Resistance to the organophosphate chlorpyrifos ethyl was investigated in greenhouse populations of Trialeurodes vaporariorum from Turkey using both bioassay and biochemical studies. These populations were collected from Antalya, Izmir, and Mersin. LC50 values to chlorpyrifos ethyl were determined for all populations using leaf dip bioassay. Resistance ratios (RRs) were calculated from these LC50 values relative to the susceptible BCP population. Bioassay results from all populations revealed varying levels of resistance to chlorpyrifos ethyl with resistance ratios between 7.16- and 12.89-fold in the greenhouse whitefly populations from Turkey. Results revealed the first documented cases of insecticide resistance in this species in Turkey.
Biochemical assays on acetylcholinesterase (AChE) sensitivity in individual greenhouse whitefly were conducted to explore the role of this enzyme in conferring resistance to this insecticide. AChE insensitivity in individual greenhouse whitefly was determined. This is believed to be the first record of sensitive and insensitive AChE variants to be identified according to their sensitivities to chlorpyrifos ethyl-oxon and pirimicarb