A detailed video on how to scout for – and manage alfalfa weevil – is available at the University of Wisconsin Integrated Pest and Crop Management Website.
Harvesting alfalfa is "an excellent form of controlling weevils in first-crop" alfalfa, says Bryan Jensen with the University of Wisconsin Integrated Pest Management Program. "However, you can get pretty good survivorship in cool, wetter weather because they hide under windrows."
Check fields four to five days after harvest if they've seen a good deal of weevil feeding, he says.
The three-minute video shows how to find larvae under leaf litter – and what to do about it. View it here.