Pest and Disease Pressure Rises in Midwest

Monday, June 12, 2023

After a relatively quiet start to the 2023 growing season, the first full week of June brought about a flurry of pest infestations and diseases.

Here's a rundown on pest alerts DTN has received this week from extension entomologists, pathologists and crop scouts around the Midwest:

SOYBEAN GALL MIDGE

As DTN reported earlier this week, the first male soybean gall midge of the season was detected in Nebraska on May 26, followed by the first female on May 31 near Mead in east-central Nebraska. By June 4, adults appeared in traps near Wahoo, Havelock and Weeping Water, as well as in northeast Nebraska near Randolph. Read more about this year's initial emergence here: https://www.dtnpf.com/….

On June 6, Iowa reported two male adult soybean gall midges in emergence cages near Sutherland. Since the Soybean Gall Midge Alert Network began monitoring efforts in the state, this is about one week earlier than previous captures. The pest also was discovered in more traps in Nebraska, including near Davey, Memphis, Walton and Syracuse.

White larvae were found on soybean plants near Mead, the epicenter of emergence this year, on June 7. Orange larvae were reported on yellow sweet clover in the area the following day.

SOYBEAN APHIDS

In southern Minnesota, Extension Entomologist Bob Koch reports that soybean aphids have begun colonizing soybean fields. The pest was found in fields near St. Paul and Lamberton during the past week. While infestations are still below thresholds for treatments, Koch reminded growers to scout their fields as the month progresses.

Several factors -- such as weather conditions, the quality of the soybean plants and the presence of natural predators -- will determine the ultimate size of any aphid infestation, Koch wrote. He continued that aphids often appear first in early-planted, smaller fields with wooded borders containing buckthorn.

Scouting should begin in mid to late June and continue every seven to 10 days thereafter. Use the threshold of 250 aphids per plant, with most plants infested, as the trigger to apply an insecticide treatment. He added that many soybean aphid populations are resistant to pyrethroid insecticides, and that many treatments will also kill beneficial insects such as parasitic wasps. Read more here: https://blog-crop-news.extension.umn.edu/…