Bryan Jensen, University of Wisconsin Integrated Pest Management Program, takes you into the field to show you how to scout and manage alfalfa weevil in Wisconsin field crops. Scouting AFTER first cut harvest is different than scouting before harvest because it includes checking during regrowth for green up. Also, the economic threshold moves up to 50% on the count of plants showing damage.
If environmental conditions are favorable, larvae may survive cutting and harvest, and feed on newly forming crown buds, which significantly delays regrowth and lowers yields. Revisit fields with elevated first crop defoliation within four to five days of cutting. Check to make sure crown buds are forming.
Look for larvae on the soil surface, under leaf litter and at the juncture between soil and the alfalfa crown. During cool, cloudy weather you may find weevils feeding on new alfalfa buds during daylight hours.
For more information:
or your local UWEX agent.