METHOD FOR CONTROL OF SOIL-BORNE INSECTS

Abstract: A method for controlling soil-borne insects such as southern corn rootworm and exemplified in which a pyrethroid selected from mono- and di-fluorophenylmethyl 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-diemethylcyclopropanecarbo xylates is applied to the soil for insect control.

Description: METHOD FOR CONTROL OF SOIL-BORNE INSECTS This invention pertains to the general field of insecticides and relates particularly to a method for controlling soil-borne insects, especially those insects, such as southern corn rootworm, which spend a major portion of their larval life in the soil, i.e., soil-borne insects, by applying to the soil certain fluorinated phenylmethyl esters of 3-(2-chloro-3,3,3- trifluoro-l-propenyl)-2,2-dimeth lcyclopropanecar- boxylic acid. U.S. Patent 4,332,815 discloses a broad class of perhaloalkylvinylcyclopropanecarboxylates described as having excellent insecticidal activity against Lepidoptera and Homoptera. The patent illustrates that these compounds have superior contact and foliar activity, but is silent as to any activity these com¬ pounds may have against soil-borne insects. European Patent Application, publication number 10879 Al, , discloses certain fluorinated phenylmethyl esters, especially tetrahalophenyl and pentahalo- phenyl, of perhaloalkylvinylcyclopropanecarboxylic acids as "fumigant insecticides." The application discloses the use of the compounds for control of soil insects and demonstrates efficacy of tetrahalophenyl- methyl and pentahalophenylmethyl compounds. However, the data reported for the mono- or difluorophenyl- methyl compounds of the present invention show these compounds essentially inactive against Diabrotica balteata, a rootworm which spends its larval life in soil. While U.S. Serial No. 589,622, filed March 14, 1984, discloses the use of 2,4,6-trifluorophenylmethyl 3-(2-chloro-3,3,3-trifluoro-1-propenyl)-2,2-dimethyl- cyclopropanecarboxylate for the control of soil-borne insects, that disclosure taken with the disclosure of the European Patent Application noted above would not suggest to one skilled in the art the significantly greater activity against soil-borne insects of the mono- or difluorophenylmethyl esters of the present invention. It has now been found that certain cis-3-(2- chloro-3,3,3-trifluoro-l-propenyl)-2,2-dimethylcyclo- propanecarboxylates, especially the 2-fluorophenyl¬ methyl and 2,6-difluorophenylmethyl esters, compounds encompassed by the claims in U.S. Patent 4,332,815 and specifically exemplified in the European Patent Appli¬ cation noted above, exhibit surprising activity against soil-borne insects such as southern corn rootworm (Diabrotica undecimpunctata howardi). In accordance with the foregoing, this invention provides a method for controlling soil-borne insects which comprises applying to the soil in which plants • are or are about to be planted from about 0.2 to about 8 parts by weight of one or more compounds of this invention, especially 2-fluorophenylmethyl or 2,6-di- fluorophenylmethyl 3-(2-chloro-3,3,3-trifluoro-1-pro- penyl)-2,2-dimethylcyclopropanecarboxylate, per million parts by weight of soil. These compounds have the general structure shown in formula I, where n = 1 or 2. The compounds employed in this invention and cer¬ tain intermediates therefore exist as cis and trans geometrical isomers, the carboxy and the substituted vinyl groups at the 1- and 3-positions of the cyclo- propane ring are either cis or trans with respect to each other. Preparation of such compounds will usually yield a mixture of cis and trans isomers, designated cis,trans, in which the ratio of cis to trans may vary over a wide range. Since positions 1 and 3 of the cyclopropane ring are asymmetric carbon atoms, there are also 4 optical isomers which may be designated 1R, cis; IS, cis; 1R, trans; and IS, trans. The compounds of this invention may also exist as E or Z isomers or as mixtures of E and Z isomers, designated E, Z, depending on the spatial relationship of substituents on the -carbon of the vinyl group to those on the β-carbon of the vinyl group. In the cyclopropanecarboxylate art it is known there may be substantial differences in the level of insecticidal activity between the cis and trans isomers. As between the cis and trans isomer of a given synthetic cyclopropanecarboxylate, the cis isomer is often, though not always, more active than the trans and also more active than the cis,trans mixture. Similar differences in activity may also occur with respect to the E and Z isomers. Unless a contrary intent is expressed, the inven¬ tion embodies and includes all compounds in which the carboxy and substituted vinyl groups at the 1- and 3-positions of the cyclopropane ring are cis or trans, or a mixture of cis and trans configuration with respect to each other; the cis isomers, particularly the lR,cis isomers are generally preferred. Similarly, the individual E and Z isomers, as well as the mixtures, are also contemplated by and within the scope of the present invention. The compounds may be prepared by various methods known to those skilled in the art including those described in U.S. Patent 4,332,815, incorporated here¬ in by reference. A convenient method for preparing the compounds is from a compound of formula II in which R is hydroxy, lower alkoxy, or halogen, by reaction with a compound containing a 2-fluorobenzyl or 2,6-difluorobenzyl alcohol residue, for example, by reaction with the alcohol itself when II is the acid chloride. The compound 2-fluorophenylmethyl cis-3-(2-chloro- 3,3,3-trifluoro-l-propenyl)-2,2-dimethylcyclopropane- carboxylate (Compound A) was obtained as an oil. The nmr spectrum was consistent with the assigned structure: δ(CDCl 3 , TMS) 1.32 (s, 6H) , 2.08 (t, 2H) , 5.21 (s, 2H), 6.83-7.63 (m, 5H) . Analysis calc'd for c χ6 H 15 C1F 4 0 2 : C 5 - 81 » H 4 - 28 Found: C 55.06, H 4.53 The compound 2,6-difluorophenylmethyl cis-3-(2- chloro-3,3,3-trifluoro-l-propenyl)-2,2-dime h lcyclo- propanecarboxylate (Compound B) was obtained as an oil. The nmr spectrum was consistent with the assigned structure: (CDCI3, ™ s) l ' 2 8 <- s ' 6H) » 2 ' 04 ( ' 2H) > 5.24 (s, 2H), 6.73-7.56 (m, 4H) . Analysis calc'd for c 6 H i4 Clf; 5 0 2 : C 52 « 12 5 H 3 - 83 Found: C 52.76; H 4.10. In the method of this invention the active com¬ pound is applied by incorporating a formulation there¬ of into the soil in which agricultural crops have been or will be planted, that is, the locus of infesta- tion. This may be achieved by broadcasting the formu¬ lation over the planted area or the area to be planted or by banding the application in the root zone where plants have been or are to be planted. It will be readily apparent where the latter method is employed that an amount of formulation sufficient to supply an insecticidally effective concentration of active ingredient in the soil must be applied to the root zone. A suitable use rate for this purpose is in the range of 0.1 to about 5 kg/ha of active ingredient, preferably 0.2 to 1.5 kg/ha. Typical formulations for use in the method υf the invention include the active ingredient in combination with an agriculturally acceptable carrier or extender, preferably with a surface active agent, and optionally with other active ingredients. Suitable formulations include granules of various sizes, dusts, wettable powders, emulsifiable concentrates, solutions, disper¬ sions, and the like, with the choice depending upon the environmental factors at the situs of infestation and the method of application selected. A typical formulation may vary widely in concentration of the active ingredient depending upon the additives and carriers used and the desired mode of application. Thus active ingredient may be present at a concen- tration of 0.1% to 99.5% by weight of the formula- tion. An agriculturally acceptable carrier may com¬ prise about 99.5% by weight to as low as 0.5% by weight of the formulation. Compatible surface active agents, if employed in the formulation, may be present at various concentrations, suitably in the range of 1% to 30% by weight of the formulation. The formulation may be used as such or diluted to a desired use dilution with a diluent or carrier suit¬ able for facilitating dispersion of the active ingre- dient. The concentration of the active ingredient in dilution for the application may be in the range of about 0.0001 to about 10% by weight, with lower con¬ centrations particularly useful when the diluent is water. The compounds of the invention were subjected to a filter paper test and also were incorporated in soil and tested for activity against third instar southern corn rootworm larvae by the general method of G. R. Sutter, J. Econ. Entom. , Vol 75(3), 4 * 89-91 (1982), incorporated herein by reference. EXAMPLE 1 Filter Paper Test In the filter paper test a compound of the inven¬ tion was dissolved in acetone/water to give a test solution containing the specified concentration of test chemical. A 100 mm diameter filter paper was placed in a disposable, plastic, 100 mm x 15 mm petri dish and 2.5 ml of the test solution was poured onto the filter paper. After excess water had evaporated (1 - 1.5 hours), ten 3rd or 4th instar larvae were placed on the damp filter paper and the petri dish was covered. Two replicates of the test were carried out for each compound. Twenty-four hours after infesta¬ tion the dead and moribund larvae were counted, and percent kill was determined. Results are reported in Table 1. TABLE 1 Filter Paper Test at 1 ppm Percent Kill Phenyl Compound No. SUR 3 BUB b Substitution A 90 100 2F B 100 100 2F, 6F C 90 95 3F D 65 30 4F E 100 100 2F, 4F F 100 100 2F, 5F G 95 100 3F, 4F H C 95 100 2F, 4F, 6F a Southern corn rootworm (Diabrotica undecimpunctata howardi) b Banded cucumber beetle (Diabrotica balteata) c Compound H is 2,4,6-trifluorophenylmethyl cis-3- (2-chloro-3,3,3-tri luoro-l-propenyl)-2,2-di- methylcyclopropanecarboxylate, the compound of U.S.S.N. 589,622, filed March 14, 1984. Table 1 shows that at the low concentration of 1 part per million the compounds of this invention are effective in killing the larvae of two different insect species that spend their larval life in the soil. These results are particularly unexpected in view of the lack of activity against one of these species reported in European Patent Application, publication number 10879 Al, at substantially higher concentrations. Soil Incorporation Test A stock solution of each test compound was pre¬ pared by dissolving 4.8 mg in 10 ml of acetone and diluting with 90 ml of acetone/water (1:9). The addi¬ tion of -5 ml of this stock solution to 30 g of air- dried, clay loam soil in a 3-oz plastic cup provided a concentration of 8 ppm of the test compound in the soil. Serial dilution of the stock solution was used to obtain concentrations of the test compound in soil of 4, 2, 1, 0.5, 0.25, and 0.125 ppm. In all cases 5 ml of a solution having the required concentration was added to 30 g of soil. The treated soil was allowed to stand uncovered in a hood for 0.5 hour to evaporate the acetone. Before infesting the soil with southern corn rootworm larvae, the soil was mixed thoroughly. Two three-day-old corn sprouts and ten early third-stage (9-10 days old) southern corn root- worm larvae were placed in the cup which was then covered with a plastic lid, and held in a closed plastic bag. After storage at 74-78°F for 48 hours, the mortality of the larvae was determined by removing the cup from the plastic bag, removing the cover, and placing the contents of each cup in a modified Berlese polyethylene funnel fitted with an 18-mesh screen. The funnels were placed over containers of an aqueous detergent solution. Incandescent lights (100 watts) were placed 36 cm above the soil samples. The heat from these lights slowly dried the soil which caused larvae that had not been affected by the test compound to emerge from the soil and drop into the detergent solution. Larvae that did not emerge were judged to be dead. The percent mortality was determined in this manner for each concentration. Duplicate tests were run at each concentration. Since the results of the soil incorporation test may differ somewhat from day to day owing to factors which cannot be controlled, e.g. the precise develop- ment and state of health of the larvae used in the test, a reference compound effective against soil insects is included in each soil incorporation test, as is a blank with insects, but no active ingredient. The raw data for each compound is put into a computer programmed to correct for the blank and calculate the LC- Λ for that compound in that test run. The com- pounds tested can then be compared with the reference standard in the same test run and a relative potency determined. Relative potency (RP) is defined as LC Reference Compound/LC-. Q Test Compound. In this manner compounds evaluated at different times may be more accurately compared. Table 2 demonstrates the effi- cacy of certain compounds of this invention and also illustrates determination of relative potency. Results of the tests recorded in Table 2 show that Compounds A and B each show an unexpectedly high ini¬ tial level of activity against southern corn rootworm, and each is signi icantly more effective against the southern corn rootworm than is the trifluoro analog of the prior art. TABLE 2 Insecticidal Activity of Fluorophenylmethyl cis-3-(2-chloro-5, 3, 3-tri luoro-1-propenyl) - 2 , 2-dimethylcyclopropanecarboxylates in the Soil Against the Southern Corn Rootworm Rate of , Application Percent Ki 11 Cpd A Ref • * Cpd. B Ref • Cpd. H Ref. 4.0 ppm 100 - 95 - 100 - 2.0 85 90 95 100 85 85 1.0 75 80 90 95 • 85 ' 75 0.5 70 75 85 60 70 70 0.25 65 45 65 40 25 40 0.125 - 35 - 10 - 35 LC 50 Cppm) 27 • 38 • 14 • 45 • 4 .3 RP 1. 4 1 3. 2 1 0. 75 1 *The reference compound is ( 2-methyl [ 1, 1 ■ -biphenyl ]-3- yl)methyl cis-3-(2-chloro-3, 3,3-trifluoro-l-pro- penyl)-2, 2-dimethylc clopropanecarboxylate. The relative potencies of the mono- and difluoro- phenylmethyl esters of this invention are presented in Table 3. TABLE 3 Relative Potencies in Soil . Incorporation Test Relative Potency Compound vs. SCR* in Soil 0 A 1.5 B 3.4 B 1 2.05 C 1.08 D 1 E 0.78 F 0.72 G 0.62 H 0.75 Reference Compound 1 a Diabrotica undecimpunctata . ' howardi b In B' the cis/trans ratio o: £ 3-(2-chloro-3,3,3- trif1uoro-1-propenyl)-2,2-dimethylcyclopropane- carboxylates is 75/25. B contains more than 98% of the cis isomer. Other soil-borne insects that may be controlled by the compounds of the invention include: Japanese beetle (Popillia japonica Newman) , black cutworm (Agrotis ipsilon) , Oregon wireworm (Melanotus oregonensis) , corn wireworm (Melanotus communis) , Gulf wireworm (Conoderus amplicollis) , southern potato wireworm (Conoderus falli), and Prairie grain wireworm (Ctenicera aeripenni destructor) .

Claims: Claims: 1. A method for controlling soil-borne insects which comprises applying to the soil in which plants are or are to be planted an insecticidally effective amount of one or more compound selected from the group consisting of mono- and difluorophenylmethyl 3-(2- chloro-3,3,3-trifluoro-1-propen 1)-2,2-dimeth lcyclo- propanecarboxylates. 2. A method of claim 1 characterized in that the carboxylate is an ester of a fluorophenylmethyl alcohol or of 2,6-difluorophenylmethyl alcohol. 3. The method of claim 2 characterized in that the compound is 2-fluorophenylmethyl 3-(2-chloro- 3,3,3-trifluoro-l-propenyl)-2,2-dimethylcyclopropane- carboxylate. 4. The method of claim 1 characterized in that the active ingredient is 2,6-difluorophenylmethyl 3-(2-chloro-3,3,3-trifluoro-l-propenyl)-2,2-dimeth 1- cyclopropanecarboxylate. 5. The method of claim 1 characterized in that there is employed the predominantly cis or predomi¬ nantly lR,cis isomers of the active ingredient or mixtures thereof. 6. The method of claim 1 characterized in that an active ingredient is applied at a rate of 0.1 to 5 kg/ha.

Inventors: CULLEN THOMAS GERARD, PHILLIPS RICHARD BENTON, CULLEN, THOMAS, GERARD, PHILLIPS, RICHARD, BENTON
Applicants: FMC CORP, FMC CORPORATION
Application year: 1985
Main classification: A01N53
IPC codes: A01N53