GB2187385A - Method of combatting colorado beetles using chemical compounds and compositions containing the chemical compounds - Google Patents

Abstract

A method for combatting colorado beetles at a locus, which comprises applying the locus a compound of formula: <IMAGE> wherein R<1> represents a halogen atom or a methyl group; R<2> represents a halogen atom, a methyl or trifluoromethyl group; and X represents a hydrogen atom or a fluorine atom; in the form of a trans enantiomer pair consisting of either the [1R trans]S and [1S trans]R or the [1R trans]R and [1S trans]S isomers; and pesticidal compositions containing the trans enantiomer pairs.

Description

SPECIFICATION Method of combatting colorado beetles using che mical compounds and compositions containing the chemical compounds The present invention relates to a method for combatting colorado beetles using chemical com- pounds and to compositions containing the chemical compounds.

The a:-cyanophenoxybenzyl-3-vi nylcyclopro panecarboxylate pyrethroid insecticides such as cypermeth rin are widely used to control insect pests.

There is, however, a continuing need in specific outlets forcompoundswhich discriminate between insect pests and beneficial insects such as predators.

oc-Cyanophenoxybenzyl-3-vinylcyclopropanecarboxylate molecules contain three centres of asymmetry and may therefore exist in eight isomeric forms. It is well known that isomers having the vinyl and carboxy substituents in a cis configuration about the cyclopropane ring, especially the [IR cisiS isomer, are the most active, (Synthetic Pyreth roids, ACS Symposium Series 42). This is evidenced by the commercial success of products consisting of the [1 R cis]S isomer, such as deltamethrin, orthose enriched in the [1 R cis]S isomer such as cypermethrin or cyhalothrin in the form ofthe enantiomer pair consisting ofthe [1 R cisiSand [15 cis]R isomers.

We have not found that a-cyanophenoxybenzyl-3vinylcyclopropaneca rboxylate pyreth roid insecticides intheform oftransenantiomerpairs are particularly active againstcolorado beetles.

Accordingly the present invention provides a method for combatting colorado beetles at a locus, which comprises applying to the locus an effective amount of a compound offormula:

wherein R1 represents a halogen atom or a methyl group; R2 represents a halogen atom or a methyl or a trifluoromethyl group; and X represents a hydrogen atom or a fluorine atom; in the form of a trans enantiomer pairconsisting of either the [1 R trans]S and [1 trans orthe [IR trans]R and [1 S trans isomers.

Where R1 and/or R2 represents a halogen atom it may be,forexample,achlorineorbromine atom.

When X represents a hydrogen atom, R1 and R2 preferably both represent a chlorine or bromine atom or a methyl group, or R1 represents a chlorine atom and R2 represents a trifluoromethyl group. When X represents a fluorine atom, R1 and R2 both preferably representa chlorine atom.

Aparticularly preferred compound of formula (I) is cypermethrin which has the chemical name (RS) -cyano-3-phenoxybenzyl-(1 RS)-cis-trans-3-(2,2-dich- lorovinyl)-1 ,1 -dimethylcyclopropanecarboxylate.

In the method according to the invention, preferably at least 80%, more preferably 90%, e.g. 95% of the compound offormula (I) is in the form of an enantiomer pair consisting of either the [1 R transits and [iStrans]R orthe [1 Rtrans]R and the [iStrans]S isomer.

Itis well known that compounds offormula (I) in the cis form are generally more active against insects than thos in the corresponding trans form. For example, the mixture of four isomers in the trans formofcypermethrin is an order of magnitude less active against colorado beetles than the corresponding mixture offour cis isomers.

Surprisinglywe have now found in tests that the enantiomer pairs in thetransform of a compound of formula (I) exhibit useful activity against colorado beetles (Leptinotarsa decemlineata). Thus the enantiomer pairs are highly selective between colorado beetles and beneficial insects, in particular ladybirds (Coccinella septempunctata) and ca ra bids (Agonum dorsale). This selectivity is notfound in the corresponding racemic compound offormula (I) nor in the two mixtures offourisomers.

Colorado beetles feed principally on potato plants.

The invention therefore includes a method as defined above in which the locus is a potato plant.

The method according to the invention preferably comprises the application of compositions comprising a compound offormula (I) in the form of a trans enantiomer pair and a carrier. Therefore, according to another aspect of the invention,there is provided a pesticidal composition comprising a compound of formula (I) in the form of a trans enantiometer pair as defined previouslytogetherwith a carrier.

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 betreated, which may for example be a plant, seed or soil, orto facilitate storage, transport or handling. A carrier may be a solid or a 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. Preferably compositions according to the invention contain 0.5 to 95% by weight of active ingredient.

Suitable solid carriers include natural and synthetic clays and silicates, for example natural silicas such as diatomaceous earths; magnesium silicates, for ex- ampletalcs; magnesium aluminium silicates, for exampleattapulgitesandvermiculites; aluminium silicates, for example kaolinites, montmorillonites and micas; calcium carbonate; calcium sulphate; ammonium 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, polyvinlychloridejand styrene polymers and copolymers; solid polychlorophenols; bitumen; waxes; and solid fertilisers, for example superphosphates.

Suitable liquid carriers includewater; alcohols, for example isopropanol and glycols; ketones, for exam ple acetone, methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; ethers; aromatic or araliphatic hydrocarbons, for example benzene, toluene and xylene; petroleum fractions, for example kerosineand lightmineral oils; chlorinated hydrocarbons, for example carbon tetrachloride, perchlor oethylene and trichiororethane. Mixtures of different liquids are often suitable.

Agricultural compositions are often formulated and transported in a concentrated form which is subsequently diluted bythe user before application.

The presence of small amounts of a carrier which is a surface-active agent facilitates this process of dilution. Thus preferably at least one carrier in a composition according to the invention is a surfaceactive agent. For example the composition may contain at leasttwo carriers, at least one ofwhich is a surface-active agent.

A surface-active agent may be an emulsifying agent, a dispersing agent or a wetting agent; it may be nonionic or ionic. Examples of suitable surfaceactive agents include the sodium or calcium salts of polyacrylic acids and lignin sulphonic acids; the condensation offatty acids or aliphatic amines or amides containing at least 12 carbon atoms in the molecule with ethylene oxide and/or propylene oxide; fatty acid esters of glycerol, sorbitol, sucrose or pentaeryth ritol; condensates of these with ethylene oxide and/or propylene oxide; condensation products of fatty alcohol or alkyl phenols, for example p-octylphenol or p-octylcresol, with ethylene oxide and/or propylene oxide; suiphates or sulphonates ofthese condensation products; alkali or alkaline earth metal salts, preferably sodium salts, of sulphuric or sulphonic 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 dodecylbenzene sulphonate; and polymers of ethylene oxide and copolymers of ethylene oxide and propylene oxide.

The compositions ofthe 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 or 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) andlor other additives such as penetrants or stickers. Dusts are usually formulated as a dust concentrate having a similarcomposition to that of a wettable powder but without a dispersant, and are diluted in the field with further solid carrier to give a composition usually containing 1/2-10% 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 0.5% w active ingredient and 0-10% w of additives such as stabilisers, surfactants, slow release modifiers and binding agents. The so-called "dry flowable powders" consist of relatively small granules having a relatively high concentration of active ingredient. Emulsifiable concentrates usually contain, in addition to a solvent and, when necessary, co-solvent, 10-50% w/v active ingredient, 2-20% w/v emulsifiers and 0-28% 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% wactive ingredient, 0.5-1 5 iS w of dispersing agents, 0.1-10% w of suspending agents such as protective colloids andthixotropic 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 forwater.

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

The composition ofthe invention may also contain otheringredients,for example other compounds possessing herbicidal, insecticidal or fungicidal properties.

The compounds offormula (I) in the form of trans enam,olner pairs may be obtained using convention ai techniques, forexample they may be obtained from the racemic com pou nds offormula (I) by expioiting the unique physical properties of each of the fourenantiomer pairs. Thus,forexample,the enantiomer pairs may be separated by high-performance liquid chromatography. Seefor example Jour- nal of Chromatography, 258(1983)175-182.

The following Example illustrates the invention.

Example Dsterrnination of Activity The activity of test compounds against colorado beetle larvae (Lep,inotarsa decemlineata), was deter- mined according to the following method.

;nsects were individually enclosed in cells of 4 cm diameter between two sheets of ground glass which had been coated with a dryfilm of a known concentration of testcompound, after 24 hours, the number of insects affected, being the nurnber of dead or moribund insects, was counted. From the observed effects ofthe test compounds on the insects over a range of concentrations, the dose required to affect 50% of the insects (ED50) in grams per hectare was calculated.

The results of tests using cypermethrin in the form ofthetransenantiometer pairs are given in Table 1.

Table 1

Test compound ED5o [1R trans]S + [15 trans 0.0017 [1R trans]R + [1S trans]S 0.26 Using the same method, the activity of test compounds against ladybird adults (Coccinella septempunctata) and carabid adults (Agonum dorsale) was determined.

The selectivity of a compound between colorado beetle and a beneficial insect may be expressed as the selectivity factor where the selectivity factor is defined as the ED50forthe beneficial insect divided by the ED50 for colorado beetles. Thus a large selectivity factor indicates a high level of selectivity. The following Table 2 gives the selectivity factors which were determined for the test compounds.

Table 2

Test Compound Selectivity Factor Ladybirds Carabids Cypermeth rin 54 52 Cypermethrin in the form of a mixture of4cisisomers 20 12 Cypermethrin in the form of a mixture of 4 trans isomers 9 17 Cypermethrin in the form of the [1R trans]S and [1S transit enantiomer pair 1218 2T76 Cypermethrin in the form of the [1R trans and [1S trans]S enantiomer pair 4045 3240 It is clear form Table 2 that the selectivity of cypermethrin in the form of either of the trans enantiomer pairs between colorado beetles and either ladybirdsorcarabids is outstandingly good.

Claims (5)

1. A method for combatting colorado beetles at a locus, which comprises applying to the locus an effective amount of a compound offormula:

wkerein R represents a halogen atom or a methyl group; R2 represents an halogen atomo or a methyl or trifluoromethyl group; and X presents a hydrogen atom or a fluorine atom; in the form of a trans enantiomerpair consisting of eitherthe [IR trans]S and [15 transiR orthe [1R trans]R and [iS transiS isomers.

2. A method as claimed in claim 1 wherein the locus is a potato plant.

3. A method as claimed in claim 1 or 2 wherein the compound offormula (1) is cypermethnn

4. A pesticidal composition which comprises a compound offormula (I) in the form of arans enantiomer pair as defined in claims 1 to 3 together with a carrier.

5. A composition as claimed in claim 4 which comprises at least two carriers, at least one of which is a surface active agent.