Investigating the suppressive potential of generalist predators and entomopathogenic nematodes against Resseliella maxima (Diptera: Cecidomyiidae) in South Dakota

Authors: Pekarcik, Adrian; SNETHEN, OWEN - South Dakota State University; Nielson, Chad; Beckendorf, Eric; Hesler, Louis; Shapiro Ilan, David

Submitted to: Journal of Entomological Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/4/2025
Publication Date: 9/8/2025
Citation: Pekarcik, A.J., Snethen, O., Nielson, C.N., Beckendorf, E.A., Hesler, L.S., Shapiro Ilan, D.I. 2025. Investigating the suppressive potential of generalist predators and entomopathogenic nematodes against Resseliella maxima (Diptera: Cecidomyiidae) in South Dakota. Journal of Entomological Science. 61(2).

Interpretive Summary: The soybean gall midge emerged as a new species and pest of soybean in the northern Great Plains in 2018. Management tools like insecticides are largely ineffective since the damaging larval stages, which occur inside a plant stem, are hidden and protected, so alternative management strategies like biological control need to be investigated. The purpose of this research was to assess the biological control potential of generalist predators that had not been previously exposed to soybean gall midge, and entomopathogenic (insect-killing) nematodes (EPN) which have been shown to kill other gall midge species but have not been evaluated for soybean gall midge. The objectives were to (1) compare soybean gall midge predation rates of six common predator species collected from a soybean field that has never been infested with soybean gall midge, and to (2) evaluate the susceptibility of soybean gall midge larvae to four commercially available EPN isolates in the laboratory, each at three application rates. Generalist predators not previously exposed to soybean gall midge consumed 39 to 98 percent of larvae present in a Petri dish within 24 h, although the addition of soil to the dishes significantly reduced consumption rates for species evaluated in both bioassays. We confirmed that all four EPN species successfully infected and killed larvae, with similar survival rates among EPN species and inoculation rates tested. These results suggest that biological control agents may be a vital component for integrated pest management of soybean gall midge.

Technical Abstract: The soybean gall midge, Resseliella maxima Gagné, emerged as a new species and pest of soybean in the northern Great Plains in 2018. Management tools like insecticides are largely ineffective since the damaging larval stages, which occur inside a plant stem, are hidden and protected, so alternative approaches like biological control need to be investigated. The purpose of this research was to assess the biological control potential of generalist predators that had not been previously exposed to soybean gall midge, and entomopathogenic nematodes (EPN) which have been shown to infect and kill other gall midge species but have not been evaluated for soybean gall midge. The objectives were to (1) compare, in bioassays with and without soil, soybean gall midge predation rates of three ground-dwelling and three foliar predator species collected from a soybean field without soybean gall midge, and to (2) evaluate the susceptibility of soybean gall midge larvae to four commercially available EPN isolates in the laboratory, each at three inoculation rates. Generalist predators not previously exposed to soybean gall midge consumed 39 to 98 percent of larvae within 24 h, although the addition of soil to the bioassay significantly reduced consumption rates for species evaluated in both bioassays. We confirmed that all four EPN species successfully infected and killed larvae, with similar survival rates among EPN species and inoculation rates tested. These results suggest that biological control agents may be a vital component for integrated pest management of soybean gall midge.