Researchers Find New Soybean Gall Midge Parasite

By Scout Nelson

Researchers have confirmed the discovery of a second species of parasitic wasp that attacks the soybean gall midge (SGM), a major soybean pest. This newly documented species, Synopeas ruficoxum, joins Synopeas maximum as a natural enemy capable of helping control SGM populations in the Midwest.

“Our exploration into the natural enemies of soybean gall midge (SGM) led to the discovery of a second species of parasitic wasp attacking (parasitizing) this pest in soybean fields,” researchers explained.

“We recently published a scientific paper documenting this wasp, called Synopeas ruficoxum, from SGM infestations in several locations in Nebraska and confirming that it indeed parasitizes SGM.”

Like the first identified wasp, S. ruficoxum parasitizes immature soybean gall midge by laying its eggs inside the pest’s eggs or larvae. The developing wasp then consumes the SGM larvae from within, providing natural biological control. The species name “ruficoxum” refers to the reddish-brown color of part of the wasp’s leg.

Before this discovery, S. ruficoxum had only been recorded three times in Canada, with no confirmed host insect. This raises questions about the true range of the soybean gall midge and whether the wasp also targets other insects.

The research team continues to study how parasitism rates by both S. ruficoxum and S. maximum vary across the Midwest. To date, both species have been found in soybean fields in Minnesota, Nebraska, Iowa, and South Dakota.

“Our goal is to deepen our understanding of the parasitoids targeting SGM, with the aim of conserving these beneficial insects to enhance natural pest control of this pest,” the team noted.

This study involved collaboration with scientists from the Naturalis Biodiversity Center, the Florida Department of Agriculture and Consumer Services, and the Eastern Nebraska Research, Extension, and Education Center. Funding support came from Sustainable Agriculture Research and Education (SARE).

The discovery highlights the importance of beneficial insects in managing crop pests and provides soybean producers with hope for improved natural control methods in the future.

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