Pathogenic post-effect of entomopathogenic fungi on phytophagous pests and entomophagous biocontrol agents

All-Russian Institute of Plant Protection, sh. Podbelskogo 3, St. Petersburg, Pushkin 196608 Russia

^* Corresponding author: vapavlyushin@vizr.spb.ru

Abstract

Phytosanitary optimization of agricultural ecosystems under conditions of glasshouses and organic farming urgently demands guaranteed effect of plant protection. This can be achieved only through effective exploitation of a complex of biological agents, including arthropod predators and parasites, entomopathogenic fungi, nematodes and other microbes. Entomopathogenic fungi Beauveria bassiana and Lecanicillium muscarium are characterized by facultative parasitism and possess high potential to control phytophagous insects, including pests of vegetable crops in glasshouses. In aphids, fungal pathogenesis was found to be comprised of primary mycosis and toxigenic post-effect in a row of consequent generations. For example, L. muscarium and B. bassiana had an adverse effect on fertility and survival rates of females of aphids Aphis gossypii up to the fifth generation. The longevity, reproductive period and amount of progeny were decreased in aphids treated with water suspension of fungal conidia. It can be deduced that the post-effect is caused by toxic action of metabolites as no evident mycosis was observed in the experiments. Similar type of after-effect is observed in the lacewing Chrysopa carnea contaminated with fungal conidia. The effect is also toxigenic being most prominent in the first generation of the survivors’ progeny and traceable up to the fifth generation. The consequences of the infection are best seen in the rate adult emergence which is twice as low as compared to control. This knowledge is essential to avoid antagonism between different groups of natural enemies exploited in biological control and to design adequate technology for their application.