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Effect of Synergists on Organophosphate and Permethrin Resistance in Sweetpotato Whitefly (Homoptera: Aleyrodidae)

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A field strain of Bemisia tabaci (Gennadius) from California, resistant to malathion, methyl parathion, sulprofos, permethrin, and DDT, showed increases in resistance levels (ranging from 1.1- to 8.9-fold) in a subsequent survey. Selective synergists were used to study the involvement of hydrolytic or oxidative enzymes (or both) in the resistance mechanism of the resistant strain. Resistance levels were decreased markedly when DEF (S,S,S-tributyl phosphorotrithioate) synergized three organophosphate (OP) compounds (malathion, methyl parathion, and sulprofos) and one pyrethroid (permethrin), suggesting the involvement of increased detoxication by est erases as part of the resistance mechanism. In addition, malathion was synergized by triphenyl phosphate (TPP), indicating the influence of carboxylesterases in malathion resistance. No highly active est erases were associated with oregano phosphate (OP) resistance. Piperonyl but oxide (PB) synergized the three OP5, permethrin, and DDT to different degrees in both susceptible and resistant strains, thus indicating the importance of enhanced oxidative metabolism in B. tabaci resistance. Because use of DEF, PB, and TPP did not increase the toxicity in the resistant strain to that of the susceptible strain, an unidentified resistance factor, possibly insensitive acetylcholinesterase, may be of importance in OP resistance. DEF antagonized DDT toxicity in the resistant strain, which increased the resistance ratio from 12.0- to 16.7-fold. DDT was synergized to a limited extent by diethyl maleate (DEM), thus suggesting limited metabolism by DDT-dehydrochlorinase in the resistant strain. A non metabolic knockdown resistance mechanism (kdr) may be a factor in DDT resistance because neither PB nor DEM supressed resistance completely.

Document Type: Research Article

Publication date: February 1, 1988

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  • Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.
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