Effects of selected insecticides on osmotically treated entomopathogenic nematodes

Combining environmentally friendly insecticides with entomopathogenic nematodes may constitute an effective alternative to conventional chemical control of many insect pests. The objective of this laboratory study was to evaluate the effects of selected insecticides which are commonly used for pest control in vegetables in China on osmotically treated and untreated infective juveniles of Steinernema carpocapsae strain All. The insecticides azadirachtin, chlorpyrifos, cypermethrin, fipronil, imidacloprid, malathion, thiamethoxam and chlorantraniliprole-thiamethoxam had no adverse effects on nematode survival and infectivity. In contrast, bisultap, emamectin benzoate, phoxim and rotenone proved harmful to S. carpocapsae All mainly by reducing infectivity of the infective juveniles to larvae of the greater wax moth, Galleria mellonella. Osmotic induction is a promising way to induce entomopathogenic nematodes into partial anhydrobiosis and thus increase environmental stress tolerance of the nematodes as well as their shelf life after production. The present results showed that osmotic treatment did not adversely affect fitness of the nematode in terms of its susceptibility to insecticides and even increased its tolerance to chlorpyrifos and rotenone. The results of this laboratory study indicate that several of the tested insecticides can be safely combined with S. carpocapsae All within an integrated pest management approach.