LAUSR

The whitefly Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) cryptic species has become an important pest of cotton and vegetable crops in Egypt. In this study, resistance to three organophosphate insecticides (OPs), chlorpyrifos-methyl, profenofos and pirimiphos-methyl, and detoxification enzymatic activities of acetylcholinesterase, carboxylesterase, and monooxygenase were evaluated to establish baseline resistance levels for B. tabaci infesting cotton in seven Egyptian governorates, compared to a susceptible laboratory reference B. tabaci colony. Resistance to OPs ranged from low-to-moderate or low-to-high, while detoxification enzymatic activities were predominantly governorate-dependent. Phylogenetic analysis of a fragment of the mitochondria cytochrome oxidase I gene (756 bp) identified field-collected B. tabaci as the B mitotype. The results provide baseline OP resistance levels for B. tabaci that will aid in interpreting future monitoring outcomes and enable detection of insecticide resistance fluxes.