Alfalfa weevils have been extremely active throughout Kansas this spring, says Jeff Whitworth, a Kansas State University entomologist. Reports of weevil activity started coming in weeks earlier than normal. Unusually mild weather speeded up weevil egg hatching and larval development and wet weather delayed much-needed insecticide applications, he says.
"If you are starting to find pupae and most of the worms are large, robust and maybe even a little sluggish, that probably means feeding activity is about to end naturally. So you will not help the situation with an insecticide application," Whitworth says. If the alfalfa is growing rapidly, harvest a little early instead of treating. "If you do treat, pay close attention to the preharvest interval for the insecticide used."