Peak Alfalfa Weevil Feeding Expected

Pictured: alfalfa weevil feeding damage. Photo by K. Hamilton/DATCP

Damage by alfalfa weevil larvae has increased in the past few weeks and will become even more pronounced in the weeks ahead, especially if rain delays the harvest of first-crop alfalfa.

This is the latest news from the state Department of Agriculture, Trade and Consumer Protection. Department specialists expect peak alfalfa weevil feeding through mid-June.

Estimates of leaf tip feeding recorded during this week’s alfalfa surveys mostly varied from 10-20 percent, though a few scattered fields had higher larval pressure (3.9-8.6 per sweep) and showed above-threshold levels of tip defoliation ranging from 40-70 percent.

The peak alfalfa weevil damage period happens in Wisconsin between 600 and 800 degree days and is now starting in Grant, Iowa, and Rock counties.

With the first alfalfa harvest less than 10 percent complete and several days of rain in the forecast for late May, routine scouting is strongly recommended for unharvested first-crop alfalfa fields until new growth of the second crop is established.

Alfalfa stands with 40 percent or more of the leaf tips throughout the field showing weevil feeding would benefit from an early cutting (for fields more than seven days from the scheduled harvest date).

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