Fourth International Bemisia Workshop International Whitefly Genomics Workshop
Reversal of Resistance to Pyriproxyfen in the Q Biotype of Bemisia tabaci (Hemiptera: Aleyrodidae)
1 Department of Entomology, the Hebrew University of Jerusalem, Faculty of Agricultural, Food and Environmental Quality Sciences, Rehovot, Israel.
2 Department of Entomology, Agricultural Research Organization, The Gilat Research Center, Israel
Pyriproxyfen, a juvenile hormone (JH) mimic, is a biorational insecticide that disrupts insect development. It is one of the principal insecticides being used to control Bemisia tabaci (Gennadius) on cotton, and has many environmentally positive attributes, which makes it compatible with integrated pest management (IPM) programs. In Israel, high levels of resistance to pyriproxyfen have been observed in several isolated regions. Here, we tested whether temporal refuges from exposure to pyriproxyfen can be useful for restoring the effectiveness of the compound. We found an eight-fold reduction in resistance when exposure to pyriproxyfen was ceased for 13 generations. Reversal of resistance was accompanied by increased biotic fitness of the revertant colony. By incorporating experimental estimates of nymph survival, sex ratio, fecundity, egg-hatching rate and developmental time, the seasonal cost per generation for resistant insects was estimated to be 25%. A genetic simulation model, optimized by empirical data from bioassays, predicted fitness cost per generation of 19% for resistant homozygous (RR) females and hemizygous (R) males, and produced rates of reversal similar to the experimental results. The model also predicted that even after five years (~55 generations) without pyriproxyfen treatments, the frequency of the resistance allele (R) will still remain high (0.02). We therefore conclude, based on experimental and modeling results, that the effectiveness of temporal refuges for reversing development of resistance to pyriproxyfen in B. tabaci may be limited.
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