The risk of bionematicide seed treatments to entomopathogenic nematodes used in corn rootworm, Diabrotica spp. management

Corn rootworm (CRW; Diabrotica spp. (Coleoptera: Chrysomelidae)) is a major concern for North American corn (Zea mays L.) growers. Entomopathogenic nematodes (EPNs) have become an appealing biological control method due to the recent rise in resistance to Bacillus thuringiensis (Bt) toxins produced in transgenic corn. EPNs parasitize CRW to diminish larval populations and adult emergence. Since beneficial nematodes aren’t analyzed as a non-target pest during the registration of biological nematicide seed treatments, the impact of these bionematicides on EPNs was brought into question. It was hypothesized that bionematicide seed treatments would not negatively impact EPN presence in the soil or their ability to control CRW. The objective of this research was to evaluate the ability of Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora to control CRW in the presence of corn treated with four commercially available Bacillus-based bionematicides. In 2024, controlled greenhouse experiments were conducted to simulate field exposure, as well as a direct exposure experiment to determine mortality and EPN ability to parasitize a host following exposure. Due to the beneficial impact that the use of EPNs could have on the North American corn industry, it is crucial to understand the non-target impact of widely used bionematicides.