Selection, resistance risk assessment, and reversion toward susceptibility of pyriproxyfen in Musca domestica L.

Pyriproxyfen, a juvenile hormone mimic, is an effective larvicide against many pests of veterinary and public health importance. Pyriproxyfen is a biorational insecticide having many environmentally friendly attributes that make it compatible with integrated pest management programs. This experiment was performed for the assessment of resistance evolution and reversion toward susceptibility of Musca domestica to pyriproxyfen. Repeated selection at successive generations resulted in 5.09- and 130-fold increase in lethal concentration 50 (LC50) compared to field and susceptible strain, respectively. A significant decline after 22 generations without selection suggesting resistance to pyriproxyfen was unstable in M. domestica. Realized heritability (h (2)) of resistance to pyriproxyfen was 0.035 in pyriproxyfen-selected strain of M. domestica. The projected rate of resistance development indicated that, if slope = 1.28 and h (2) = 0.035, then 46-21 generations are required for 10-fold increase in LC50 at 50-90 % selection intensity. These findings suggest that a risk for resistance development to pyriproxyfen occurred in M. domestica under continuous selection pressure. Pyriproxyfen susceptibility reversed when its application is ceased for a specified duration.