Efficacy evaluation of biological control agents against wireworms in organic production

Wireworms, the larval stage of click beetles (Coleoptera: Elateridae), are generalist subterranean herbivores that cause significant damage in a variety of crops. Managing wireworms has been a challenge due to their long-life cycle, subterranean living habitat, and ability to survive wide range of host plants. Although there are a few insecticides available for conventional farming, there is no effective alternative control measure against wireworms in organic production. Thus, there is a critical need for developing effective non-chemical control protocols against wirewormsRecent studies suggested that entomopathogenic nematodes (EPN) and fungi (EPF) may offer protection against wireworms, but their efficacies are influenced by soil type and wireworm species. Focusing on one of the most damaging species in the PNW, the sugar beet wireworm Limonius californicus, we propose to conduct a series of experiments to evaluate and compare efficacies of EPF, field-collected and commercial EPNs, and combined EPF/EPN treatments against wireworms in organic vegetable production. We will extract (and rear) naturally occurring EPN from the organic farm soil, and then apply field and the commercially available Steinernema feltiae nematodesthe EPF Metarhizium brunneum, and the EPN/EPF combinations in wireworm infested field plots, as well as experimental greenhouse pots. With the knowledge of soil type, we are expecting to not only determine the most effective entomopathogenic treatment against the sugar beet wireworm, but also allow successful establishment of the biocontrol agent in the organic farm soil.