Hay growers in the southern half of Illinois should be scouting for alfalfa weevil damage, say University of Illinois entomologists. Producers started reporting significant alfalfa weevil activity March 25-28. Alfalfa fields as far north as northwestern Bond County were said to be showing noticeable injury between March 30 and April 3. Some fields farther south have been damaged significantly. "Alfalfa weevils are tearing apart alfalfa fields in the south," states Kevin Black, insecticide-fungicide technical specialist with Growmark. Many producers getting ready to plant corn have been surprised by the severity of the injury this early in the season. The relatively early warm-up in late March activated weevils in a large area of Illinois, say the entomologists.
In southern and central Illinois, weevil larvae begin to hatch from fall-deposited eggs at around 200 degree-days and from spring-deposited eggs after 300 degree-days. Start scouting when 250-300 degree-days accumulate, experts suggest. An early peak of third-stage larvae from overwintering eggs occurs after 325 degree-days; a second major peak of third-stage larvae from spring-deposited eggs occurs after 575 degree-days. Learn more about alfalfa weevil activity in Illinois at www.ipm.uiuc.edu/bulletin/article.php?id=663.