SI9210068A - Novel insecticide pyrethroid composition consist of new combination of cipermetrin isomers - Google Patents

Abstract

A compound having four isomers derived from racemic cis / trans-3- (2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarboxylic acids and (S) (cyano) (3-phenoxyphenyl) methanol, is twice as effective as cypermethrin against some types of insects, but quite unexpectedly significantly less toxic to mammals and certain types of fish at doses that give it commercially an acceptable control of insects that attack crops.

Description

NEW INSECTICIDE PYRETHROID COMPOSITIONS CONCERNING 12

NEW CIPERMETRINE ISOMER COMBINATIONS

The present invention relates to pyrethroid insecticides, more specifically to a composition consisting of a novel combination of isomers (cyano) (3-phenoxyphenyl ') methyl 3- (2,2dichloroethenyl) -2,2-dimethylcyclopropanecarboxylate, commonly known as cypermethrin. Cypermethrin, with its three optical centers, consists of eight isomers.

After Elliot et al. photostable pyrethroids and high insecticidal activity of one isomer, (S) (cyano) (3-phenoxyphenyl) methyl (IR, cis) -3- (2,2dibromoethenyl) -2,2-dimethylcyclopropanecarboxylate (hereinafter '1R-cis-S') isomer), which is published in Nature (1974), 248, 710 and in the US Pat. No. No. 4,024,163, the scientific and patent literature was full of methods for the preparation of individual isomers and selected combinations of cypermethrin isomers, methods for enriching mixtures of isomers with more active isomers, and descriptions of the compositions obtained. U.S. Pat. No. 4,136,195 discloses lR-cis-S and IR-cis-R isomers of cypermethrin. U.S. Pat. No. No. 4,133,826 discloses a method for converting the IR-cis-R isomer of cypermethrin to the more active IR-cis-S isomer. U.S. Pat. No. No. 4,308,279 discloses a compound containing substantially equimolamous amounts of the cyrmethrin isomers of the lR-cis-S and IS-cis-R isomers and a process for its preparation from the four cis isomers of cypermethrin. U.S. Pat. No. No. 4,845,126 discloses a suitable combination of the IR-trans-S and IS-trans-R isomers of cypermethrin. U.S. Pat. No. No. 5,028,731 discloses a process for the preparation of certain pyrethroid insecticides including a compound of the present invention.

Today, both individual isomers have dibromo pyrethroid, published by Elliot et al. as cypermethrin containing eight isomers is of great commercial importance and, as mentioned above, much attention is paid to the preparation of cypermethrin isomer selection with greater efficiency than cypermethrin itself. A more active product means a smaller dose and therefore less pesticide released into the environment. However, enriching the pyrethroid with a more active isomer raises the price of the product. For practical reasons, the manufacturer must be vigilant not to enrich the product to such an extent that the farmer would cost more to cultivate one hectare with an improved product than to treat it with a non-enriched pyrethroid or alternative product. However, incremental improvements can be commercially important, especially when efficiency gains or reduced environmental impacts can be achieved without increasing the cost to the farmer. These considerations result in various attempts to find exactly the right balance of cypermethrin isomers, which will give the farmer a significant advantage without disproportionately increasing costs.

Despite extensive studies of cypermethrin and its isomers, and many publications on individual isomers and combinations of cypermethrin isomers, the novel composition disclosed herein has not been discovered before the present invention, nor has it been appreciated.

In conventional cypermethrin preparations, the acidic portion is prepared as a cis / trans racemic mixture, which is then converted to acid chloride and treated with racemic (cyano) (3-phenoxyphenyl) -methanol (prepared in situ from 3-phenoxybenzaldehyde and sodium cyanide). We have now discovered that a four-isomer composition derived from racemic cis / trans acid chloride and (S) (cyano) (3-phenoxyphenyl) methanol, a compound referred to herein as sigma-eipermetrin, is twice as effective as cypermethrin against certain insect species , but quite unexpectedly less toxic to mammals and certain species of fish at doses that give commercially acceptable control of insects that attack crops. Therefore, the use of sigma-cypermethrin instead of cypermethrin (1) halves the amount of pesticide applied to the environment, (2) reduces the risk of fish being killed as a result of the pesticide entering the lakes or rivers through surface runoff, (3) reducing the pesticide exposure of persons , which apply to those who may enter the treated field shortly after spraying, (4) reduce the amount of residue that may remain in the harvested field. In addition, since sigma-cypermethrin can be prepared as a direct reaction product of racemic cis / trans acid chloride and (S) (cyano) (3-phenoxyphenyl) methanol, there is no need for an additional step of selective crystallization or epimerization of cypermethrin, as used in some previous of cypermethrin isomer selection preparations.

In most of the methods commonly used to make 3- (2,2-dichloroethenyl) 2,2-dimethylcyclopropane carboxylic acid in the form of chloride, the concentrations of lS-cis lR-cis, lS-trans and IR-trans isomers are approximately the same. For the purposes of this application, the cis / trans distribution can be considered to be approximately the same if the compound consists of 50 ± 5% of each isomer. Unless otherwise stated, the term sigma-cypermethrin means a product in which the cis / trans ratio is 45-55 / 55-45, but more often this ratio will be 48-52 / 52-48.

When prepared in large quantities, as in the preparation of what is known in the agricultural chemical industry as a technical product, sigma-cypermethrin, as long as it consists primarily of the S-isomers of cypermethrin, will contain smaller amounts of R-isomers, thanks to its R content (S) (cyano) (3-phenoxyphenyl) methanol as well as unconverted starting material and by-products. For the purposes of this application, the ratio of S / R isomers in (S) (cyano) (3-phenoxyphenyl) methanol is at least 9/1. For the purposes of this declaration, sigma-cypermethrin means a product consisting essentially of at least 88% of the total isomer of cypermethrin and at least 80% of the S-isomer of cypermethrin, the remainder being the unconverted starting material, including the side components present in the starting materials, and the side products of conversion to sigma-cypermethrin and does not contain anything that would significantly affect the usefulness of the product as a pyrethroid insecticide. A typical technical product of sigma-cypermethrin contains 89.1% of all cypermethrin isomers and 82.9% of S-isomers, the only other compounds present in 1% or more being 3-phenoxybenzaldehyde (3.56%) and (±) (cyano) (3-phenoxyphenyl) methanol (1.93%).

Methods for the preparation of (S) (cyano) (3-phenoxyphenyl) methanol esters are illustrated in the following examples.

EXAMPLE 1

PREPARATION OF VA (S) (CYANO) (3-PHENOXYPHENYL) METHYL CIS / TRANS-3- (2.2-DICLOROETHENYL) -2.2-DIMETHYLCYCLOPROPANECARBOXYL TA

Step A Preparation of (S) (Aminocarbonyl) (3-phenoxyphenyl) methyl cis / trans-3 (2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarboxylate

A mixture of 10.7 g (0.044 mol) of (S) -3-phenoxymandelamide (prepared by method US 4,146,554) was heated to 40 ° C, during which time 8 mL of pyridine was added, resulting in complete dissolution of the solid, which was present in the initial mixture. The heating was stopped and 10.0 g (0.044 mol) of cis / trans-3- (2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarbonyl chloride in 10 mL of toluene was added dropwise over 15 minutes. The mixture was stirred at room temperature for about 17 hours and then 35 mL of 1N hydrochloric acid was added. After stirring for 30 minutes, the mixture was poured into a separatory funnel and 60 ml of diethyl ether added. The organic phase was separated and washed twice with 40 mL of saturated sodium chloride solution. After drying over anhydrous magnesium sulfate, the solvent was removed under reduced pressure to leave a gold, viscous residue of (S) - (aminocarbonyl) (3-phenoxyphenyl) methyl cis / trans-3- (2.2-dichloroethenyl) 2.2- dimethylcyclopropanecarboxy-lata. which weighed 19.0 g.

Step B Preparation of (S) (cyano) (3-phenoxyphenyl) methyl cis / trans-3 (2,2-dichloroethenyl) -2,2-dimethylcyclopropanecarboxylate

To a solution of 19.0 g (0.043 mol) (S) (aminocarbonyl) (3-phenoxyphenyl) methyl cis / trans-3- (2,2-dichlorophenyl) -2,2-dimethylcyclopropanecarboxylate in 35 mL of methylene chloride under nitrogen was added 55 mL of pyridine. This mixture was cooled to -5 ° C and 12.6 g (0.081 mol) of phosphorus oxychloride in 10 mL of methylene chloride was added dropwise over 20 minutes. After the addition was complete, the mixture was stirred at 0 ° C for one hour, then poured into a mixture of 200 mL of 1N hydrochloric acid and crushed ice. The organic and aqueous phases were separated and the organic phase was washed first with 50 mL of saturated aqueous sodium chloride solution and then with 1 N hydrochloric acid. This solution was dried over anhydrous magnesium sulfate and the solvent removed under reduced pressure to give a light orange oil, which weighed 17.7 g, as a residue. This oil was passed through a column of Florisil® adsorbent and eluted with methylene chloride. The fractions containing the desired product were combined and the solvent was evaporated under reduced pressure to give a light yellow oil, which weighed 12 g, as a residue. This residue was determined by HPLC to contain 39.2% of the cis-isomer and 58.0% of the (S) - (cyano) (3-phenoxyphenyl) methyl-3- (2,2-dichloroethenyl) -2,2 transisomer -dimethylcyclopropanecarboxylate.

[ct] ²⁵ = + 15.80 ° (c = 1.06; CHCl ₃ ); [α] ²⁵ = + 13.62 ° (c = 1.02; ethanol);

Calculated: C 63.47; H, 4.60; N, 3.15;

Found: C, 63.43; H, 4.60; N, 3.15.

EXAMPLE 2

PRI PR A V A (S) (Cyano) (3-Phenoxyphenyl) METHYL CIS / TRANS-3- (2,2-DICLOROETHENYL) -2,2-DIMETHYLCYCLOPROPANECARBOXYL TA

To a solution of 136.2 g (66.83% analysis, 0.400 mol) of cis / trans-3- (2,2 dichloroethenyl) -2,2-dimethylcyclopropanecarbonyl chloride in 75 mL of heptane under argon, 139.7 g (0.406) were added at reflux. moles) 65.5% solution of (S) (cyano) (3-phenoxyphenyl) methanol (containing 93% S-isomer, 7% R-isomer). The addition lasted 115 minutes and during this time the temperature remained in the range of 103-105 °

C. A solution of 10.8 g (0.060 mol) of 65.5% solution of (S) (cyano) (35 phenoxyphenyl) methanol was added. After the addition was complete, the mixture was heated at reflux for one hour. The mixture was then cooled to 90 ° C- and 100 mL of 10% sodium carbonate solution in water was added. This mixture was stirred for 0.5 hours and then maintained at 60 ° C for about 17 hours to allow complete separation. The aqueous phase was separated and discarded. The organic phase was washed once with water and the solvent was evaporated under reduced pressure to give 198.8 g of a liquid residue. Analysis of this residue by liquid chromatography determined that it contained 79.6% (S) (cyano) (3-phenoxyphenyl) methyl cis / trans-3- (2,2-dichlorophenyl) -2,2-dimethylcyclopropanecarboxylate. About 175 g of this product was dissolved in 100 mL of toluene. This solution was stirred vigorously for 29.5 hours with a solution of 40 g of sodium metabisulphite in 160 mL of water. After this time, the aqueous phase was separated and discarded, and the organic phase was washed with 200 mL of water. The organic phase solvent was then evaporated under reduced pressure to give a residue that weighed 129.8 g. Analysis of this residue by liquid chromatography determined that it contained 92.7% of all cypermethrin isomers, 86.2% (S) (cyano) (3-phenoxyphenyl) methyl eis / trans-3- (2.2-dichloroethenyl-2,2-dimethylethyl-opanecarboxylate and 6.5% of the R-isomer (the content of the isomer was estimated on the basis of the initial alcohol) and the cis / trans ratio was 49/51 (sigma-cypermethrin).

The sigma-cypermethrin preparations used in the following studies of insecticidal activity, mammalian toxicotoxicity and fish toxicity were prepared by the method illustrated in Example 2, which is U.S. Method. Pat. No. 5,028,731. In each case, the S- and R- ratios were evaluated based on the S / R ratio of starting material (S) (cyano) (3-l'noxyphenyl) methanol and total isomer analysis. Subsequent analysis studies showed that these estimates were reliable and accurate.

INSECTICIDE ACTIVITY

The insecticidal activity of sigma-cypermethrin was determined as follows:

Valuation per sheet

Cypermethrin and sigma-cypermethrin were tested by application on foliage at various concentrations in aqueous solutions containing 9.7% acetone and 0.25% octylphenoxypolyethoxyethanol. The insect species we used included the cabbage peduncle (Trichoplusia ni), the armyworm of the southern localities (Spodoptera eridania), the Mexican bean beetle (Epilachna varivestis), the tobacco Brussels worm (Heliothis virescens), and the corn-coiled worm (Heliothis virescens).

For all insects, plants of leafy beans (Phaseolus vulgaris) were treated with test solutions. The test solutions were applied with a sprayer to the upper and lower surfaces of the leaves so that they drained. We then let the plants dry and cut them at the base of the stem before placing them in the beakers. Ten individual insects of suitable species were placed in each beaker during the second stage of development, except for the tobacco-bud worm and the corn-coiled worm, and the beaker was covered. Four replicates were used in the experiments with tobacco Brussels sprouts and corn rootworm, each repetition comprising five insects in the second stage of development. Mortality was determined 48 hours later in all tests. The sigma-cypermethrin used for the evaluation on the leaf was the product of Example 2.

Below, we show the calculations based on these results: LC50 'values and relative efficiency Try LCsn'values (ppm) Relative types cypermethrin Cip-cypermethrin efficiency CL 2.3 1.4 1.6 MBB 1,2 0.3 4.0 SAW 4.2 1.8 2.3 TBW 7.3 4.4 1.7 TBVV-R 92 43 2.1 CEVV 7.3 3.9 1.9

CL = cabbage looper, Trichoplusia ni)

MBB = Mexican bean beetle, Epilachia varivestis

SAW = southern army worm, Spodoptera eridania

TBW = tobacco budworm, Heliothis virescens

TBW-R = Pyrethroid resistant tobacco budworm strain

CEW = corn earworm, Heliothis zea

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The above laboratory results show that sigmacipermetrin is significantly more effective against different insects than cypermethrin, on average almost twice (1.9 times) more effective against Lepidoptera and four times more effective against the only Coleoptera species tested. In practical terms, this means that sigma-cypermethrin in the field can be expected to be effective at about half the dose required for cypermethrin, and this has been shown to be accurate.

Try the box

Field experiments conducted on cotton in Louisiana, Mississippi, Alabama, and Arizona were modeled to randomly block four repetitions at one go. The plots measured a minimum of 8,932 acres and all applications were made with commercial field equipment, with a minimum of 0.935 1 per en ar of total sprinkler solution. The cypermethrin isomer content (% by weight) of some sigma-cypermethrin technical products used in the field experiments were as follows:

Leto

Total isomers

S-isomers of cis / trans ratio

1 91,5 85 54/46 2 88,3 82 52/48 88,3 82 51/49 3 89,1 82 51/49

Data analysis was performed on the basis of the seasonal average of several evaluations carried out over four to six weeks (3-4 repetitions) in the control experiments of Heliothis sp. The results are shown below.

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Experiments in a California salad field, designed to evaluate the control of herbaceous pedicels, consisted of a model for randomly blocking four repetitions in one procedure. Applications were made on small plots with CO2 spray in a backpack using at least 0.935 1 per acre. The results were converted to percentage control based on untreated control plots. We present these results below:

COMPARISON OF CYPERMETRINE AND Σ-CYPERMETRINE% control of herbaceous pedicel

Dose Year 1 (DPP) Year 2 (DPP) ** Process (kg / a) 3 7 3 7 Cip-cypermethrin l, 46xl0- ⁴ - - 98 71 2,92x10-4 83 90 98 91 4,38x10-4 - - '100 98 Cypermethrin 6,74x10-4 61 78 94 81

DPP = Days After Procedure * Average of 2 Trials (CA #) ** Average of 1 Trial (CA #) # California

Field experiments were conducted in Louisiana, North Carolina, Texas, Kentacky, Tennessee, and Illinois to evaluate the control of black alfalfa (Hypera postica). We used small test plots according to the model for random blocking with four repetitions per procedure. We made applications with CO2 sprayers in a backpack. The results were obtained 3, 7 and 14 days after the procedure (DPP) and were converted to percentage control based on untreated control.

COMPARISON OF CYPERMETRINE AND Σ-CYPERMETRINE% control of black alfalfa

Dose Letol (DPP) * Year 2 (DPP) ** Process (kg / a) 3 7, 14 3 7 14 Cip-cypermethrin l, 12xl0- ⁴ - - - 93 93 85 1,65x10-4 - - - 94 97 94 2,47x10-4 96 94 96 94 96 94 Cypermethrin 4,49x10-4 - - - 94 96 90

DPP = days after procedure * Average of 4 trials (LA, NC, ΤΧ, KY #) ** Average of 6 trials (TN, KY, NC, LA, IL, TX #) # LA = Louisiana; NC = North Carolina; TX = Texas; KY = Kentucky; TN = Tennessee; IL = Illinois

In each of the field experiments reported above, sigmacipermetrin, at half a dose of cypermethrin or even less, usually yielded results substantially identical to those obtained with cypermethrin administered at the recommended dose, sometimes marginally better. , sometimes worse. Even where cypermethrin may appear to have a marginal advantage, albeit at a double dose, sigma-cypermethrin gave commercially acceptable control.

TOXICOLOGY

Sigma cypermethrin has shown surprising advantages with respect to the parent compound cypermethrin, both in mammalian and fish toxicology.

Feeding study for 90 days

In a 90-day feeding study conducted according to EPA guideline 82-1, the test compound was continuously administered in the feed to groups of rats for at least ninety days, at concentrations of 0, 150, and 1500 ppm groups of fifteen Sprague-Dawley rats for cypermethrin and 0, 10, 50, 150, 250, 500 and 900 ppm groups of ten Fisher 344 rats for sigma-ciprmethrin. (Doses for sigmacipermetrin were lower because we expected it to be more toxic than cypermethrin). The content of cypermethrin isomers (% by weight) in the sigma-cypermethrin technical product used in this study was: total isomers - 88.2%, S-isomers - 82%, cis / trans ratio - 53/47. We registered the values for individual weight and food consumption on a weekly basis. Finally, hematological and clinical-chemical determinations were performed and the weights of organs were obtained: adrenal glands, brain, heart, kidney, liver, and ovaries or testicles. A histopathological examination of approximately 40 tissues was performed on all animals in the control and highest dose cypermethrin groups and in the highest two groups (500 and 900 ppm) in the sigma-cypermethrin study. In addition, we performed a histopathological examination of the lungs, livers, and kidneys of animals in the medium dose groups of both studies (150 and 500 ppm for cypermethrin and 10, 50, 150, and 250 ppm for sigma-cypermethrin). An eye examination was performed on vsesh animals before the procedure was initiated and before the final sacrifice.

In these tests, the no observable effect level (NOEL) for cypermethrin was 150 ppm and for sigma-cypermethrin was 250. If sigma-cypermethrin, which is about twice as toxic to target insects as cypermethrin, for rats as toxic as for insects, would be expected to be half the value for NOEL than cypermethrin; but instead, it is more than one and a half times the value for cypermethrin. In other words, this study required more than three times more sigma-cypermethrin to show an effect on rats than would be expected based on the effect of cypermethrin on insects if the relative effect of sigma-cypermethrin and cypermethrin on rats was the same as the relative effect to insects.

Multi-generational study

Multi-generational studies have been performed according to EPA guideline 83-4 and provide information on reproductive parameters as well as on neonatal morbidity and mortality for multiple generations. Wistar rats were administered food containing 0, 50, 150, and 750 ppm of cypermethrin throughout the study (the highest dose level was 1000 ppm in the first 12 weeks but was reduced to 750 ppm due to toxicity in the rest of the study). Similarly, Spraguc-Dawlcy rats were given food containing 0, 7.5 25, 100, 375, and 750 ppm sigma-cypermethrin. (Again, the doses of sigma-cypermethrin were lower because we expected it to be more toxic.) The content of cypermethrin isomers (% by weight) in the technical product sigma-cypermethrin used in this study was: total isomers - 89. 1%, S-isomers - 82%, cis / trans ratio - 51/49. We observed daily mortality in rats and possible signs of the effects of the test substance. Body weights and food consumption were recorded at regular intervals.

We started breeding parenting and later generations with 30 females. In both studies, adequate concentrations of the test substance in the food were made possible during cohabitation. Exposure to parental males of each generation was continued until a predetermined sacrifice that followed the end of cohabitation periods, while exposure to parental females continued for the duration of deterring the puppies from breastfeeding. The pups were weaned in both studies within 28 days after birth. Due to the excess mortality that occurred in the case of Fj generation of the fetus (sigmacipermethrin) during the 28-day lactation period and the first week after weaning, this group was discontinued at the end of the third week after weaning.

In this study, the NOEL for cypermethrin was 50 ppm and for sigma-cypermethrin 100 ppm. In this case, too, the NOEL for sigma-cypermethrin is twice that for cypermethrin, but not half as much as would be expected based on the insect effect. This means that four times more sigma-cypermethrin is required to show an effect on rats than the amount you would expect based on the effect of cypermethrin on insects if the relative effect of sigma-cypermethrin and cypermethrin on rats were the same as the relative effect to insects.

Tcratology

These experiments were performed according to EPA guideline 83-3 for the purpose of determining the effects of the test substances on pregnancy and utero development. Experimental substances in corn oil were administered to Sprague-Dawley rats once a day, between day 6 and day 15 of suspected pregnancy, through a probe. There were 25 animals per dose group. Doses were given: 0, 17.5 37.5 and 75 mg / kg in the case of cypermethrin and 0, 5, 12.5 25, and 35 mg / kg in the case of sigma-cypermethrin. The content of cypermethrin isomers (% by weight) in the sigma-cypermethrin technical product used in this study was: total isomers - 89.1%, S-isomers - 82%, cis / trans ratio - 51/49. Control animals (O mg / kg) received corn oil during treatment. All doses were adjusted daily for body weight.

Rats were observed daily for dosing and dosing periods. We sacrificed rats on the 20th to 21st days of gestation to investigate the contents of their uterus, including the number of live and dead fetuses and the number of resorbs. We then examined the fetuses for deformity.

In this test, the NOEL for cypermethrin was 17.5 mg / kg and for sigma-cypermethrin

12.5. Thus, in this study, the amount of sigma-cypermethrin required to show an effect on rats was only 1.4 times less than what would be expected based on the effect of cypermethrin on insects if the relative effect of sigma-cypermethrin and cypermethrin on rats the same as the relative effect on insects. In the case of both compounds, there was no embryotoxic or teratogenic effect at either dose.

In short, in these well-established mammalian toxicology tests, sigmaeipermetrin showed an unexpected advantage over cypermethrin, which is not obvious, extending from 1.4 times to four times the amount of sigma-cypermethrin needed to show the effect expected on rats on based on the effect of cypermethrin on insects if the relative effect of sigma-cypermethrin and cypermethrin on rats was the same as the relative effect on insects.

Toxicity to fish

We conducted sixty-six acute toxicity studies of cypermethrin and sigma-cypermethrin on rainbow trout (Oncorhynchus mykiss) and American whiting (Cyprinodon variagatus) to determine the median lethal concentration (LC50) resulting from continuous exposure. In the case of rainbow trout, the exposure environment was spring water, and for American whitefish, seawater was filtered. Each group of twenty fish (10 per replicate aquarium) was exposed to one of five concentrations of pyrethroid added in the dimethylformamide (DMF) dilution system to 30 μ L / L DMF in the exposure medium (solvent control), or alone the exposure medium (control). Mortality, morbidity and other obvious signs of toxicity were determined at prescribed intervals. The concentrations of the test substances were measured at the beginning and at the end of the exposure using the submerged HPLC method. The content of cypermethrin isomers (% by weight) in the sigma-cypermethrin technical product used in this study was: total isomers - 88.2%, S-isomers - 82%, cis / trans ratio - 53/47.

The measured concentrations used in this test were:

for American whites:

for cypermethrin: 4.61, 2.14, 0.765, 0.601, 0.446 pg / L for sigma-cyperctrin: 3.00, 1.79, 0.91, 0.62, 0.28 pg / L for rainbow trout:

for cypermethrin: 2.24, 1.35, 0.719, 0.366, 0.219 pg / L for sigma-cypermethrin: 5.27, 2.77, 1.65, 0.82, 0.47 pg / L

Concentrations with no observable effect eoneentration (NOEC) and LC50 values found in the experiments were:

for American whites:

cypermethrin: NOEC - 2.14 pg / L, LC ^ g - 3.38 pg / L sigma-cypermethrin: NOEC ^1. -1.79 pg / L, LC50 - 2.37 pg / L in rainbow trout:

cypermethrin: NOEC-0,366 pg / L, LC50 - 0,897 pg / L sigma-cypermethrin: NOEC - 0,47 pg / L, LC50 - 0,69 pg / L

Since sigma-cypermethrin is about twice as toxic to commercially important insects as cypermethrin, the LC50 'for sigma-cypermethrin would be expected to be half the value for cypermethrin if twice as toxic to fish. Put differently, you would expect the LC50 ratio for cypermethrin and LC50 for sigma cypermethrin to be 2.0. Any other ratio means that sigmacipermetrin is less toxic to fish than would be expected based on its toxicity to insects. The ratio for rainbow trout is 1.3 and for the American white trout 1.64. Thus, sigmacipermetrin is less toxic to these two species of fish than would be expected based on the relative insect toxicity of these two products.

In summary, sigma-cypermethrin is twice as effective as cypermethrin against certain insect species that attack the most important crops, but significantly less toxic to mammals and species of fish at doses that allow the target crops to be commercially controlled. Therefore, the use of sigma-cypermethrin instead of cypermethrin halves the amount of insecticide applied to the environment, reduces the risk of fish being killed as a result of insecticide being introduced into lakes or water courses through surface runoff, and reduces insecticide exposure of those applying and which could enter the treated field with crops shortly after spraying and reduce the amount of residue that could remain on the harvested crops. Moreover, any residues of sigma-cypermethrin that may remain on harvested crops could be expected to be significantly less toxic than the residues of cypermethrin administered to achieve the same level of protection against insect-infesting crops, and cypermethrin already alone, for crop-borne insecticide, shows relatively low toxicity to mammals.

Claims (7)

PATENT APPLICATIONS A compound characterized in that it is a mixture of lS-eis-S, lR-cis-S, lS-trans-S and lR-trans-S isomers of cypermethrin. Compound according to claim 1, characterized in that the isomer concentrations are approximately the same. Compound according to claim 2, characterized in that it contains at least 88% of the total cypermethrin isomers and at least 80% of the cypermethrin S isomers. Compound according to claim 3, characterized in that the cis / trans ratio is in the range 45/55 to 55/45. 5. Racemic cis / trans 3- (2,2-dichloroethenyl) -2,2-dimethylcyclopropane carboxylic acid conversion product as chloride with (S) (cyano) (3-phenoxyphenyl) methanol. Composition comprising the compound of claims 1, 2, 3 or 4 in admixture with one or more agriculturally acceptable adjuvants. An insect control method, characterized in that an insecticidally effective amount of the composition of claim 6 is applied to the insect or to the site where the insect is expected.