WO1993007750A1 - Control of insects - Google Patents

Abstract

A method of controlling insects on plants which comprises the application to the plant of an effective amount of an aqueous formulation that contains a pyrethroid insecticide as active ingredient, an evaporation retardant and an emulsifier, optionally together with a carrier or solvent for the active ingredient, which the formulation satisfies the formula: mass of oil phase/mass of retardant « Moil/M¿retardant? . X Exp[[ln(L/4)+[C x ln(AX?B¿)]]/C] where L is less than or equal to 15, A = 700376, B = -1.51, C = 0.8472, M¿oil? is the weighted average relative molar mass of the oil phase, M¿retardant? is the average molar mass of the retardant, and X = Moil?1.8¿ / Y where Y is the molar solubility ratio of the formulation, defined as the minimum number of moles of oil phase which will dissolve the retardant, divided by the number of moles of retardant, provided that, in the formula above, any solvent which has no liquid phase at 27 °C at atmospheric pressure is excluded.

Description

CONTROL OF INSECTS

The present invention relates to a method of controlling the damage caused by phytophagus insects to crops by the

application of an anti-evaporant formulation containing an insecticide.

European Patent Specification 331474 discloses spray

formulations which have evaporation retardant properties such formulations contain an oil phase, a retardant and an active ingredient, for example a pesticide.

Mite resurgance is a phenomenon encountered when broad

spectrum insecticides, such as the pyrethroids, are used to control insects on crops. Treatment with the pyrethroids controls the major pest on the crops, for example

caterpillars, but results in an explosion of the mite

population which was previously at a low density (mite

resurgance). One reason for mite resurgance is that the pyrethroids stimulate the mites to increase their

reproductive rate.

It has now been found that formulations of European Patent Specification 331474 containing a pyrethroid can be applied crops without causing mite resurgance.

Accordingly, the present invention provides a method of controlling insects on plants which comprises the application to the plant of an effective amount of an aqueous formulation that contains a pyrethroid insecticide as active ingredient, an evaporation retardant and an emulsifier that satisfies formula: mass of oil phase

≤

mass of retardant M_oil

. X Exp[[ln(L/4)+[C x ln(AX^B) ] ]/C] M_retardant where L is less than or equal to 15, A = 700376, B = -1.5 C = 0.8472,

Moil is ttιe weighted average relative molar mass of the o phase

M_retardant is the average molar mass of the retardant, an x ^{= M}oil^1.8 / ^γ where Y is the molar solubility ratio of the formulation, defined as the minimum number of moles of oil phase which will dissolve the retardant, divided by the number of moles of retardant, provided that, in the Formula above, any solvent which has no liquid phase at 27ºC at atmospheric pressure is excluded. The "oil phase" is the liquid non aqueous phase and will comprise one or more of the active ingredient, the solvent therefore and in some cases the emulsifier.

For the avoidance of doubt, and to clarify any ambiguities which may arise in the printing or copying of this

specification, it is to be noted that the relational symbol "≤" in the Formula is "less than or equal to", "Exp" means the exponential of what follows in brackets, "ln" means the natural logarithm, i.e. log_e, L is divided by 4, X is raise to the power B, B is a negative value (minus 1.51) and, in the definition of X, Moil is raised to the power 1.8.

Preferably L is less than 12, 10, or 8 and is most preferably less than 5. A distilled water spray has an "L" value of about 26, and most conventional diluted formulations have value of about 22-30. In the formulations of the invention, "L" can be set at a desired value in order to calculate the required ratios of the ingredients. M_oil' the average molecular weight of the oil phase, is the weighted average, i.e. taking into account the relative proportions of the ingredients. The value "Y", namely the molar solubility ratio of the formulation, may be derived empirically by making up at 40ºC a series of mixtures with different ratios of oil phase to alkanol, allowing the mixtures to cool to 27ºC, leaving the cool mixtures for at least 48 hours at 27°C, and determining the amount, in moles, of the oil phase which is needed to dissolve completely a given amount of retardant, in moles. The former is then divided by the latter to give Y.

Examples of pyrethroid insecticides include those of the formula (I)

where R is

or

R₁ is halo, CF₃ or CHF₂O, R₂ is hydrogen or halo, n is 0 or and Z and Z₁ are each independently selected from halo, CF0 and methyl, or Z(Z₁)C= represents :

X is hydrogen or halo, and X is H, CN or C≡CH,

or pyrethroids of formula :

or

Examples of pyrethroids are :

3-phenoxybenzyl-(IRS)-cis,trans-3-(2,2-dichlorovinyl-2,2-dimethylcyclopropanecarboxylate (permethrin),

(RS)-α-cyano-3-phenoxybenzyl-(1RS)-cis,trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate (cypermethrin) and its individual isomers such as the (1RS) cis isomer (alphamethrin) and the four isomer mixture betamethrin,

(S)-α-cyano-3-phenoxybenzyl-(1R)-cis-3-(2,2-dibromovinyl)-2 dimethylcyclopropanecarboxylate (deltamethrin), or a reaction mixture comprising two enantiomeric pairs in approximately ratio 2:3,

(S)-α-cyano-3-phenoxybenzyl-(1R)-cis-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropanecarboxylate,

(R)-α-cyano-3-phenoxybenzyl-(1S)-cis-3-(2,2-dichloro- vinyl)-2,2-dimethylcyclopropanecarboxylate with (S)-α-cyano-3- phenoxybenzyl-(1R)-trans-3-(2,2-dichloroviny1)-2,2- dimethylcyclopropanecarboxylate

(R)-α-cyano-3-phenoxybenzyl-(1S)-trans-3-(2,2-dichlorovinyl) 2,2-dimethylcyclopropanecarboxylate (beta-cypermethrin),

(RS)-α-cyano-3-phenoxybenzyl-(Z)-(1RS)-cis-3-(2-chloro-3,3,3 trifluoropropenyl)-2,2-dimethylcyclopropanecarboxylate

(cyhalothrin) and a mixture of its (S)(Z)-(1R)-cis and (R)(Z (1S)-cis-isomers,

(S)-α-cyano-3-phenoxybenzyl-(1R,3S)-3-[(Z)-3-[bis(trifluoro- methyl)methoxy]-3-oxo-1-propenyl]-2,2-dimethylcyclopropane- carboxylate (acrinathrin),

(RS)-α-cyano-3-phenoxybenzyl-(RS)-2-(4-chlorophenyl)-3- methylbutyrate (fenvalerate) and the single (S), (S) isomer (esfenvalerate),

(RS)-α-cyano-3-phenoxybenzyl-(S)-2-(4-difluoromethoxy- phenyl)-3-methyl butyrate (flucythinate),

(RS)-α-cyano-3-phenoxybenzyl-N-(2-chloro-α,α,α-trifluoro-p- tolyl)-D-valinate (fluvalinate),

(RS)-α-cyano-4-fluoro-3-phenoxybenzyl-(1RS)-cis-trans-3-(2,2 dichlorovinyl)-2,2-di-methylcyclopropanecarboxylate

(cyfluthrin),

(RS)-c.-cyano-4-fluoro-3-phenoxybenzyl-(1RS)-cis-trans-3-(2-chloro-2 ( 4 -chlorophenyl ) vinyl ) -2 , 2-dimethylcyclopropanecarboxylate (flumethrin), 2-methylbiphenyl-3-yl-methyl-(Z)-(1RS,3RS)-3-(2-chloro-3,3,3-trifluoro-prop-1-enyl)-2,2-dimethylcyclopropanecarboxylate (Bifenthrin);

the allethrins, for example (1RS)-3-allyl-2-methyl-4- oxocylopent-2-enyl-(1R,3R)-2,2-dimethyl-3-(2-methylprop-1- enyl)-cyclopropanecarboxylate (bioallethrin),

(1S)-allyl-2-methyl-4-oxocyclopent-2-enyl-(1R,3R)-2,2- dimethyl-3-(2-methylprop-1-enyl) cyclopropanecarboxylate (S- bioallethrin), and mixtures of allethrin isomers (esbiothriin); the resmethrins, for example 5-benzyl-3-furylmethyl(IRS, 3RS; 1RS, 3SR)-2,2-dimethyl-3-(2-methyl-prop-1-enyl) cyclopropan carboxylate (resmethrin) and 5-benzyl-3-furylmethyl (1R,3R) 2,2-dimethyl-3-(2-methylprop-1-enyl) cyclopropanecarboxylate (bioresmethrin).

Octadecan-1-ol and, particularly, hexadecan-1-ol are preferred evaporation retardants. Hexadecan-1-ol (also known as cetyl alcohol) is usually available commercially as a mixture with a minor proportion of octadecan-1-ol (stearyl alcohol) and such "cetostearyl alcohol" is quite satisfactory.

Heptadecan-1-ol performs adequately but is much more

expensive. Other highly effective evaporation retardants include 1-hexadecylamine, 1-heptadecylamine and 1- octadecylamine. Less preferred evaporation retardants include hexadecan-2-ol, 1,2-hexadecandiol, methyl stearate, stearyl acetate, methyl palmitate and 1,2-octadecandiol. N-alkoxyalkanols may be used, for example CH₃ (CH₂)₂₁OC₂H₄OH,

CH₃(CH₂)₂₁OC₃H₆OH, CH₃(CH₂)₁₇OC₂H₄OH or CH₃ (CH₂) ₁₅OC₂H₄OH, as may oxyethylene-docosanol and mixtures of any of the said evaporation retardants.

The amount of emulsifier present in the formulation will be less than twice the amount of the evaporation retardent present and will preferably be less than the amount of the evaporation retardant present.

The emulsifier may be any suitable compound or mixture of.

compounds. Cationic emulsifiers can be used, but they tend to irritate the user's eyes. Anionic emulsifiers such as calcium dodecyl benzenesulphate (CDBS) or sodium d-isopropyl naphthalenesulphonate (SDNS) can also be used, but these are not as effective at stabilising the emulsion whilst

maintaining evaporation retarding properties. Preferably, the emulsifier is a non-ionic compound, or mixture of non-ionic compounds, having an HLB (hydrophilic/lipophilic balance) 6-20 and preferably 8-18. Suitable compounds include polyoxyethylene stearyl ethers (PSE), polyoxyethylene monolaurates (PEM), polyoxyethylene mono-oleates (PMO), sorbitan mono-oleate (SMO), nonylphenol ethoxylate (NPE), polyethylene glycol (PEG) and blends of oleyl ethoxylate (1 mole), and PEG20 glyceryl oleate (OE/PGO). These emulsifiers are available as follows:

Abbrev. Trade name Supplier

OE/PGO Tegoplant Th.

EM11 Goldschmidt

Ltd.

PSE Brij 72, Brij 76, ICI Speciality

Brij 78 Chemicals

PEM Tween 20 ICI Speciality

Chemicals

SMO Span 80 ICI Speciality

Chemicals

PMO Tween 80 ICI Speciality

Chemicals

NPE Ethylan Lankro

KEO,55,BV Chemicals

Limited

CDBS Arylan CA Lankro

Chemicals

Limited

SDN Aerosol OS Cyanamid GB

Ltd.

The solvent, at least for an oil-soluble active ingredient, preferably has a low relative molecular mass, namely less than about 200.

Suitable compounds include aromatic hydrocarbons, lower alky esters, lower ketones, lower alkanols and lower alkanes, the term "lower" meaning C1-12, preferably C1-10 and more preferably C1-8.

Particular solvents include the following, all available from Exxon Chemicals Limited;

"Solvesso 150" - An aromatic hydrocarbon solvent (C9 to C11) with a distillation range 190 to 210ºC.

"Solvesso 200" - An aromatic hydrocarbon solvent (C10 to C12) with a distillation range 226 to 290°C.

"Exxate 700" - Heptyl acetate 99% pure, or

Odourless kerosene - A mixture of high boiling non-aromatic hydrocarbons consisting of paraffins and naphthenes with a distillation range of 180 to 270°C.

The formulation may comprise more than one pyrethroid

(optionally with a synergist or potentiator, which is

regarded as an active ingredient for the purpose of the

Formula above), more than one solvent., more than one

emulsifier and/or more than one stabiliser, together with other ingredients such as perfumes and dyes.

The present invention also provides a method for preventing the resurgance of mite infestation in plants when treated with pyrethroid insecticides which comprises the application to the plant of an aqueous formulation that contains the

pyrethroid insecticide as active ingredient, an evaporation retardant and an emulsifier that satisfies the Formula described hereinbefore.

The following examples illustrate representative formulations to be applied and the biological properties of such

formulations: Example 1 (Formulation 1)

Ingredient % w/w

Permethrin (Technical) 10.32 Piperonyl Butoxide (Technical) 12.83

Cetyl Alcohol 3.00

Odourless Kerosene 9.70

Emulsifier Blend 1.00

Deionised Water 62.75

Silcolapse 5000 0.10

Formaldehyde Solution 0.30

100.00 1% Emulsifier Blend consists of 0.75% Emulgator BTO2, 0.1% BRIJ 78, 0.1% BRIJ 72 and 0.05% TWEEN20.

Emulgator BT02 is equivalent to Tegoplant EMU described in European Patent 331474.

Biological Properties

150lm Diameter droplets of Ambush™ (which is a formulation marketed by ICI Americas Inc) and formulation 1 were applied to 2cm diameter leaf discs cut from "Henderson" lima beans. Both formulations were mixed in water at a rate of 12.5g a.i per liter.

Droplets were applied at densities of 25, 50, 75, 100, 150 and 200 per leaf disc. Five replicate leaf discs were used per droplet density. Five replicate control leaf discs were left untreated.

Leaf discs were left to dry for one hour. Five adult female two-spotted spider mites (TSSM) were then placed on each leaft disc using a fine camel-hair brush. The mites were obtained from cultures reared on greenhouse lima beans at the OARDC. The leaf discs were placed on moistened cotton in 3cm

diameter petri dishes and were maintained in the laboratory at room temperature (22-25ºC).

At 24 and 48 hours following treatment, the following were assessed: mortality, the number of mites on and off the leaf disc, the number of eggs and the number of feeding scars. Mites were recorded as dead when they would not respond to gentle prodding. For each parameter measured the data were analysed using a one-way analysis of variance. Significant treatment effects were partitioned using a Student-Newman-Keuls (SNK) multiple range test. Prior to analyses, the data were first

transformed using either percentages and arcsin-squareroot (mortality, irritanσy) or log10 n+1 (eggs/mite, scars/mite) The effects of droplet density upon the parameters measured were then subsequently analysed using linear regression analyses. The individual treatment means and the results of the SNK multiple range test were plotted for irritancy, fecundity and feeding rate at 24 hours after exposure.

Significant treatment effects were detected in the

measurements of irritancy, fecundity and feeding rate but not in the measurement of mortality. In all, very few mites died throughout the study, in any of the treatments. This was expected as the rates of permethrin that were chosen were selected in order to investigate the sub-lethal effects of these pesticides upon TSSM.

For all the parameters measured, no treatment effects were detected for formulation 1. However, significant treatment effects were detected with Ambush. By increasing the droplet density, it was observed with

Ambush, a significant increase in the number of TSSM leaving the leaf, which took place concomitant with a significant decrease in the number of eggs laid and the amount of feeding activity (despite a correction for the number of TSSM that remained on the leaf).

Claims

1.- A method of controlling insects on plants which compris the application to the plant of an effective amount of an aqueous formulation that contains a pyrethroid insecticide active ingredient, an evaporation retardant and an

emulsifier, optionally together with a carrier or solvent for the active ingredient, which the formulation satisfies the formula: mass of oil phase mass of retardant Moil

. X Exp[[ln(L/4)+[C x ln(AX^B)]]/C]

^Mretardant where L is less than or equal to 15, A = 700376, B = -1.51, C = 0.8472,

^Moil is the weighted average relative molar mass of the oil phase

M_retardant is the average molar mass of the retardant, and X = M_oi! ^1.8 / Y where Y is the molar solubility ratio of the formulation, defined as the minimum number of moles of oil phase which will dissolve the retardant, divided by the number of moles of retardant, provided that, in the Formula above, any solvent which has no liquid phase at 27ºC at atmospheric pressure is excluded.

2.- A method for preventing the resurgence of mite

infestation in a plant when treated with pyrethroid

insecticides which comprises the application to the plant of an effective amount of a formulation as defined in claim 1.

3.- A method as claimed in claim 1 or claim 2 in which the formulation optionally comprises more than one pyrethroid (optionally with a synergist or potentiator, which is regarded as an active ingredient for the purpose of the formula in claim 1), and/or more than one solvent, and/or more than on emulsifier and/or more than one retardant, optionally together with other ingredients selected from perfumes and dyes.

4.- A method as claimed in any one of claims 1 to 3 in which the pyrethroid insecticides is either

(a) a compound of formula (I)

wherein R represents

or

in which R₁ is halo, CF₃ or CHF₂O, R₂ represents hydrogen or halo, n is 0 or 1, and Z and Z₁ are each independently selected from halo, CF₃ and methyl ; or Z(Z₁)C= represents

X represents hydrogen or halo, and X is H, CN or C≡CH, in the form or individual isomers or mixtures thereof;

or

(b) a compound of formula :

or

in the form of individual isomers ir mixtures thereof;

or

(c) a compound selected from flumethrin, bifenthrin,

bioallethrin, S-bioallethrin, esbiothrin, resmethrin,

bioremesthrin and acrinathrin.

5.- A method as claimed in any one of claims 1 to 4 wherein is less than 10.

6.- A method as claimed in claim 5 wherein L is less than 5.

7.- A method as claimed in any one of claims 1 to 6 where the amount of emulsifier present in the formulation is less than twice the amount of the evaporation retardant present.

8.- A method as claimed in claim 7 wherein the amount of emulsifier present in the formulation is less than the amount of the evaporation retardant present.

9.- A method as claimed in any one of claims 1 to 8 whereii the emulsifier is a non-ionic compound with an HLB

(hydrophilic/lipophilic balance) value of 8-18, or a mixture of non-ionic compounds, the mixture having a weighted average HLB value of 8-18.

10.- A method of claimed in any one of the preceding claims wherein the evaporation retardant is hexadecan-1-ol,

octadecan-1-ol or a mixture thereof.