Pictured: Alfalfa weevil larvae in net. Photo by K. Hamilton DATCP
Overwintered alfalfa weevil adults are resuming activity, and the 10-day forecast calls for the start of spring egg laying in southern Wisconsin alfalfa fields.
Alfalfa weevil is an early-season pest that feeds on alfalfa leaves and may severely damage first-crop and second-crop alfalfa fields.
Although extreme cold temperatures in January and lack of snow cover may have caused higher-than-normal alfalfa weevil winter mortality and possibly lower larval populations this spring, it is still important to plan for sampling first-crop alfalfa in May.
The Department of Agriculture, Trade and Consumer Protection’s alfalfa surveys are scheduled to begin the week of May 11-17. Crop advisors should likewise start checking fields for weevil larvae at that time.
The larvae are legless, green grubs with a white stripe along the center of their back and a shiny black head capsule. Larvae grow to a length of approximately 3⁄8 inch.
The earliest larvae are likely to emerge by May 7 in Grant and Rock counties.
See a map showing current alfalfa weevil degree day accumulations: https://agweather.cals.wisc.edu/vdifn?type=insect&model=alfalfa-weevil
Learn more about alfalfa weevil: https://cropsandsoils.extension.wisc.edu/articles/managing-alfalfa-weevil-in-wisconsin-alfalfa-fields/
Leave a Reply