By Justin McMechan,Thomas Hunt
As of August 7, six new counties have been identified as infested with soybean gall midge in Nebraska. Several new counties have been identified in Iowa, Minnesota and South Dakota and an infestation has been identified in northwest Missouri (Figure 1). In total, 86 counties across five states have been documented with soybean gall midge infestations. If you’re in a county in Nebraska that hasn’t been indicated as infested and you’ve seen injury and soybean gall midge larvae, please contact Justin McMechan justin.mcmechan@unl.edu, Tom Hunt thunt2@unl.edu, or Robert Wright rwright2@unl.edu. Send a photo of the larvae along with a GPS location or land description.
Figure 1. Soybean gall midge infested counties documented in 2018 (red) and 2019 orange across five states (Nebraska, Iowa, Minnesota, South Dakota, and Missouri).
Scouting for Soybean Gall Midge
Be sure to scout all of your soybean fields regardless of whether you see any damage from the road. We’ve observed a number of fields that appear healthy from the field edge but are infested with soybean gall midge. In many cases, the dead or dying soybean plants in these fields have been covered over by healthy plants. Be sure to examine plants that are still green for soybean gall midge larvae. See the Twitter video for how to scout your fields for soybean gall midge.
Adult Emergence and Management
In Nebraska, soybean gall midge emergence in soybean has trickled along at low levels from the past couple weeks until this past Sunday when large populations of soybean gall midge adults were observed at nearly all sites in the east-central part of the state. As of Friday, August 2 a cumulative total of approximately 650 adults had been collected across all sites in east-central Nebraska with no more than 37 adults collected on a single day. On Sunday, a total of 756 adults were collected from eight sites in east-central Nebraska with 261 adults emerging from a single site over a two-day period. No significant numbers of emerging adults have been observed in northeast Nebraska.
With such high numbers of adult emergence in the recent days, many might be wondering if any action is needed. We do not recommend taking any action against soybean gall midge at this point in the season. Emergence of adults has continued since the Sunday collection and we expect emergence to continue through mid- to late-August based on last year’s observations.