Biological control of the soybean aphid by Aphelinus certus

George Heimpel, Entomology

Background

The soybean aphid, originally native to Asia, is the most serious insect pest of soybeans in Minnesota. Modern control centers around the use of broad-spectrum insecticides, which are expensive and inherently risky to native pollinators and other beneficial insects. Many growers are eager for more environmentally sustainable and cost-effective solutions.

The parasitic wasp Aphelinus certus is one important natural enemy of the soybean aphid. Like the aphid, it was inadvertently introduced to the U.S. from Asia in the past decade. A. certus now presents an appealing, potential alternative to exclusive chemical control, and a natural addition to the toolbox of integrated pest management (IPM) practices.

Right now, there is a gap in knowledge about how aphids and A. certus interact on Minnesota soybean fields. We do not yet know what environmental factors may affect wasps’ ability to suppress aphid populations, or how many wasps are needed to keep aphids below economically damaging levels. We also don’t know where A. certus overwinters.

This project will run field, lab and mathematical simulations to improve our practical understanding of A. certus biocontrol. Researchers will determine the level of parasitism necessary for successful biocontrol, as well as the extent to which A. certus’ presence can reduce pesticide use. The team will also explore how A. certus biocontrol programs could protect two endangered prairie butterflies in western Minnesota – the Powesheik skipperling and the Dakota skipper.

Research questions

How effective is A. certus in suppressing soybean aphid populations in fields across Minnesota?
Where is A. certus currently in Minnesota and how abundant is it?
Where does A. certus overwinter in Minnesota – in soybean fields, on buckthorn, in soybean aphids (which overwinter on buckthorn) and/or in a different aphid host?
What population of A. certus is necessary to suppress soybean aphid populations below the economic spray threshold?

Practical implications

This work will help soybean growers make informed decisions in their soybean aphid IPM programs. Specifically, knowledge about the levels of parasitic wasps in the field may help reduce insecticide applications for a lower cost and healthier native pollinator community.

Results will be shared directly with the Minnesota soybean growing community via a partnership with the Minnesota Soybean Research & Promotion Council.