Synergism of permethrin by formamidines in resistant and susceptible strains of Heliothis virescens: A comparison of chlordimeform, amitraz, and a metabolite
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PublisherThe University of Arizona.
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AbstractLaboratory tests conducted to evaluate the ability of three formamidines (chlordimeform, amitraz, and N'-(2,4-dimethylphenyl)- N-methylformamidine SN-49844, a metabolite of amitraz) to synergize permethrin in tobacco budworm (TBW) showed no synergism in susceptible larvae, but did show synergism in resistant larvae. Chlordimeform (CDF) and N'-(2,4-dimethylphenyl)-N-methylformamidine SN-49844 showed higher degrees of synergism than amitraz. Selection of cross-bred larvae of tobacco budworm using permethrin ± formamidine mixtures at LD 80 for four generations produced strong tolerance to all agents used in the selection. A test for cross-resistance to cypermethrin and to methyl parathion in a permethrin-selected strain of tobacco budworm showed resistance levels of 58-fold, and 48-fold, respectively, compared with susceptible TBW.