroraatograph (LC-65 T Chromatography Module). A mobile phase consisting of 15% acetonitrile in deionized water was used at a flow rate

of 20 ml/min. An UV Detector was used at a wavelength of 210 nra to monitor the presence of the insecticide. The results were recorded using a 10 mV recorder at a chart speed of 30 cm/hour and displaying 0.08 absorbance units at full scale (AUFS).

A chromatogram showed that a purified Standak solution used as a control shows component separation withih one minute and insecticide appearance after two minutes. The same tendency can be observed in the chromatograms of the Standak extracted from the spikes prepared using poly(ethylene glycol) and poly(ethylene oxide) as the binders. This indicates that no discernable degradation of the Standak had occurred as a result of melt fabrication using these binders.

EXAMPLE NO. 6

A primary objective of this experiment was to identify an optimum composition for the fabrication of the Systemic Insecticide Spike using the predicted manufacturing technique of melt extrusion.

Since the experiment was not concerned with the effects of the insecticide, extrusion studies were performed without a systemic insecticide within the formulation. Table 16 contains a list and the specific quantities of the ingredients used in the formulations of this experiment.

Non-toxic spikes were melt fabricated by extrusion utilizing two grades of PEO (WSR N-750 and WSR N-80), a single lubricant (Carbowax 4,000) and several types of filler (spray satin clay, sized corn cob and Raven 5250 carbon black). The preferred ingredients were weighed into a paper cup (4 ounce) and mixed by hand using a wooden tongue depressor. The mixture was subsequently fed into the water-cooled hopper of a single TABLE 16. EXTRUDED NON-TOXIC INSECTICIDE SPIKES

Spike Formulations

Composition Hinder PEO^(a)Crade, Quantity, % Clay,^(b) Lubricant,^(c) Colorant,^(d) Diameter,

WSRN- % % % inches Code

80 97.5 _ 2 0.5 0.240 1

80 97.5 - 2 0.5 0.195 2

80 52.5 45 2 0.5 0.240 3

80 52.5 45 2 0.5 0.195 4

80 51.0 45 2 2.0 0.240 5

80 51.0 45 2 2.0 0.195 6

80 37.5 60 2 0.5 0.240 7

80 37.5 60 2 0.5 0.195 8

80 35.5 62 2 0.5 0.240 9

80 35.5 62 2 0.5 0.195 10

80 32.5 65 2 0.5 0.240 11

80 32.5 65 2 0.5 0.195 12

80 30.5 67 2 0.5 0.240 13

80 30.5 67 2 0.5 0.195 14

80 27.5 70 2 0.5 0.240 15

80 27.5 70 2 0.5 0.195 16

750 51.0 45 2 2.0 0.240 17

750 41.0 55 2 2.0 0.240 18

750 37.5 60 2 0.5 0.240 19

750 27.5 70 2 0.5 0.240 20

750 22.75 75 2 0.25 0.240 21

750 17.75 70 2 0.25 0.240 22

(a) Poly(ethylene oxide); Dow designation for Water Soluble Resin having a narrow molecular wυJght distribution, Dow Chemical Company, Midland, MI.

(b) Spray Satin, Englehard Minerals & Chemicals Corp., Iselin, NJ.

(c) Poly(ethylene glycol) having a molecular weight of 4,000; Carbowax 4,000, Dow Chumlcal Company, Midland, MI. (d) Ferro V-11655, Mixtureof Cobalt, Chromium, Titanium and Zinc Oxides, Ferro Colors, Cleveland, Ohio.

screw (20:1 L/D) extruder (5rabender Extruder, C. W. Brabender Instruments, Inc., South Hackensack, NJ). The barrel temperature of the extruder was maintained between 60° and 70°C by therrr.ostatic control of two internal heaters. The die temperature was maintained between 70-80° using an externally applied heating tape attached to a laboratory rheostat (Variac). Two dies were used having inside diameters of 0.240 and 0.195 in, respectively.

The extruded rods were sliced into two inch spikes while still warm. The physical properties of fabricated spikes of varying composition were subsequently determined. Mechanical tests were performed on the spikes to approximate some of the physical stresses that could be imposed upon the spike during fabrication, packaging, shipping, handling and use.

Tensile Strength In the extrusion process, the extruded rod exits the die while still at a relatively high temperature. The rod should have a sufficient hot strength to allow a tensile stress to be applied during the drawdown and/or pulling process of the conveyor on the way to the cutters. Spikes must also display satisfactory strength properties when cool to avoid any undesirable damage to the product during packaging, shipping and use. For these reasons, extrusion--formed spikes were tested in order to determine their tensile strengths at both elevated and room temperatures using an Instron Testing Machine ( Instron Engineering Corp., Canton Massachusetts) having an electrically heated oven (Instron Oven, Instron Engineering Corp., Canton, Mass.). Procedure. The tensile strength of extruded spikes were determined at 23 and 70 C using an imposed stress of 0.2 inches/minutes. It is important to note that the oven temperature for the hot tests varied in the range between 60 and 70 C as a result of the heat loss which occurred from opening and closing the oven door during placement and removal of a spike. The actual tensile testing was begun only after the oven was allowed to come to constant temperature (approximately five minutes). Three replicate samples of spikes containing two PEO grades were tested and the results, in pounds, were averaged. These results are listed in Table 17 along with the results of tensile tests performed on spikes at room temperature.

All of the results are expressed in terms of the pounds of tensile stress necessary to break a spike. This convention should help in understanding the physical properties of fabricated spikes rather than filled polymer spikes. It also must be kept in mind that these graphs depict trends and are not absolute measures. Each of the depicted data points represents averages of 3 to 5 sample replicates and can be considered as a reliable indication of trends in physical property variations.

Results. A heated spike apparently responds to tensile stress in a very different manner than a spike tested at room temperature. The spikes containing WSR N-80 which have been exposed to temperatures approaching 70 C display low tensile strengths. However, increasing the quantity of filler in a spike from 45 to 70% by weight caused a corresponding increase in the tensile strength at break from approximately zero to 2.0 pounds (p), respectively. On the other hand, the tensile strength at room temperature generally decreased TABLE 17. TENSILE STRENGTH OF NON-TOXIC SPIKES

Spike Formulation Tensile Strength.^(b) pounds/spike

Code^(a) at 23° C at 70° C

1 91.40 ± 6.83 Too Soft to Evaluate 2 45.92 ± 9.39 Too Soft to Evaluate 3 31.20 ± 3.55 0.19 ± 0.12

4 25.20 ± 4.56 0.04 ± 0.01 5 45.13 ± 5.66 0.59 ± 0.51 6 28.70 ± 3.23 0.09 ± 0.03

7 36.80 ± 4.86 4.55 ± 1-23

8 24.10 ± 2.63 0.40 ± 0.05 9 36.88 ± 1.80 5.90 ± 0.42

10 29.50 ± 0.53 0.58 ± 0.08 11 24.33 ± 3.12 4.54 ± 0.31 12 30.00 ± 2.57 1.09 ± 0.17

13 28.40 ± 5.38 3.18 ± 1.09

14 23.80 ± 5.08 1.01 ± 0.05 15 29.00 ± 3.94 4.06 ± 1.13

16 25.00 ± 7.80 1.97 ± 0.35 17 43.88 ± 3.86 0.22 ± 0.09 18 40.40 ± 8.38 0.22 ± 0.10

19 48.23 ± 6.84 0.57 ± 0.15 20 58.60 ± 5.63 2.00 ± 1.51 21 26.38 ± 5.33 Too brittle to evaluate 22 21.75 ± 3.07 Too brittle to evaluate

(a) Formulation is identified in Table 16.

(b) Value is average of 3 to 5 spikes. from 91.4 p at 2.5% filler content (lubricant and colorant) to approximately 29.0 p at a filler content of 70%. Discussion. One possible reason for these apparently contradictory trends can be seen upon consideration of the molecular structure of the PEO. Chain mobility and the relaxation of internal stresses could be induced as the polymer approached its characteristic melting temperature and near zero tensile strength in the heating chamber. Chain relaxation could cause sample contraction which would appear as an increase in tensile strength. In addition, the application of a small tensile stress could induce chain alignment. Some of the energy of stress could then be transferred to the filler.

This would be realized as an apparent increase in the strength of an extruded spike in the tensile direction. Increasing the filler content should then result in an increase in hot tensile strength up to the point where spikes could no longer be fabricated.

This same reasoning can be used to predict the effects of pulling an extruding rod (in the process of colling) down a conveyor to the cutters. An increase in an initially low hot tensile strength can be expected from increasing the quantity of filler. However, this trend must be balanced against the trend to decrease the tensile strength with increased filler content when stressed at room temperature. In this latter instance, the clay acts as a true filler and serves to diminish the overall strength of the polymer. A recommendation based upon the results of these tests would be to prepare spikes having a filler content of between 60 and 70% by weight. It should be remembered that the insecticide to be used in the formulation was considered as a portion of the filler in these studies. A usable spike having 50% filler and 20% insecticide would be analogous to the 70% filler referred to during this discussion. This approximate formulation appears at this time to both minimize the decrease in ambient tensile strength as a result of including filler as well as to maximize the poor tensile strength of an extruding rod when hot.

Flexural Strength

The inherent flexural strength of a fabricated spike need only be measured at room temperature since the predictable bending stress that might be imposed upon a spike should occur solely during placement into plant soil. The data is listed in Table 18.

The flexural strength was determined using the 3 point loading apparatus of the Instron and is recorded as an average value of 5 replicates in terms of pounds of flexural stress required to break a spike. The rate of applied bending stress was 0.2 inches per minute.

It can be seen that increasing the filler content of a spike is detrimental to the ultimate flexural strength. Fortunately, even the most highly filled spikes apparently displayed adequate qualitative strength for placement within moist soil. It should be noted that the spikes prepared to a smaller diameter had proportionally less mass and were subsequently more susceptible to brittle fracture when subjected to a flexural stress. However, in either situation there is little change in the apparent flexural strength as the filler concentration is increased from 40 to 70% by weight. A combination of the information learned from the test data and qualitative observations indicates that a spike which contains as much as 70% filler may be an acceptable formulation. The inclusion of this approximate quantity of filler within a spike formulation should allow for TABLE 18. PHYSICAL PROPERTIES OF NON-TOXIC SPIKES

Physical Properties (b)

Spike Foraulation Flexural Strength, Inpact Resistance

Code^(a) pounds/spike foot-pounds/spike

1 29.13 ± 10.31 1.33 ± 0.29

2 9.66 ± 1.00 0.54 ± 0.09

3 7.28 ± 0.68 0.23 ± 0.09

4 4.30 ± 0.41 0.33 ± 0.03

5 9.95 ± 0.30 0.33 ± 0.09

6 5.36 ± 0.53 0.27 ± 0.04

7 7.16 ± 0-96 0.13 ± 0.03

8 4.68 ± 0.60 0.08 ± 0.01

9 8.14 ± 0.58 0.12 ± 0.03

10 5.48 ± 0.04 0.08 ± 0.02

11 5.30 ± 2.07 0.07 ± 0.01

12 5.30 ± 0.33 0.06 ± 0.01

13 10.06 ± 0.84 0.07 ± 0.01

14 5.60 ± 0.25 0.06 ± 0.01

15 11.18 ± 0.76 0.08 ± 0.01

16 5.94 ± 0.23 0.05 ± 0.003

17 9.36 ± 1.48 0.40 ± 0.08

18 7.50 ± 0.67 0.21 ± 0.04

19 7.32 ± 0.33 0.18 ± 0.01

20 9.60 ± 1.01 0.06 ± 0.01

21 5.26 ± 0.75 0.03 ± 0.01

22 4.88 ± 0.53 0.03 ± 0.01

(a) Formulation is identified in Table 16.

(b) Value is average of 3 to 5 spikes. the preparation of a product having acceptable strength at a minimum cost.

It should once again be pointed out that the insecticide has been considered as filler for the purpose of the discussion. The data contained in Table 19 indicates spikes can be filled to 70% with filler and insecticide and still retain adequate flexural strength. Although these spikes were prepared by the technique of injection molding rather than extrusion, similar conclusions can be made. Poly(ethylene oxide) can be highly filled during a melt fabrication process. Indications are that the inclusion of a wet-table powder insecticide (Orthene) formulation as part of the filler content has little apparent effect upon the ultimate physical properties of the product.

Impact Resistance

Fabricated spikes may foreseeably be subjected to many impact stresses. Spikes could be impacted during the packaging process as well as during the shipping or storage procedures. Therefore, it is important to identify a formulation which can withstand most of the "normal" impact stresses to be encountered. A description of the trend in impact resistance as a function of filler content should serve as a good starting point since data concerning the service life stresses for a spike are presently unavailable.

The resistance to impact displayed by standard non-toxic test spikes is data contained in Table 18. The impact resistance was determined using an Impact Tester (Testing Machines, Inc., Mineoia, NY). Each 2-inch spike specimen was positioned vertically within a brass holder using a locking screw. It was subsequently impacted using a 2-lb pendulum weight and the 8

results recorded for an average of 3 to 4 spikes in terms of foot pounds of force used to break a spike. The impact strength displayed by fabricated spikes generally decreased as the quantity of filler included within the polymer increased. It should be remembered that spikes were no longer readily fabricable as the filler content of the original mix was increased beyond 70%. As a result, the strength data can only be presented to describe spikes thar contain as much as, but no greater than, 70% by weight filler (spray satin clay).

There is little or no discemable variation in the minimal strength as the filler content is varied within the range of 60 to 70%. A qualitative assessment of these highly filled polymer systems provides the basis for a recommendation that filler can be included to as much as 70% by weight of the formulation and still maintain an acceptable strength for resistance to impacts which may be encountered within a package. Specific tests will have to be performed using the packaging equipment available to International Spike in order to determine the ability of a fabricated spike to withstand the impacts and abrasive action imposed by the equipment. Further adjustments in the filler content can be made at that time.

Summary

The results of the physical testing portion of the research effort show that a formulation containing poly(ethylene oxide) and as much as 70% of an inert clay filler and insecticide could yield spikes displaying adequate physical properties at a minimum dollar expenditure for materials. The wettable powder form of the insecticide has been considered to be equivalent to a filler. EXAMPLE NO . 7

This experiment was conducted to identify and develop the procedure coating the pesticide spike.

Procedure

The most appropriate laboratory procedure for the preparation of coated spikes containing an active systemic insecticide was by dipping preformed spikes into a driable solution of coating polymer in a volatile solvent. Each coating polymer candidate was placed in three candidate solvents in order to identify a usable solution viscosity and drying time. Attempts were made to prepare coating solutions having initial coating to diluent solvent weight ratios of 50:50; 25:75 and 10:90, respectively. The latter was found to be most suitable to prepare fast-drying polymer solutions.

Air-driable alkyd or unsaturated polyester coatings were investigated and solvent was used as a dilutent to lower the initial viscosity. Coated spikes were prepared by dipping preformed (injection molded) non-toxic spikes into the polymer solutions for approximately three seconds and subsequently placing them in an oven (40° C) to dry. Drying spikes were periodically tested in the oven in order to discern the time after application necessary to provide a coating which was tack-free to touch.

Drying Time

Drying time is an important consideration since it could be the rate limiting step in the production process. It is desirable that the coating dry in the time it would take to travel down the conveyor to the cutters. In addition, spikes may have to be kept separate to avoid agglomeration during the drying phase. This may be hard to attain with long drying times. Therefore, the shortest drying time is the most desirable.

A complete catalogue of the coating candidates is contained in Table 21. A 10% solution of cellulose acetate (AC 6555, Eastman Chemical Products, Kingsport, TN) in ethyl acetate dried to form a tack-free coating in 1.0 to 1.5 minutes in an oven at 40° C. This rate proved to be the fastest of these tested. An alternate choice is a 10% solution of poly(vinylacetate) (Vinac

B-15, Air Products, Allentown PA) in ethyl acetate which dried in the same approximate time. The use of alkyd resins as a coating does not seem to be appropriate at this time. The resin must dry via a slow chemical reaction. In contrast, the solvent need only evaporate from a polymer solution when cellulose acetate is used. The cellulose acetate coating formulation is preferable to the poly(vinyl acetate) since the former is a derivative of a natural product while the latter is commercially prepared using petroleum derived chemical feedstock. Of course, the degradation products of both should be harmless to the planrs as well as animals. For instance, cellulose acetate should degrade to the natural fiber cellulose and eventually to glucose. Similarly, poly(vinyl acetate) should yield poly(vinyl alcohol) which is an EDA approved food additive. Both coatings could also yield acetic acid as a by-product. Acetic acid is the main ingredient in edible vinegar and is considered to be harmless to the environment at the quantities found on the spike.

Coating Thlcl-αiess

Coating thickness should have important effects upon the ultimate efficiency of the spike product. The thickness of the coating should directly affect the initial delivery rate by altering the diffusion path length. In other words, it can be expected that the thicker the coating barrier, the slower the initial rate of release of active ingredient from the spike and into the potted plant soil. The following discussion contains a description of the experimental task designed to identify a procedure which could be used to coat spikes in order to prepare a reproducible coating thickness. Subsequent studies should attempt to identify the effect of variations of coating thickness on the release rate of toxicant from the spike product.

A 10% solution of cellulose acetate in ethyl acetate was used as the test coating system. The average diameter of preweighed spikes (10) was determined using a micrometer having an accuracy of 0.01 mil. The sized spikes were subsequently pierced at one end with a straight pin and suspended into the coating solution for approximately three seconds via attachment to a string. The spikes were removed from the solution and allowed to dry in an oven at 40 C for 75 to 80 seconds. The width of the coated spike was then measured and found to be approximately one mil greater. On the other hand, the bottom portion of a suspended spike developed a greater thickness of between 1.5 and 2.0 mil due to excess buildup of polymer from flew while drying.

A subsequent experiment was performed in order to double the coating thickness. The desired increase in coating thickness was obtained by dipping spikes for three seconds into the coating solution, removing them for three seconds, dipping once again for another three seconds and finally transferring them to an oven to dry. Spikes which had been coated to an overall increase in diameter of 2 mil were found to have increased in weight by an everage of 0.07 g. In other words, approximately 7 lbs of cellulose acetate in 63 Ibs of recoverable ethylacetate would be necessary to apply a one mil coating to 100 lbs of insecticide spikes.

EXAMPLE NO. 8 The object of this experiment was to determine the rate and profile of delivery of active ingredient from products made in accordance with this invention to the potted plant soil.

Several spike formulations were prepared and the rate of release of the insecticide from the spike subsequently determined. An initial fast rate of release has been observed. This was followed by a slower delivery rate. In addition, the insecticide was apparently exhausted from the spike within a 25 to 30 day period. It must be realized that the actual duration of biological effectiveness of the spikes can only be determined during the bioassay phase of the project. The laboratory tests that are discussed herein are designed to provide estimates of the experimental direction for the identification of an optimum formulation.

The following sections contain descriptions of the procedures used and results obtained from the tests designed to determine the relative release rate profiles of the insecticide from the spikes.

Preparation of Insecticide Spikes

The insecticide spikes which were prepared contained either the commercial wettable powder formulation of Standak (Union Carbide Corp.) or Orthene (Chevron Chemical Company) as the active ingredient. The former was included at a weight percentage of 20% while the latter at 10, 20 or 30% by weight of the spike. Second, the cumulative weight of insecticide and clay was maintained at a constant level. Therefore, any reduction in the quantity of insecticide within a fab ricated spike was balanced with a corresponding increase in filler content. Third, all spikes were prepared to include a single colorant (green, Ferro). It was later determined from the marketing studies that brown or red-brown could be more desirable colors to the consumer. However, the actual identity of the colorant is not presently perceived as important to the preliminary experimental determination of the relative release rates. Finally, spikes were coated with cellulose acetate to yield either a one or two mil increase in diameter. Only spikes which had been coated to the former thickness were tested in order to determine relative release rates. The spikes having the larger coating were retained for possible future evaluations using the laboratory and/or bioassay techniques.

Table 21 contains a description of the eight formulations prepared for the release rate studies. The PEO, Carbowax, insecticide formulation, clay and colorant were placed together in a 4-ounce paper cup and dry-mixed until qualitative homogeneity was apparent (approximately 15-25 seconds) using a wooden tongue depressor. The mixture was then fed directly into the heating chamber of the Watson-StiIiman Injection Molder and maintained at a temperature of 86-92 C for five minutes. A ram pressure of 900 psi was applied to force the flowable mixture into the preheated mold (60 C, approximately 10 minutes). The mold was capable of producing six spikes which were each two inches in length and having an outside diameter of 0.195 inches.

The hot mold was removed from the press and allowed to cool for approximately one minute. The spikes were removed from the mold and excess film cut away using a straight-edge razor blade. Next, some of the spikes were coated by suspension from straight pins and dipping into a 10% solution TABLE 24. PREPARATION OF COATING SOLUTIONS ^(a)

Formulation Results ^(b)

Coating Solution Drying

Trade Name Composition Vendor solvent compositlon,% Solution Time, min.

XP-7419 Alkyd/acrylic Cargill, Chemical Ethylacetate 50 Misclble^(c) 5 copolymer Products Division, " 25 " 5

Minneapolis, MN Isopro IIpyl alcohol 50 " 5 " 25 " 5

Heptane 50 " 13 " 25 " 15

Kelso 3907 Alkyd resin Textron Inc., Ethylacetate 50 Misc l b l e 45-50

Spencer Kellogg " 25 " "

Division, Boston, Isopropyl alcohol 50 " "

MA " 25 " "

Heptane 50 " " " 25 " "

Butvar B-76 Poly(vlnylMonsanto, St. Ethylacetate 50 Not Soluble - butyral) Louis, MO " 25 Soluble 2 Isopropyl alcohol 50 Not Soluble - " 25 Soluble 3

Heptane 50 Not Soluble - " 25 " " -

Vlnac B-15 Poly(vlnylAir Products, Ethylacetate 50 Gel - acetate) All entown, PA " 25 Viscous 1.5-2 10 good 1.5-2 Isopropyl alcohol 50 Not Soluble - " 25 Not Soluble -

Heptane 50 " " - " 25 " " -

Cellulose Cellulose Eastman Chemical Ethylacetate 50 Gel -

Estor CA acotato Products, Kings" 25 Viscous 1.5-2

6555 port, TN 10 good 1.0-1.5 Isopropyl alcohol 50 Not Soluble - " 25 " " -

Heptane 50 " " - " 25 " " -

(a) Preliminary test designed to determine compatible coating and solvent. (b) Spikes were placed in an oven at 40° C to dry. (c) Dilutable liquid resins.

of cellulose acetate in ethyl acetate solution for a period of three seconds. The dipping procedure was repeated in order to obtain twice the coating thickness. The wet spikes were then placed in an oven at 40° C for 75 seconds, removed and set aside for determination of the relative release of insecticide from the composite product.

General Test Procedure A 1:1 weight ratio mixture of alpha-cellulose fiber mat (Hawkesbury Sulfite, International Pulp Sales Company) and distilled water (20 g) were shredded in a Waring Blender. The pulp (40 g) was then placed in a beaker (400 ml) in order to simulate houseplant soil having a 25% moisture content. Preweighed spikes were individually placed in the simulated houseplant environment and the top covered using Saran plastic wrap doubly secured with a rubber band. A spike was removed from each of eleven beakers after 0.25, 1, 2, 3, 5, 7, 10, 13, 16, 20 and 25 dys. The quantity of residual nitrogen was then determined and used as a measure of the amount of pesticide released. The specific analytical procedures which were used will be discussed in the following sections as well as the development of the testing procedure and the knowledge gained concerning the mechanism and the efficacy of the performance of the spike.

Uncoated Spikes. An initial attempt to determine the rate of release of insecticide from a spike was carried out using an uncoated spike containing Standak. Complete dissolution of the spike was apparent in water after 24 hours.

A total of 22 beakers containing pulp were prepared in order to accomodate 11 spikes containing Orthene (85% by weight active ingredient wettable powder) in PEO WSR N-80 and an equal number of spikes were prepared having 45% of the weight as clay filler. The spikes were not coated. Each preweighed spike was inserted into the beaker and care taken to insure complete coverage with pulp. Each spike was to be removed for analysis according to the predetermined time regimen. Ecwever, the spikes were nearly completely dissolved by the end of the first day of exposure. Therefore, the experiment was discontinued. Valuable information can be gleaned from this brief experiment. An average houseplant soil having a moisture content of 25% would likely be sufficient to allow for complete dissolution of a plant spike within one to two days. Thus, all of the insecticide would be released within that short time. This initial high dose of insecticide could meet the general criteria of fast release for the desired short-term kill (within a 24 to 48 hour period) However, the duration of effectiveness of the formulation could not be expected to substantially exceed the actual duration of the active ingredient itself.

These results indicated that the application of a biodegradable coating to the spikes could serve two functions. First, the coating could provide a safety buffer between the active ingredient residing on the surface of the solid formulation and the person handling the device. Second, the coating could slow the rate of release of insecticide from the fastiy degradable spike. The following sections describe the experiments designed to determine the release rate of the insecticide from coated spikes.

Coated Spikes. Figures 8-10 graphically present the data obtained from the experiments designed to determine the relative difference in the rates of release of coated spikes containing Standak and coated spikes containing various loadings of Orthene. It was found that the one mil cellulose acetate coating significantly extended the physical lifetime of the spikes containing insecticide to at lea'st 25 days after application. In other words, relatively intact spikes could be removed from the simulated release environment up until this time but not after. This improvement afforded a method to determine the quantity of insecticide released to the surrounding moist pulp. Spikes were removed at the predetermined times described earlier from the simulated soil environment using tweezers and placed in preweighed glass vials. Any large quantities of residual pulp adhering to the spikes was carefully removed and the vials set in an oven (40° C) to dry. The vials were removed after a constant weight was attained and the residual nitrogen determined using the standard kjeldahl digestion technique. The quantity of nitrogen remaining in the spike after exposure to the moist pulp could be used to determine the quantity of insecticide which was released to the test environment.

The data displayed in Figures 8, 9 and 10 should be viewed as trends indicative of the relative release rates and profiles of coated spikes. For instance, Figure 8 displays the data from an experiment designed to discern the relative release rates of coated spikes containing 20% Standak or Orthene. The apparent difference in the rate of loss of insecticide from the spikes may not exist. It may, in fact, be attributable to the scatter of the data points.

The initial trend for a fast release of insecticide from the spike is generally followed by a slower delivery of active ingredient. The initial trend for a fast release of active ingredient provides sufficient systemic insect toxicant to a plant to cause a significant reduction in the size of any existing pest population. The subsequent change in trend towards a slow release could, then, act as a maintenance dosage to ensure that re-infestation will not occur during a desirable period of effectiveness of 30-60 days.

A second important point is that dip-coated spikes prepared from a water-soluble, thermoplastic binder containing an inert filler and a wettable powder formulation of either Standak or Orthene can maintain their physical form for up to 25 days in a standard experimental situation. This is in comparison to the short, one to two day, lifespan of uncoated spikes. It is important to note that the coating remained nearly intact after both the binder and insecticide content had been exhausted. This can be attributed to the fact that cellulose acetate is not water soluble. However, it is biodegradable and the rate of dissappearance should be evident in a soil environment where microorganisms can act. The rate at which water diffuses through the coating into the active matrix and back out through the coating to the pulp environment probably determines the release rate of the insecticide from the spike. The striking contrast in water solubility of the two insecticides can be misleading when interpretting the data displayed in Eigure 8. The water present in the release environment could be considered as a huge excess. Thus, a sufficient quantity exists to completely dissolve the small amounts of insecticide encountered within a spike.

The data contained in Figure 9 displays another important feature of the way in which the eventual effectiveness of the insecticide spike could be controlled by varying the loading of active ingredient in the initial formulation. Increasing the relative loading levels within coated spikes from 10 to 30% by weight does not apparently result in a corresponding change in the relative release rate.

Of course, this does not mean that there is no change in the quantity of insecticide that is released. The results of the experiment indicate that a change in the initial loading of insecticide in a spike will result in a corresponding change in the cumulative release of insecticide. This can be seen in Figure 10 where the quantity of insecticide released from the spike with time is plotted. A general trend can be seen in which increasing the initial loading results in an apparent linear increase in the quantity of insecticide released. In other words, varying the initial loading of insecticide in a spike will affect the quantity of insecticide which is available to a plant at any given time. This should provide a means to predictably alter the apparent duration of effectiveness.

Many changes and modifications will occur to those skilled in the art upon studying this disclosure. All such changes and modifications that fall within the spirit of the invention defined by the appended claims are intended to be included within its scope.

Claims

WE CLAIM:

1. A product for controlled release of a systemic pesticide into the soil, said product comprising: a systemic pesticide; and a matrix for holding said systemic pesticide said matrix comprising a solid hydrophylic polymeric binder, said binder being water soluble so as to allow moisture in the soil to erode said matrix causing an initial rapid release of the systemic pesticide from said product into the soil and subsequent slower controlled release of said systemic pesticide.

2. The product of Claim 1 wherein said pesticide is a systemic insecticide.

3. The product of Claim 1 wherein: said systemic pesticide is stable at the fabrication temperatures of the product, has a sufficient solubility in water to be dissolved and transported to and in the sap of a plant, remains stable and active within the normal ph ranges found in both soils and plants, and has the ability to kill desired pests, and wherein said binder inflicts no phytotoxic effects on plants, is capable of being infinitely mixed with the systemic pesticide, does not react with said pesticide in the manner that destroys the function of each in said product, has its softening temperature below the decomposition temperature and imparts a sufficient strength to the fabricated product to maintain it substantially intact during packaging, storage, shipment or insertion into the soil.

4. The product of Claim 1 wherein said pesticide is dimethyIphoshate of 3-hydroxy-N-methyl-cis crotonamide.

5. The product of Claim 1 wherein said pesticide is O,O-dimethyl-O-(z-methylcarbamoyl-1-1-methyl vinyl)- phosphate.

6. The product of Claim 1 wherein said pesticide is O,O-dimethyl s-(N-methylcarbamoylmethyl) phosphorodithioate.

7. The product of Claim 1 wherein said pesticide is O,O-dimethyl acetylphosphoroamidthioate.

8. The product of Claim 1 wherein said pesticide is O,s-dimethylacetylphosphoroasmidothioate.

9. The product of Claim 1, 4, 5, 6, 7 or 8 wherein said binder is polyethylene oxide.

10. The product of Claim 1, 4, 5, 6, 7 or 8 wherein said binder is poly(ethylene glycol).

11. The product of Claim 7 wherein said systemic pesticide comprises from about 70 to about 30 weight percent of said product and wherein said binder is poly(ethylene oxide) comprising from about 30 to about 70 weight percent of said product.

12. The product of Claim 8 wherein said systemic insecticide comprises from about 70 to about 30 weight percent of said product and wherein said binder is poly(ethylene glycol) comprising from about 30 to about 70 weight percent of said product.

13. The product of Claim 12 further comprising: from about 0 to about 5 weight percent of a plasticizer; from about 0 to about 70 weight percent of a filler; from about 0 to about 2 weight percent of a colorant, said plasticizer, filler and colorant being intimately dispersed in said binder and in said insecticide; and from about 2 to about 20 weight percent of a biodegradable coating covering the surface of said product.

14. A systemic pesticide spike, comprising: a hydrophilic water-soluble poly(ethylene oxide) polymer; and a systemic insecticide, said polymer forming a matrix holding said systemic insecticide therein such that said pesticide is upon insertion into the soil initially rapidly released into the soil by action of the soil moisture and is subsequently controllably released from said matrix by the moisture from the soil, said spike being drivable into the soil without breaking or shattering.

15. A systemic insecticide spike of Claim 14 further comprising: from about 0 to about 5 weight percent of a plasticizer; from about 0 to about 70 weight percent of a filler; from about 0 to about 2 weight percent of colorant; and from about 0 to about 20 weight percent of a protective coating.

16. A process for making a sustained release systemic pesticide product, comprising the steps of: (a) mixing from about 25 to about 99 weight percent of a polymeric binder, from about 1 to about 75 weight percent of a systemic pesticide to form a dry mixture;

(b) applying sufficiently high temperature and pressure to said dry mixture to melt it to a desired shape.

17. The process of Claim 16 further comprising the step of applying a coating to the surface of said product.

18. A sustained release pesticide product produced by the process of Claim 16.

19. A process for making a sustained release systemic insecticide product comprising the steps of: (a) mixing approximately 25 to 95 percent by weight of a polymeric binder, 5 to 75 percent by weight of a systemic pesticide, 0 to 70 percent by weight of a filler, 0 to 5 percent by weight of a plasticizer; 0 to 2 percent by weight of a colorant; (b) heating the dry mixture obtained in (a) until it melts;

(c) shaping said melted mixture to form a spike;

(d) allowing the spike at least partially to solidify;

(e) coating the spike with a solution of a biodegradable polymer.

20. A sustained release insecticide product made in accordance with the process of Claim 19.

21. A method for eliminating pests from a plant comprising: inserting into the soil in the vicinity of the roots of said plant a product comprising a systemic pesticide and a solid water soluble, hydrophilic polymeric binder, said binder forming a matrix enclosing said systemic pesticide such that the moisture of the soil dissolves said matrix and said binder and rapidly releases a sufficient amount of said systemic pesticide from said matrix into the soil to kill at least a significant number of pests and subsequently controllably release said systemic pesticide to allow the plant to continuously adsorb it into its sap to kill the remaining pest and to prevent reinfestation.

22. The method of Claim 21 wherein said systemic insecticide is O,S-Dimethylacetylphosphoroamidothioate.

23. The method of Claim 21 wherein said systemic insecticide is O,S-Dimethylacetylphosphoroamidothioate.

24. The method of Claim 21, 22 or 23 wherein said binder is poly(ethylene oxide).

25. The method of Claim 21, 22 or 23 wherein said binder is poly(ethylene glycol).