Lethal and sublethal effect of piryproxyfen and hexaflumoron on Phthorimaea operculella Zeller (Lep: Gelechiidae)

The potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae), is one of the most important pests of potato, Solanum tuberosum L., in both fields and stores at tropical and subtropical regions of the world. In current research, the susceptibility of some developmental stages of the pest to the insecticides, piryproxyfen and hexafumoron was investigated by using two methods, dipping and contact methods. The effects of sublethal concentrations of insecticides were studied on life table parameters such as life expectancy, survival rate, adult longevity, fecundity, sex ratio and stable population growth parameters such as gross reproduction rate, net reproduction rate, intrinsic rate of increase, finite rate of increase and mean generation time under controlled conditions (25 ± 2 °C, 65 ± 5% RH and 16L:8D h). The LC50 values of piryproxyfen and hexaflumoron on egg and first instar larvae were 3500, 3240 and 5200, 3450 ppm respevtively. Insecticides that were treated even with higher than farm application dose but no significant effects were observed. Insecticide concentration up to 5000 ppm did not result in considerable mortality on adults. According to the results, piryproxyfen showed high toxicity on egg. Most stable population parameters of P. operculella such as gross and net reproductive rates, intrinsic and finite rate of increase and generation time as well as biological parameters such as fecundity, fertility and longevity were affected by the insecticides. Piryproxyfen and hexaflumoron decreased fecundity, hatchability, the net reproductive rate, intrinsic rate of increase, finite rate of increase, gross reproduction rate and mean generation time of P. operculella. Thus we could use these insecticides against the pest If similar results are obtained for these chemicals in the field.