Slug infestations can pose a major threat to emerging soybean crops, often leading to damaged stands or costly replanting. In the Mid-Atlantic region, where many farmers practice no-till agriculture, traditional slug management strategies can be ineffective. Tillage is considered the most reliable control method, but alternatives are needed for fields where tilling is not feasible.
University of Delaware entomologist Mike Crossley is leading a research effort, supported by multi-year Soy Checkoff funding from the Delaware Soybean Board, Maryland Soybean Board, and Maryland Grain Producers Utilization Board, to identify natural slug control options. “Slug baits are commonly used, but their effectiveness is highly variable,” Crossley explains. “Rain can wash them away, hot dry weather can reduce consumption, and environmental concerns remain. We need alternative solutions that work under real-world conditions.”
Crossley and his team are investigating parasitic nematodes—microscopic worms that naturally attack slugs. While some nematodes infect soybeans, thousands of other species parasitize a wide range of organisms, including slugs. Using field-collected slugs from Delaware and Maryland, lab studies focus on slugs that show signs of nematode infection. DNA testing identifies the nematode species and evaluates their potential as biological control agents.
With additional funding from the United Soybean Board, the research has expanded to include slugs from Kentucky, Ohio, Pennsylvania, Tennessee, and Virginia. The team has successfully identified multiple nematode species, including two that appear to parasitize living slugs. “Even if infections aren’t immediately lethal, nematodes that disrupt slug feeding can protect young soybean plants,” Crossley notes.
Some nematodes discovered are phoretic, hitchhiking on slugs to new locations, while others are necromenic, feeding on slugs after death. The goal is to identify true parasitic species that actively damage living slugs, offering a potential natural control method.
In addition to developing nematode-based products, the research explores ways to enhance natural nematode populations in the field. When nematodes are present, they can infect a substantial portion of the slug population—up to 60% in some cases—helping to naturally suppress slug pressure without chemical baits or tillage.
Crossley emphasizes that slug pressure varies annually and regionally, and supporting natural nematode populations could provide a sustainable, low-impact solution for soybean growers. As the project continues, findings from this research may pave the way for practical, environmentally friendly tools to protect soybean yields from these persistent pests.
