Effect of entomopathogenic nematodes on soil arthropod diversity in pistachio orchards

Pistachio growers apply entomopathogenic nematodes of the species Steinernema carpocapsae to control overwintering navel orangeworm, Amyelois transitella. Applied at a rate of 25/cm² under trees, these nematodes represent a large resource subsidy into the soil ecosystem. We hypothesize that such a subsidy will alter local soil faunal diversity. Entomopathogenic nematodes may negatively affect soil fauna through direct parasitism or their bacteria may produce toxic or repellent chemicals. Additionally, nematophagous mites and collembolans may respond positively to the subsidy. In this study, we compared invertebrate diversity under 35 treated and 35 control trees one week after entomopathogenic nematode application.