WO1997017830A1

WO1997017830A1 - Method of controlling pests and pathogens in growing media with pulsed electromagnetic energy

Info

Publication number: WO1997017830A1
Application number: PCT/US1996/016912
Authority: WO
Inventors: Manuel C. Lagunas-Solar; Jeffrey Granett; James D. Macdonald
Original assignee: The Regents Of The University Of California
Priority date: 1995-11-13
Filing date: 1996-10-22
Publication date: 1997-05-22
Also published as: AU7465796A

Abstract

A method of controlling pests and pathogens in soil and other growing media. Growing media containing undesired pests and pathogens is treated with a plurality of short duration energy pulses from an electromagnetic source. The frequency of the source is chosen such that the electromagnetic energy penetrates the growing media and excites molecules in the pests and pathogens, but does not excite water or other molecular structures in adjacent plant growth. The pests and pathogens are thus selectively heated and destroyed without harming adjacent plant growth.

Description

METHOD OF CONTROLLING PESTS AND PATHOGENS IN GROWING MEDIA WITH PULSED ELECTROMAGNETIC ENERGY

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention pertains generally to controlling or eliminating pests and pathogens in soil, and more particularly to a method of treating bare or planted soil containing undesired organisms with electromagnetic energy wherein the undesired organisms are selectively or preferentially destroyed without harming desirable plant material adjacent to the treatment area. 2. Description of the Background Art

In the United States, changes in public attitudes towards the use of chemicals to control pests and pathogens have resulted from increased concern for food safety and preservation of environmental quality. Agricultural pesticides have been used extensively and intensively since the 1940s, resulting in the largest and safest food supply the earth's population has ever seen. However, concerns about this technology have continuously increased as a result of environmental contamination and degradation such as groundwater contamination and ozone depletion, as well as sporadic episodes of acute poisonings. Popular awareness and attitudes concerning these problems are reflected in ever-increasing regulatory actions targeting agricultural pesticides. As the regulations have increased, the availability of agricultural pesticides has decreased. This has imposed new technological demands on agriculture and may create new barriers to the international trade of foods and agricultural commodities because of quarantine regulations of our trading partners.

In order to address the health and environmental concerns with the management, elimination or eradication of agricultural pests and pathogens, non-additive and non-residual methods of controlling organisms in a variety of soils and plant material using thermal energy have been developed. For example, U.S. Patent No. 5,141,059 issued to Marsh on August 25, 1992 discloses use of microwave energy directed into the depth-growing area of crop fields to destroy weed, plant and insect cells prior to planting of the crop. U.S. Patent No. 2,784,286 issued to Dillon on March 5, 1957 discloses use of an electrical heating element in the soil to destroy chance seeds and harmful bacteria. U.S. Patent No. 4,092,800 issued to Wayland, Jr. et al . on June 6, 1978 discloses use of microwave transmitters operating between 300 MHz and 300 GHz to destroy or debilitate vegetation. U.S. Patent No. 3,499,437 issued to Balamuth on March 10, 1970 discloses use of pulsed ultrasonic energy for cell heating. U.S. Patent No. 4,758,318 issued to Yoshida on July 19, 1988 discloses use of a pulsating direct current to kill molds in soil. U.S. Patent No. 5,060,414 issued to Wayland on October 29, 1991 discloses pretreatment of soil with radio-frequency (RF) electromagnetic fields followed by microwave exposure for control of vegetation, fungi, nematodes, insects, etc.

Commercial nurseries often kill pests and pathogens in potting soils and other growing media by injecting steam into the material and heating the material to approximately 1000C for >30 minutes. This long and intense heating is necessary because steam tends to rise and "vent" out of the soil, and does not typically move through and penetrate a soil mass uniformly. Higher temperatures and prolonged times are a means of compensating for this inefficiency. However, the "overheating" of soil is not desirable because it also kills many beneficial microbes and may change the soil chemistry of nutrient ions. Also, because heating soil by means of steam is relatively expensive due to the cost of generating steam and the relative inefficiency of heat transfer to soil, nurseries that use large volumes of soil typically employ methyl bromide fumigants to disinfect growing media.

Grape phylloxera (Daktulosphaira vi tifol iae) is arguably the most significant threat to European grapes

( Vi tis vinifera L) throughout the world. Control of phylloxera can be achieved predictably by use of only a few methods. The most universal method is the use of resistant rootstock technology. Wild American species of grapes, having evolved in the presence of phylloxera, tend to be the most resistant. By using selections or hybrids of these wild grape species as rootstocks, viticulturists can graft onto them cultivars of commercial utility. This technology has ameliorated the phylloxera problem for more than 100 years but needs continuous updating and refining. Also, phylloxera can overcome some resistant rootstocks . Because of these problems, new rootstocks must be developed continuously and/or therapeutic methods must be used. The only currently available therapeutic methods, however, are use of insecticides. Use of insecticides is not predictably efficacious however because (i) phylloxera live deeply in the soil and it is difficult for chemicals to penetrate the heavy clay soils that the insects prefer; (ii) phylloxera populations grow extremely rapidly and can rebound rapidly; and (iii) decimation of phylloxera populations does not readily result in reversal of vine damage. Therefore, there is a need for other therapeutic methods . While application of thermal energy is a well-known method for managing plant pests and pathogens in a variety of soils and plant materials, its utility as a soil or potting medium treatment method has not been justified economically or accepted by agriculturists. Further, many of the prior methods of treatment require considerable energy consumption and are not capable of targeting specific organisms. Therefore, there is a further need for a method of efficiently and effectively applying thermal energy to organisms for their destruction.

The foregoing patents reflect art of which the applicant is aware and are tendered with the view toward discharging applicant's acknowledged duty of candor in disclosing information which may be pertinent in the examination of this application. It is respectfully stipulated, however, that none of these patents teach or render obvious, singly or when considered in combination, applicant's claimed invention.

SUMMARY OF THE INVENTION The present invention generally pertains to a method of treating pests, pathogens and other undesirable organisms found in soil and other growing media such as soil substitutes, additives and solutions, with electromagnetic energy wherein the undesired organisms are selectively heated and destroyed.

By way of example, and not of limitation, the method of the present invention comprises the steps of exposing a growing media such as soil containing undesirable organisms to a plurality of high frequency electromagnetic energy pulses. Preferably, the wavelength is chosen such that the electromagnetic energy excites molecules in the undesired organism (e.g. , matches a resonant frequency of the organism) but does not excite water or other molecules in the surrounding soil or tissue mass. The heat thus induced in the undesired organisms dissipates sufficiently slowly that metabolic activity in the organisms is altered and the organisms are selectively reduced or destroyed.

Treatment of agricultural soils and other growing media in accordance with the method of the present invention can be used to eliminate or reduce populations of (i) insect pests such as phylloxera, cutworms, beetles, ants, and root aphidε, (ii) invertebrate pests such as sowbugs, centipedes, millipedes, mites and slugs, (iii) nematode pests such as root knot nematodes, dagger nematodes, and lesion nematodes, (iv) weed seeds, (v) plant pathogenic bacterial such as crown gall and soft rot, (vi) plant pathogenic fungi in soils (e.g., Pytophthora , Fusarium, Rhizoctonia) , crop debris (e.g., Scl erotium oryzae) or in dead tree roots (e.g., Armillaria) . Further, the present invention can be used to replace or minimize (i) soil fumigants, (ii) insecticides, (iii) herbicides and (v) nematicides, and (vi) crop plowing and burning.

An object of the invention is to treat organisms with short pulses of electromagnetic energy.

Another object of the invention is to generate thermal energy and selectively apply the thermal energy to materials for disinfestation purposes.

Another object of the invention is to effectively apply thermal energy to materials to eliminate or reduce populations of pests and/or pathogens.

Another object of the invention is to selectively heat targeted chemicals and/or organisms through resonance .

Another object of the invention is to selectively heat targeted chemicals and/or organisms with radio¬ frequency energy with minimal harm to desirable organisms .

Another object of the invention is to minimize or eliminate the use of agricultural pesticides to control soil or media borne pests and/or pathogens .

Another object of the invention is to provide for in situ elimination of pests and/or pathogens in materials using thermal energy.

Another object of the invention is to selectively kill or retard growth of pest and/or pathogen organisms over beneficial organisms. Another object of the invention is to promote, trigger or synergistically interact with natural processes that inhibit pests and/or pathogens . Another object of the invention is to reduce human- pathogenic fungi .

Further objects and advantages of the invention will be brought out in the following portions of the specification, wherein the detailed description is for the purpose of fully disclosing preferred embodiments of the invention without placing limitations thereon. BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood by reference to the following drawings which are for illustrative purposes only:

FIG. 1 is a graph showing the eclosion of grape phylloxera eggs at 370C as a function of incubation time.

FIG. 2 is a graph showing the eclosion of grape phylloxera eggs at 400C as a function of incubation time.

FIG. 3 is a graph showing the eclosion of grape phylloxera eggs at 430C as a function of incubation time.

FIG. 4 is a graph showing the percent survival of

Fusarium oxysporium f . sp . dian thi in soils held at selected constant temperatures as a function of time.

FIG. 5 is a graph showing the survival of Phytophthora capsi ci and P . ci troph thora zoospores as a function of time exposures to continuous ultraviolet light emission. FIG. 6 is a graph showing the survival of Phytophthora ci trophthora zoospores as a function of energy levels from an ultraviolet laser.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The interaction between electromagnetic energy and matter depends on the physical properties of the source, as well as the chemical composition of the sample. The thermodynamics and kinetics of the thermally induced chemical reactions taking place in a heated sample depending primarily on the chemical composition of the sample and many physical factors. The amount of absorption of radiant energy of a target sample is a function of both the molecular structure of the same and the physical properties of the radiation such as wavelength. Thus, matching the energy source with the target sample allows specific types of molecules to be electronically excited and irreversible chemical effects can be obtained, including reactions that affect biological functions such as cell division.

In U.S. Patent No. 5,364,645, which is incorporated herein by reference, it was shown that treatment of a food object with pulsed ultraviolet lasers causes non- reparable damage to nucleic based structures in microorganisms present on that object without altering the surface properties of the food object. Pulses having a duration ranging from approximately 1 ns to 100ns, preferably 20 to 30ns, and energy densities ranging from approximately .001 to 2 J/cm² were shown to be effective for this purpose.

Pulsed energy delivers higher instantaneous power levels with lower overall energy requirements than with continuous heating and, therefore, is more efficient. Further, use of a pulsed high power source provides for higher temperature heating in a shorter period of time.

Thus, at power levels where continuous wave heating would result in atomization of exposed molecules, pulsed treatment will result in heat transfer without atomization. For pulse outputs in the range of 1 to 2

J/cm² per pulse, the average power levels can be as a high as a few MW/cm². Treatment by exposure to a plurality of pulses effects a near instantaneous increase in the concentration of thermally excited molecules, while heat dissipation is still sufficient slow to be destructive to the targeted organisms .

In accordance with the present invention, an electromagnetic energy source such as a radio transmitter is tuned or synchronized with a targeted molecular structure so that heat transfer takes place between the source and the sample. The wavelength is selected such that treatment of the target sample excites particular molecular structures in the sample, such as lipids, but will either not excite water molecules or other molecular structures in adjacent plant growth or will not excite them to a level which will cause molecular damage. In other words, the frequency of the transmitter is matched to the resonant frequency of the molecular structure of the targeted sample. It is also preferable to keep the bandwidth of the signal as narrow as practicable so that molecular structures which resonate at adjacent frequencies will not be excited As a result, energy transfer to the targeted sample is maximized without causing harm to adjacent plant growth. Additionally, particular undesirable organisms can be targeted m this manner without affecting other desirable organisms While heating energy can be applied to soil using resistive, capacitive or inductive coupling, or by treatment with microwaves, lasers and the like, the most effective and preferred source is electromagnetic energy in the radio-frequency spectrum As explained above, the particular frequency is selected to cause excitation, or resonance, of the molecular structure to be targeted. Since a transmitted signal can also generate harmonic frequencies, and the excitation frequency could be at one of those harmonics, the frequency selected can also be a function of the depth of soil penetration required as well as the chemical composition of the organisms to be destroyed. For example, frequencies m the spectrum of approximately 100 MHz will penetrate the so l to depths of approximately 15 feet while, at the same time, be destructive to many pests or pathogens without harming adiacent plant material.

When treating pests and pathogens in the soil and other growing media, their exact location may not be known. Accordingly, the beam width of the treatment source should be sufficiently wide so as to cover all possible sites of infestation. Alternatively, a more narrow beam width could be used and the area sweeped with the beam. Since the wavelength is selected to cause excitation of only targeted molecular structures m the undesired organisms, use of wide beam widths or sweeping is possible without harming plant growth. It will also be appreciated that, where the location of infestations are known, the infestation site can be targeted by using a highly directional antenna with a very narrow beam width.

Example 1 The eclosion of grape phylloxera eggs was tested as a function of temperature and heating time. It was found that efficient control of the eclosion process was possible with temperatures as low as 370C as shown m FIG. 1 The effects at 400C and 430C were also demonstrated efficiency as shown m FIG. 2 and FIG. 3, respectively, and suggested that rapid heating would provide other effective heating profiles to accomplish the required control .

Example 2 The survival of Fusarium oxyspori um f . sp . dian thi m soils held at constant temperatures is shown m FIG 4, for the selected temperatures of 500C, 550C, 650, and 700C Soil containing amounts of inoculum were placed m constan -temperature incubators for various lengths of time. At the end of the exposure period, soils were assayed for viable propagules. Survival is expressed as a percentage of propagules that survived the heat exposure treatment. The relationship between temperature and control shows that, at 500C, complete control (i.e., zero percent survival) can be achieved in less than two hours. As temperatures increase, survival times are greatly reduced.

Example 3 The effects of pulsed ultraviolet treatment and continuous ultraviolet treatment on pathogens in irrigation water were compared. FIG. 5 compares the survival rates of Phytophthora capsici and P . ci trophthora zoospores to exposure to continuous ultraviolet light emission m terms of the number of viable propagules per 100 ml as a function of exposure time. The spores were suspended m distilled water. The points on the graph represent the mean of five replications. Vertical bars indicate ±1 S.D. The greater survival of P. capsici after five seconds of exposure is significant (P=0.05) . FIG. 6 shows the survival rate of Phytoph thora ci trophthora zoospores to exposure to an ultraviolet laser in terms of the percent of viable spores remaining as a function of energy levels. Spores were suspended in distilled water and were pumped through a quartz- indowed treatment cell for exposure to UV radiation. Beam intensity and water flow rate were adjusted to provide different ultraviolet exposure doses. Each point on the graph represents the mean of five replications. Comparison of FIG. 5 and FIG. 6 demonstrates that pulsed ultraviolet treatment is several orders of magnitude more efficient than continuous ultraviolet treatment to control fungi and bacteria in water used for irrigation.

Example 4 The advantages and the treatment efficacy of pulsed power in comparison to continuous power can be seen m U.S. Patent No. 5,364,645 where pulsed ultraviolet treatment is shown to be more efficient than continuous ultraviolet treatment for the control of surface micro¬ organisms in foods and in other materials. Since it is known that an object can be heated using electromagnetic energy in the radio-frequency spectrum and, further, since it is known that radio-frequency energy can penetrate soil, water and other objects, using the same principle of treating pests and pathogens on the surface of food using a pulsed ultraviolet energy source, pests and pathogens in growing media such as soil can be controlled by treatment of the soil using pulsed electromagnetic energy. The pests and pathogens will be reduced or eliminated by heating, without damage occurring to the plants. Further, pulsed energy applied at selective frequencies will cause destruction of certain undesirable pests and pathogens without harming desirable organisms.

Accordingly, it can be seen that the present invention provides for the efficient and effective control of pests and pathogens in soil and other growing media through the pulsed treatment of the growing media with electromagnetic energy emitted at a wavelength which penetrates the growing media and causes excitation of targeted molecular structures sufficient to heat and destroy those structures without causing harm to molecular structures in adjacent plant growth. Although the description above contains many specificities, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments of this invention. Thus the scope of this invention should be determined by the appended claims and their legal equivalents.

Claims

CLAIMSWhat is claimed is:

1. A method of controlling undesired organisms m a plant growing media, comprising the steps of exposing plant growing media containing undesirable organisms to a plurality of electromagnetic energy pulses wherein said organisms are reduced or eliminated by selectively heating the organisms without harming adjacent plant growth.

2. A method as recited in claim 1, further comprising the step of penetrating said growing media with said energy pulses.

3. A method as recited in claim 1, further comprising the step of generating said electromagnetic energy pulses at the approximate resonant frequency of molecular structures in the undesired organisms.

4. A method of controlling undesired organisms in plant growing media, comprising the steps of treating plant growing media containing undesirable organisms with a plurality of electromagnetic energy pulses at the approximate resonant frequency of the undesired organisms wherein the organisms are reduced or eliminated by exciting molecular structures in the undesirable organism without harming desirable molecular structures, and wherein heat induced in the undesired organisms dissipates sufficiently slowly that the organisms are reduced or eliminated by thermal energy deposition.

5. A method as recited in claim 4, further comprising the step of penetrating said growing media with said energy pulses.

6. A method of controlling undesired organisms in plant growing media, comprising the steps of treating plant growing media containing undesirable organisms with a plurality of electromagnetic energy pulses at the approximate resonant frequency of the undesired organisms wherein said energy pulses penetrate said growing media, wherein said undesirable organisms are reduced or eliminated by selectively heating the organisms through excitation of selected molecular structures in the organisms without harming desirable molecular structures, and wherein heat induced in the undesired organisms dissipates sufficiently slowly that the organisms are reduced or eliminated by thermal energy deposition.