Research conducted
We recently wrapped up studies aimed at finding better management strategies for two major soybean pests: the soybean gall midge and soybean aphid. To combat the soybean gall midge, we evaluated 12 different soybean varieties in our laboratory to identify natural resistance (i.e., host-plant resistance).
Findings
In “no-choice” tests where we forced the insects onto a single variety. These soybean lines represent a diversity of soybean genetics that were identified as being potentially resistant or susceptible to gall midge in a larger project funded by the North Central Soybean Research Program (NCSRP). Soybean line PI 567440 showed strong potential, ending up with significantly fewer larvae than the susceptible checks. Meanwhile, line PI 3399119 managed to stunt larval maturity and line FC031630 reduced the number of emerging adults. In “choice” tests where we gave the midges the freedom to pick where to lay their eggs, they actively avoided several varieties, laying significantly fewer eggs on PI 567440, PI 438112B, PI 384474, PI 081763, PI 437116 and PI 398975 compared to one or two of the susceptible checks.
Our team also explored new scouting and cultural control methods for soybean gall midge. We tested an “Eavesdropper” audio tool designed to listen to plant vibrations for early pest detection. While we found it was unable to distinguish between healthy plants and those infested with gall midge, it successfully identified soybean aphid infestations, showing future promise as an aphid scouting tool. Additionally, when we studied the pest’s lifecycle, we found that the depth at which gall midge larvae are buried in the soil drastically impacts their survival, highlighting tillage as a potential tool to disrupt their development.
Finally, we ran an insecticide efficacy trial to monitor how various commercial insecticides handled an initial pressure of 60 aphids per plant, which delivered a critical warning regarding Warrior II. This pyrethroid chemical completely backfired on us; by weeks two and three, the plots we treated with Warrior II actually had significantly more aphids than our untreated control plots. This provides further evidence of continued pyrethroid resistance in our aphid populations and suggests the insecticide likely flared the pest population by wiping out beneficial, predatory insects instead of the aphids. In contrast, all the other commercial insecticides we tested worked well, successfully keeping aphid numbers low across the entire 21-day trial.
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Graph shows aphid control using various insecticides and the effect on the number of aphids per plant.
