November 1951 E-828 United States Department of Agriculture Agricultural Research Administration Bureau of Entomology and Plant Quarantine PRELIMINARY TESTS WITH CERTAIN N-SUBSTITUTED BENZAMHES FOR SYNERGISTIC ACTION IN PYRETHRUM FLY SPRAYS By Norman Mitlin and S. I. Gertler, Division of Insecticide Investigations, and W. A. Gersdorff , Division of Stored Product Insect Investigations In a previous publication in this series (E-8o5) the authors re- ported that certain N-substituted benzene sulfonamides had been found to show promise as synergists for pyre thrum in fly sprays. Further studies have now shown that several N-substituted benzamides also act as pyreth- rum synergists. These compounds are characterized by the general formula 0 (I C6H5-C-N-N /R R' R may be either hydrogen or an alkyl group, and R» may be hydrogen, an alkyl, or a cyclic group. These groups may be either substituted or un- substituted. The compounds were generally prepared by reacting benzoyl chloride with an amide under suitable conditions. The compounds were incorporated in sprays alone and in mixtures with 1 mg. of pyrethrins per milliliter. Since their solubility in refined kerosene was low, an equal amount of acetone was used as an auxiliary solvent. Varying concentrations of the adjuncts were used. Pyrethrum standards, in which pyrethrin I and cinerin I comprised 5U percent of the total pyrethrins, were also prepared in the same solvent mixture at concentrations of 1 and 2 mg. per milliliter. The tests were made by the Campbell turntable method on adult house flies (Musca domestica L. ) reared by standard laboratory procedure. Since knockdown is increased by the addition of acetone, it was not eF timated. Mortality only was determined for each spray. Approximately 100 flies averaging 3 days of age v/ere used in each test. The mixed sprays were replicated four times, the sprays containing the adjunct alone but twice. Since it was necessary to make the tests in a number of different series, the two standard pyre thrum sprays were included in each series as a base of reference. - 2 - To avoid reporting many series and to put the results on a com- parable basis, the following procedure "was followed: The mortalities obtained for the standard sprays in each series were plotted on log- probability paper and straight lines drawn. From these lines the py- rethrins equivalent was estimated for each mixed spray. These figures may be considered as expressions of relative toxicity, since they are all compared with the concentration of 1 mg. of pyrethrins per milli- liter. These results are assembled in table 1. At the concentrations used, the adjuncts alone caused negligible mortality. For 11 of the mixtures the increase in toxicity was signifi- cant. Synergism was therefore shown in these mixtures. The effective adjuncts were as follovfs: N , K-Dicy clohexylbenzamide N,N-Diisopropylbenzamide N, N-Dipropylbenzamide N-Isopropylbenzamide N- (l-Methylamyl )benzamide N-Benzylbenzanilide 2 ' -Bromobenzanilide 2,-Chlorobenzanilide 2 » ,$ ' -Dichlorobenzanilide o-Benzanisidide o-Benzophenetitide In mixtures containing the following adjuncts the increase in tox- icity was at the borderline of significance: N,N-Diethylbensamide, N-propylbenzamide, and 9-benzoylcarbazole . - 3 - Table 1. — Toxicity to house flies of space sprays containing certain benzamides in mixtures with 1 mg. of pyrethrins per milliliter Material Concentration Mg./ml. Fyrethrins equivalent of mixture fyrethrins equivalent required to show synergism Benzamide 10 0.81* 1.51* Benzamide, N-benzoxy- 10 .81 1.35 N-sec-butyl- 20 1.15 1.38 N , N-dicyclohexyl- 20 2.15 1.39 N,N-diethyl- 20 1.1*7 1.51 N, N-di ( 2-ethylhexyl)- 20 >2 - N,I\f-diisopropyl- 20 1.81* 1.38 N,N-dimethyl- 20 1.05 1.38 N,N-dipropyl- 20 2 - N-ethyl- 20 1.09 1.51 N-isopropyl- 20 1.59 1.38 N- ( 1-methylamyl ) - 20 1.81* 1.35 N-propyl- 20 1.1*6 1.51 Benzanilide ,N-benzyl- 20 1.71 1.39 2'-bromo- 20 >2 1.36 3 • -bromo- 20 1.07 1.30 k ' -bromo- 10 .99 1.30 2 • -chloro- 20 1.7U 1.51* 3 ' -chloro- 20 1.10 1.51* 1* • -chloro- 10 .80 1.36 2>,5'-dichloro- 10 1.66 1.39 N-1-naphthyl- 10 .83 - N-2-naphthyl- 10 .50 - 3 ' -nitro- 20 .81 1.30 l*'-nitro- 10 .86 1.30 N-phenyl- 10 .51 - 2 ' -phenyl- 5 .61; — o-Benzanisidide 20 1.90 1.35 Benzoic acid, p-benzamido, ethyl ester 20 .86 1.30 o-Benzophenetitide 20 3.01* 1.35 p-Benzophenetitide 20 1.20 1.39 Carbazole , 9-benzoyl- 20 1.29 1.30 icitv (IF FLORIDA « i liiuhP1