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Remain on the Watch for Alfalfa Weevil

April 17, 2003

Fluctuations in spring temperatures seem to have slowed alfalfa weevil development. Although confirmed reports of alfalfa weevil larvae have been almost absent, Kevin Black, with Growmark in Bloomington, reported alfalfa weevil larvae were found in Jackson County last week by Alan Mosler, with Southern FS. The warm weather we've experienced over the past week is sure to have accelerated weevil development. Accumulated degree-days (base 48°F), from January 1 through April 13, indicate that alfalfa weevil larval hatch will occur in alfalfa fields in half of Illinois soon (Figure 1). Projected degree-day accumulations (base 48°F) indicate that almost the entire state will have accumulated at least 200 degree-days by April 28 (Figure 2). Larval feeding should be more commonplace as warm weather continues. If you're heading out to check your alfalfa fields, remember, small larvae generally will be found in the terminal tips of the plant. Early feeding is identified as small pinholes in the leaves. As larvae continue to grow, they move down the plant and begin feeding on leaf margins and skeletonizing leaves. If you are out scouting and come across alfalfa weevil larvae and damage, we'd be curious to know what you're finding.--Kelly Cook

Author: Kelly Cook

The Pest Management and Crop Development Bulletin
Executive Editor: Kevin Steffey, Extension Entomologist

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