Fields across the region are experiencing the year’s first wave of crop pests, according to Dr. Emily Bick, an Extension Specialist of Insects for Field and Forage Crops.
While the black cutworm cutting period is coming to a close with minimal damage reported, other pests are prompting concern.
True Armyworms
A large number of true armyworm adult moths have been spotted flying into fields. While their flight times are currently trailing off, the moths have primarily laid eggs on grassy margins adjacent to fields. Experts are less concerned with the immediate first generation, but are closely watching for a second-generation surge in corn and grasses.
However, first-generation damage is already appearing in specific environments where corn was planted directly into grass cover crops like winter wheat or rye.
Alfalfa Weevil & Slug Pressure
In the southwest part of the state, data from the Department of Agriculture, Trade and Consumer Protection, UW–Madison Extension, and stakeholders revealed that up to 40% of surveyed fields reached the economic threshold for alfalfa weevil. This threshold is met when 40% of the stems display pinhole damage.
Fields suffering high pressure during the first cutting are highly likely to see continued pressure during the second cutting. For heavily populated fields nearing harvest, Bick recommends cutting early to save both time and chemical costs.
Meanwhile, early and heavy rainfall has triggered an enormous amount of slug pressure. While slugs are generalists that attack various crops, they are proving most problematic for soybeans, particularly in conservation cropping systems that feature high amounts of cover crops or crop residue.
Scouting Tips
Because pests do not distribute themselves evenly, accurate scouting is critical for effective management. Bick recommends that farmers scout at least five distinct areas of their fields, utilizing a W-shaped walking pattern where crop size permits.
Growers should also make sure to scout at least 20 meters (about 35 feet) away from the field’s edge, as many insects tend to aggregate along the borders.
“It’s really good to understand what the culprit is,” Bick noted, advising farmers to keep their sweep nets ready to identify pests even if the economic threshold is primarily based on visual defoliation.
For more information and updated pest management tools:
– https://cropsandsoils.extension.wisc.edu/pest-management/insect-pest-alerts/ for signup for the Pest Text Alert service.
– Information on the slugNet: https://cropsandsoils.extension.wisc.edu/slugnet/and the slugNet dashboard: https://connect.doit.wisc.edu/content/e2188e97-840c-49e1-842c-22a638bafe7a/
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