GB2059772A - Pesticidal compositions - Google Patents

Abstract

The invention relates to pesticidal compositions. There are provided pesticidal compositions comprising (a) the compound of formula <IMAGE> and (b) a pyrethroid insecticide having the general formula <IMAGE> wherein A is an optionally-substituted aralkyl, alkyl, cycloalkyl or arylaminoalkyl group, R is hydrogen, cyano or ethynyl, X is alkyl, alkenyl, aralkyl or aryloxy and n is 1 to 5, their preparation, and their use in combating pests. Compositions according to the invention exhibit enhanced pesticidal activity against ticks such as Boophilus microplus, the single-host cattle tick, and against insects such as Plutella xylostella, the diamond black moth.

Description

SPECIFICATION Pesticidal compositions This invention relates to pesticidal compositions, their preparation and their use.

Dimethyl 2 - chloro -1 - (2,4 - dichlorophenyl) vinyl phosphate, i.e. the compound of formula

commonly referred to as "dimethylvinphos", is described, together with its use as an insecticide, in UK Patent Specification No. 1,011,022.

A class of insecticides commonly referred to in the art as "pyrethroid insecticides" is also known and various examples of pyrethroid insecticides are described, together with their preparation, in UK Patent Specification Nos. 1,413,491 and 1,553,153, and in US Patents Nos. 3,835,178 and 3,996,244.

It has now been discovered that mixtures of dimethylvinphos and certain pyrethroid insecticides exhibit surprising enhanced activity against ticks such as Boophilus microplus, the single-host cattle tick and against insects such asPlutellaxylostella, the diamond back moth.

The present invention provides a pesticidal composition comprising (a) dimethylvinphos, i.e. the compound of formula I above, and (b) a pyrethroid insecticide having the general formula

wherein A is an optionally-substituted aralkyl, alkyl, cycloalkyl or arylaminoalkyl group, R is hydrogen, cyano or ethynyl, X is alkyl, alkenyl, aralkyl or aryloxyandn is 1 to 5.

An alkyl, cycloalkyl or alkenyl group represented by A or X preferably contains up to 6 carbon atoms, and an aralkyl, arylamino-alkyl or aryloxy group represented by A or X preferably contains up to 12 carbon atoms.

It should be understood that the compound of the general formula II may be present in the form of any one of its optical or geometric, for example cis-trans, isomers, or in the form of a mixture of isomers, for example a racemate. A mixture of two or more compounds according to the general formula II may be present When A represents an optionally-substituted cycloalkyl group, it preferably represents a cyclopropyl group of general formula:

wherein Ra and Rb both represent an alkyl group hav ing from 1 to 6 carbon atoms, especially a methyl group, or a halogen atom, especially a chlorine, bromine or fluorine atom; or Ra and Rb together represent an alkylene group having from 2 to 6, especially 3, carbon atoms; or Ra represents a hydrogen atom and Rb represents an alkenyl group having from 2 to 6 carbon atoms, especially an isobutenyl group, a haloalkenyl group having from 2 to 6 carbon atoms and from 1 to 3 chlorine and/or bromine atoms, especially a monochlorovinyl, monobromovinyl, dichlorovinyl or dibromovinyl group or a haloalkyl group having from 2 to 6 carbon atoms and from 2 to 5 chlorine and/or bromine atoms, especially a tetrachloroethyl, tetrabromoethyl or dibromodichloroethyl group; or Ra and Rb together with the interiacent carbon atom represent an unsaturated carbocyclic ring system, of upto 12 carbon atoms especially an indenylidene group;Rc and Rd both represent an alkyl group having 1 to 6 carbon atoms, especially a methyl group; or Rc and Rd together represent an alkylene group having from 2 to 6, especially 3, carbon atoms. Preferably Ra and Rb both represent a methyl group or a chlorine atom, or Ra and Rb together represent an alkylene group containing 3 carbon atoms, or Ra represents a hydrogen atom and Rb represents an isobutenyl group, a monochlorovinyl, monobromovinyl, dichlorovinyl or dibromovinyl group or a tetrachloroethyl, tetrabromoethyl or dibromodichloroethyl group, or Ra and Rb together with the interjacent carbon atoms represent an indenylidene group; and Rc and Rd both represent methyl groups or R0 and Rd together represent an alkylene group containing 3 carbon atoms.

When A in the general formula II represents an optionally-substituted aralkyl group, it preferably represents a substituted benzyl group of the general formula:

wherein Z represents a halogen, preferably chlorine, atom, or an alkoxy or haloalkoxy group of 1 to 4 carbon atoms, for example a methoxy or dif luorometboxy group, and Q represents an alkyl group of 1 to 6 carbon atoms, especially a branched chain group, for example an isopropyl group. Preferably the group Z is in the 4-position on the benzene ring.

When A represents an optionally-substituted arylaminoalkyl group, it preferably represents a substituted anilinomethyl group of general formula: Certain of the chemical formula(e) appearing in the printed specification were submitted after the date of filing, the formula(e) originally submitted being incapable of being satisfactorily reproduced.

wherein Y' and Y2 each independently represents a halogen, preferably chlorine, atom, or an alkyl or haloalkyl group of 1 to 4 carbon atoms, for example a trifluoromethyl group, and Q' represents an alkyl group of 1 to 6 carbon atoms, especially a branched chain group, for example an isopropyl group. Preferably Y' is a chlorine atom in the 2-position on the benzene ring andY2 is a trifluoromethyl group in the 4-position on the benzene ring.

Preferablyn represents 1 and X represents a phenoxy or a benzyl group, especially a 3 - phenoxy or3 - benzyl group.

The most preferred pyrethroid insecticides for use in the pesticidal composition according to the invention have the general formula I wherein A is alpha isopropyl - 4 - chlorobenzyl, 2,2,3,3 tetramethylcyclopropyl, 2- (2,2- dichlorovinyl) - 3,3- dimethylcyclopropyl, 2 - (2,2 - dibromovinyl) - 3,3 - dimethylcyclopropyl or 3,3 - dimethylspiro (cyclopropane - 2,2 indene)yl; R is hydrogen or cyano; and n is 1 and X is 3 - phenoxy. Especially preferred are the compounds known as cypermethrin, fenvalerate, cipothrin and decamethrin whose formulae are given in the Examples herein.

The weight ratio of the pyrethroid insecticide to dimethylvinphos is preferably in the range 6:1 to 1:60, more preferably in the range 3:1 to 1:40.

The mixture of dimethylvinphos and the pyrethroid insecticides produces a surprising enhanced effect, for example with respect to ticks such as Boophilus micro plus, the single-host cattle tick, and to insects such asPlutellaxylostella,the diamond back moth. The invention therefore also provides a method of combating pests at a locus which comprises applying to that locus a pesticidal composition according to the invention.

The pesticidal composition according to the invention preferably also comprises a carrier, especially at least two carriers, at least one of which is a surfaceactive agent The invention also provides a process for preparing a pesticidal composition which comprises bringing a compound of formula I and a pyrethroid insecticide of formula II into association with at least one carriertherefor.

A carrier in a composition according to the invention is any material with which the active ingredient is formulated to facilitate application to the locus to be treated, which may for example be a plant, seed or soil, orto facilitate storage, transport or handling.

A carrier may be a solid ora liquid, including a material which is normally gaseous but which has been compressed to form a liquid, and any of the carriers normally used in formulating pesticidal compositions may be used.

Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for example talcs; magnesium aluminium silicates, for example attapulgites and vermiculites; aluminium silicates, for example kaolinites, montmorillonites and micas; calcium carbonate; calcium sulphate; synthetic hydrated silicon oxides and synthetic calcium or aluminium silicates; elements, for example carbon and sulphur; natural and synthetic resins, for example coumarone resins, polyvinyl chloride, and styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes, for example beeswax, paraffin wax, and chlorinated mineral waxes; and solid fertilisers, for example super-phosphates.

Suitable liquid carriers include water; alcohols, for example isopropanol and glycols; ketones, for example acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic oraraliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosine and light mineral oils; chlorinated hydrocarbons, for example carbon tetrachloride, perchloroethylene and trichloroethane. Mixtures of different liquids are often suitable.

Pesticidal compositions are often formulated and transported in a concentrated form which is subsequently diluted by the user before application. The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be non-ionic or ionic. Examples of suitable surfaceactive agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation products of fatty acids or aliphatic amines or am ides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitan, sucrose or pentaerythritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example p - octylphenol orp - octylcresol, with ethylene oxide and/or propylene oxide; sulphates or sulphonates ofthese condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric orsulphonic acid esters containing at least 10 carbon atoms in the molecule, for example sodium lauryl sulphate, sodium secondary alkyl sulphates, sodium salts of sulphonated castor oil, and sodium alkylaryl sulphonates such as sodium dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions of the invention may for example be formulated as wettable powders, dusts, granules, solutions, emulsifiable concentrates, emulsions, suspension concentrates and aerosols.

Wettable powders usually contain 25, 50 and 75% w of active ingredient and usually contain, in addition to solid inert carrier, 3-10% w of a dispersing agent and, where necessary, 0-10% w of stabiliser(s) and/or other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similar composition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usu ally containing 2-10% w of active ingredient Granules are usually prepared to have a size between 10 and 100 BS mesh (1.676-0.152 mm), and may be manufactured by agglomeration or impregnation techniques.Generally, granules will contain 2-25% w active ingredient and 0-10% w of additives such as stabilisers, slow release modifiers and binding agents. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 1 0-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-20% w/v of other additives such as stabilisers, penetrants and corrosion inhibitors.Suspension concentrates are usually compounded so as to obtain a stable, non-sedimenting flowable product and usually contain 10-75% w active ingredient, 0.5-15% w of dispersing agents, 0.1-10% w of suspending agents such as protective colloids and thixotropic agents, 0-10% w of other additives such as defoamers, corrosion inhibitors, stabilisers, penetrants and stickers, and water or an organic liquid in which the active ingredient is substantially insoluble; certain organic solids or inorganic salts may be present dissolved in the formulation to assist in preventing sedimentation or as antifreeze agents for water.

Aqueous dispersions and emulsions, for example compositions obtained by diluting a wettable powder or a concentrate according to the invention with water, also lie within the scope of the present invention. The said emulsions may be of the water-in-oil orofthe oil-in-watertype, and may have athick 'mayonnaise'-like consistency.

The compositions of the invention may also contain other ingredients, for example, other compounds possessing pesticidal, herbicidal or fungicidal properties or attractants, for example pheromones or food ingredients, for use in baits and trap formulations.

The following examples illustrate the invention.

Examples 1 to 3 Activity of pyrethroididimethylvinphos mixtures against Boophilus microplus (Single-host cattle tick) The coefficients of co-toxicity of cypermethrin, fenvalerate and cipothrin with dimethylvinphos were assessed by the following method.

The single-host cattle tick used in these examples was an OP-resistant strain, the Mount Alford strain of Boophilus micro plus.

A 0.1% by weight solution of the active ingredient to be tested was prepared in acetone containing 10% by weight of polyethylene glycol. Varying concentrations were obtained by diluting this solution. 1 ml of test solution was applied evenly to an 11 cm filter paper inside a petri dish. When sufficiently dry, the filter paper was folded in half and crimped along part of its outer edge to form a packet. About 80-100 two to three week old one-host cattle tick larvae (Boophilus microplus) were transferred into the packet, which was then completely sealed. The packet was then placed in an incubator at 27 C and 80% relative humidity. After 24 hours the packet was opened and the percentage of dead and moribund larvae was assessed.

Toxicity indices were then calculated using the following equation:- Toxicity Index(T.I.)= LC 50 of ethyl parathion (standard) The joint action of the two active components of a mixture was analysed by the method of Yun-Pei Sun and E. R. Johnson, Journal of Economic Entomology, 1960, Volume 53, No. 5, pages 887-892.

Thus, the joint action of two pesticides were analysed by determining the actual toxicity indices of the components and of mixtures of the compounds by reference to dosage-mortality curves. The theoretical toxicity of the mixture is equal to the sum of toxicity indices calculated from the percentage of each component multiplied by its respective toxicity index. Therefore, the joint toxicity or Co-toxicity coefficientof a mixture Actual toxicity index of a mixture Theoretical toxicity index of a mixture x100 A coefficient of a mixture near 100 indicates proba bilityofsimilaraction by the two pesticides; independent action usually should give a coefficient less than 100, while a coefficient significantly above 100 strongly indicates synergism.

Cypermethrin, the pyrethroid insecticide used in Example 1, has the formula:

Fenvalerate, the pyrethroid insecticide used in Example 2, hastheformula:

Cipothrin, the pyrethroid insecticide used in Example3, hastheformula:

The results of Examples 1 to 3 are given in Tables I to lll following: Table I

Compound or Weight Ratio LCso Coefficient Compound Mixture of Mixture % wt of solution ofCo-toxicity cypermethrin 0.0025 dimethylvinphos 0.010 cypermethrinl dimethylvinphos 1:1 0.0016 247 cypermethrinl dimethylvinphos 1::3 0.0012 476 cypermethrinl dimethylvinphos 1:6 0.0023 306 ethyl parathion 0.0081 Table

Compound or Weight Ratio LC50 Coefficient Compound Mixture of Mixture /O wt ofsolution of Co-toxicity fenvalerate 0.0022 dimethylvin phos 0.010 fenvaleratel dimethylvinphos 1:1 0.0022 171 fenvaleratel dimethylvinphos 1:3 0.0023 228 fenvaleratel methylvinphos 1::6 0.0040 191 ethyl parathion 0.0081 Table 111

Compound or Weight Ratio LCso%Wt Coefficient Compound Mixture of mixture of solution of Co-toxicity cipothrin 0.0067 dimethylvinphos 0.0070 cipothrinl dimethylvinphos 1:1 0.0033 219 cipothrinl dimethylvinphos 1:3 0.0032 230 cipothrinl dimethylvinphos 1:6 0.0028 261 ethyl parathion 0.0036 The coefficients of co-toxicity in Tables I to Ill clearly indicate synergism in the mixtures tested.

Example 4 Activity ofcypermethrinldimethylvinphos mixtures against Plutella xylostella (diamond back moth) Activity of cypermethrin/dimethylvinphos mixtures against vegetable pests was determined in tests involvingPlutellaxylostella (diamond back moth) by the following method.

Aqueous dispersions of dimethylvinphos, of cypermethrin and of mixtures thereof were prepared from commercial 50% w/w wettable powder formulation of dimethylvinphos and 15% w/v emulsifiable concentrate formulation of cypermethrin.

3 to 4 instar larvae of Plutella xylostella were treated by momentarily dipping individual larvae in the various aqueous dispersions. 15 to 20 larvae were used for each dispersion and percentage mortalities were assessed at 6 hours and 24 hours after dipping.

Results of these tests are given in Table IV following: Table IV

Mortality of Concentration Concentration Plutella xylostella(%) Aqueous f of dimethylvinphos { of cypermethrin dispersion (% w/v) (% w/v) 6 hours 24 hours i 0.03 - 0 0 ii | 0.05 1 I 0 iii 0.07 - 0 0 iv 0.1 - 0 0 v - 0.003 33 33 vi 0.03 0.003 75 75 vii 0.05 0.003 82 86 viii 0.07 0.003 95 95 ix 0.1 0.003 95 100 The results shown in Table IV clearly indicate a joint action of dimethylvinphos/cypermethrin which is significantly greater than the additive effect of the individual components against Plutella xylostella, at the concentrations tested.

Example 5 Activity of decamethrinidimethylvinphos mixtures against Boophilus micro plus (Single-host cattle tick) Decamethrin, the pyrethroid insecticide used in this Example has the formula:

(lRc,s - S - isomer) The coefficients of co-toxicity of decamethrin with dimethylvinphos were assessed against adult single-host cattle ticks of the susceptible, Yeerong pilly, strain of Boophilus microplus by the following procedure.

A 5% by weight solution of the active ingredient to be tested was prepared in acetone. Varying concent rations were obtained by diluting this solution.

Fully engorged female ticks were placed ventral side uppermost in a petri dish. Each test solution was taken up in a micrometer syringe and a 2 microlitre droplet of solution was applied to the ventral abdomen of each tick. Ten ticks were treated with each solution. Treated ticks were stored for 14 days in an incubator maintained at 27 C and 80% relative humidity. The reduction in the amount of eggs produced during this period was assessed. Four concentrations of each active ingredient were applied to obtain a dosage response curve and the test was repeated two or three times. From these dosage response curves were calculated ED50 figures, being the effective dose to produce a 50% reduction in the egg mass layed by the ticks.

Toxicity indices were then calculated using the following equation:- Toxicity Index (T.I.) = ED50 of ethyl parathion (standard) ED50 of test compound The joint action of the two active components was analysed by the method of Yun-Peisun and E. R.

Johnson discussed above in relation to Examples 1 to3.

The results of these tests are given in Table V following: TABLE V

Compound or Weight Ratio ED50 Coefficient Compound Mixture of Mixture gltick of Co-toxicity decamethrin 0.13 dimethylvinphos 5.5 decamethrin/ dimethylvinphos 1:1 0.077 331 decamethrin// dimethylvinphos 1:3 0.13 378 decamethrin/ dimethylvinphos 1:6 0.18 442 ethyl parathion 2.3 The coefficients of co-toxicity in Table V clearly indicate synergism in the mixtures tested.

Claims (15)

1. A pesticidal composition comprising (a) the compound of formula

and (b) a pyrethroid insecticide having the general formula

wherein A is an optionally-substituted aralkyl, alkyl, cycloalkyl orarylaminoalkyl group, R is hydrogen, cyano or ethynyl, X is alkyl, alkenyl, aralkyl or aryloxy and n is 1 to 5.

2. A composition according to Claim 1 wherein A in the compound of formula II represents a cyclopropyl group of formula

wherein Ra and Rb both represent a methyl group or a chlorine atom, or Ra and Rb together represent an alkylene group containing 3 carbon atoms, or Ra represents a hydrogen atom and Rb represents an isobutenyl group, a monochlorovinyl, monobromovinyl, dichlorovinyl or dibromovinyl group or tetrachloroethyl, tetrabromoethyl or dibromodichloroethyl group, or Ra and Rb together with the inter jacentcarbon atom represent an indenylidene group and Rc and Rd both represent methyl groups or Rc and Rd together represent an alkylene group containing 3 carbon atoms.

3. A composition according to Claim 1 wherein A in the compound of formula II represents a group of formula

wherein Z represents a halogen atom or an alkoxy group of 1 to 4 carbon atoms and Q is a branchedchain alkyl group of 3 to 6 carbon atoms.

4. A composition according to any one of Claims 1 to 3 wherein in the compound of formula Il n is 1 and Xis a 3 - phenoxy group.

5. A composition according to Claim 1 wherein A in the compound of formula II is alpha - isopropyl -4 - chlorobenzyl, 2,2,3,3 tetramethylcyclopropyl, 2 (2,2 - dichlorovinyl) - 3,3 - dimethylcyclopropyl, 2 - (2,2 - dibromovinyl) - 3,3 - dimethylcyclopropyl or 3,3 - dimethylspiro (cyclopropane - 2,2 - indene)yl; R is cyano; n is 1 and X is 3 - phenoxy.

6. A composition according to Claim 5 wherein the compound offormula II is cypermethrin.

7. Acomposition according to Claim Swherein the compound of formula II is fenvalerate.

8. A composition according to Claim 5 wherein the compound of formula Il is cipothrin.

9. A composition according to Claim 5 wherein the compound of formula II is decamethrin.

10. A composition according to any one of Claims 1 to 9 wherein the pyrethroid insecticide and the compound of formula I are present in the composition in relative amounts by weight in the range 6:1 to 1:60.

11. A composition according to Claim 10 wherein the relative amounts by weight are in the range 3:1 to 1:40.

12. A composition according to Claim 1 substantially as hereinbefore described with particular reference to any one of Examples 1 to 5.

13. A process for preparing a pesticidal composition according to any one of Claims 1 to 12 which comprises bringing a compound of formula I as defined in Claim 1 and a pyrethroid insecticide of formula II as defined in Claim 1 into association with at least one carriertherefor.

14. Aprocess according to Claim 11 substantially as hereinbefore described with particular reference to any one of Examples 1 to 5.

15. A method of combating pests at a locus which comprises applying to the locus a pesticidal composition according to any one of Claims 1 to 12.