Biocontrol of agricultural pests based on autodissemination of entomopathogenic nematodes of Steinermatidae family (Nematoda: Rhabditida)

At present, the development of biological plant protection systems is among the most important economic, social and environmental challenges. Creating an effective system is impossible without the combination of a variety of biological agents and pest control techniques. Combining a variety of pathogenic organisms and synthetic sex pheromones is a way to improve the situation. This paper shows the effectiveness of entomopathogenic nematodes (EPN) of the family Steinernematidae Filipjev, 1934 as an autodissemination agent for agro-ecosystems under crop rotation and at apple-tree orchard, and assessed the effect of introducing pathogens on indigenous entomopathogens in soil. In particular, a decrease in the number of harmful insects and an increase in the activity of natural beneficial entomopathogens have been demonstrated. The essence of the method consists in the targeted introduction of entomopathogenic bioagents into the agro-ecocenosis by means of their application to attracted insects caught in traps, and thus creating an epizootic in the populations of target species. Previously, entomopathogenic nematodes were not used as autodissemination agents against superdominant species, the codling moth Cydia pomonella L., 1758 and click beetles of the family Elateridae Leach, 1815; moreover, their effect on other members of the entomofauna of agro-ecocenoses has not been studied either. The purpose of this work was to evaluate the effectiveness of the EPN autodissemination method for various cultures. The successful testing of Granulosis virus dissemination method in the apple orchard and the EPN autodissemination against wireworms prompted us to conduct the investigation reported herein. Two species of entomopathogenic nematodes of Steinernematidae family, the Steinernema carpocapsae (Weiser, 1955) and St. feltiae (Filipiev, 1934) were reproduced in lab culture in different host insects to produce nematode inoculums. The experiments found out that specially designed formulations and modified pheromone traps ensure EPN introduction into the agrocenoses due to nematode invasion of trapped insects followed by their free flight to spread pathogens. As a result, the nematode-bacteria complex occurred in 60.0-100 % of click beetles of the Elateridae family and 34.0-35.3 % of C. pomonella L. and Grapholitha molesta (Busck, 1916). This indicates accumulation of biocontrol agents in the soil of the agrocenoses due to EPN introduction. The EPN autodissemination application also reduced the damage to apple fruits by up to 10 %, and corn and soybean plants by 13,2 % compared to areas where chemical treatments were applied. The method has no negative impact of EPN on green lacewings ( Chrysopidae Schneider, 1851) and the Hymenoptera of the families Braconidae , Latreille, 1829 and Ichneumonidae , Latreille, 1802, the predators of insect pests. In the garden where the tests were carried out, there was a 15 % increase in infection of caterpillars of C. pomonella by Hymenoptera . It is established that the EPN autodissemination stimulates the activity of indigenous soil EPN, leading to a 1.5-2.0-fold increase in the number of trapped nematodes in the bioassay test compared to the period prior to EPN autodissemination. Importantly, the effect of autodissemination turned out to be prolonged and manifested the next year both in the apple orchard and in the crop rotation of agricultural crops.