Survey of the presence of Biological Control Agents in Piedmont chestnut groves: focus on entomopathogenic nematodes

In Europe, chestnut cultivation is threatened by phytophagous insects that cause early fruit drops and subsequent significant losses of harvested products. Tortrix moths (Cydia fagiglandana, C. splendana, Pammene fasciana) and chestnut weevils (Curculio elephas e Curculio propinquus) are considered among the most harmful native species. In order to implement conservation biological control strategies, the study and monitoring of biological control agent communities are essential to assess the ecosystem's ability to respond to pressures exerted by phytophagous populations. In this study, soil microbial communities — including entomopathogenic bacteria, fungi and nematodes — were characterized in two different chestnut-growing environments (a fruit-producing chestnut orchard and a mixed forest with chestnut presence) across two distinct seasons (autumn and spring) over two consecutive years. Among the entomopathogenic nematodes, morphological and molecular analyses identified the presence of Steinernema feltiae, S. carpocapsae, S. affine and two undescribed Steinernema spp. currently under taxonomic investigation. S. feltiae was found to be the most frequent species. Analysis of community-level data showed differences among different chestnut environments, suggesting a potential influence of chestnut management on the abundance and distribution of nematode species in the soil.