Alfalfa Weevil Update - 05/02/25 (FINAL)

Just like that…alfalfa weevil scouting season is complete. Harvest began in parts of the District this past week and many larvae are forming pupal cases that will transition to adults. Here are the season’s final counts:

Note the 4 sites on the LH side of the graph. All were sprayed and while larvae numbers have rebounded, they illustrate the effectiveness of control in most situations.

With harvest imminent – what next? Adults will chew their way out of webbed pupal cases in four to seven days and may feed on plants (including stems) until temperatures warm and they look for cooler areas (under leaf litter in alfalfa fields or in nearby shaded areas) for oversummering. Adults will return to fields (or resume activity in the same field) when cooler temperatures return in fall, doing a little feeding then depositing eggs in stems when daytime temperatures > 48 degrees. They can overwinter as eggs or adults.

I would like to take this opportunity to say thank you to the cooperators who allowed me to scout fields this season. It was very appreciated! If you are interested in a deeper dive into some of these numbers and what they may mean, drop me a line at dhallaue@ksu.edu .