By Scout Nelson
The 2025 alfalfa weevil season has been slower than past years, though some fields across Minnesota have reported high populations, especially in mid-June. Most larvae are now in their mature stages and will stop feeding soon, but younger larvae are still present in some samples.
Bright green third and fourth instar larvae are dominant, but pale-yellow younger larvae suggest weevil activity may continue. Scouting is important to identify if individual fields reach economic thresholds. So far, many areas have not shown weevil numbers high enough to justify insecticide use.
According to degree-day models, alfalfa weevils should have completed their feeding cycle around June 16. However, spotting younger larvae may indicate variation in development timing or influence from different weevil strains. The western strain, which develops later than the eastern strain, could be extending the season in some regions of Minnesota.
Warm winters could also lead to staggered generations, though this is less likely in 2025 due to cold soil temperatures. If younger larvae are still seen in your fields, continue scouting until the end of June.
Treatment guidelines remain like previous years. For scouting and insecticide recommendations, refer to last year’s article titled “Alfalfa weevil season begins in 2024.”
“Remember there are not very many pesticide options for use in alfalfa.” Products like chlorpyrifos can be used until June 30, 2025, only if they were registered this year. Products such as Lorsban cannot be used on crops this season.
For updated pesticide details, check the Minnesota Department of Agriculture's website. Proper scouting and awareness of regulations can help protect alfalfa crops and reduce unnecessary chemical use.
Photo Credit:gettyimages-0shut0
Categories: Minnesota, Crops, Alfalfa