Alfalfa weevils are hatching

Iowa has steadily accumulated growing degree days (DD) all through March. One of the first insects to hatch is alfalfa weevil. In general, we can expect egg hatch around 200 DD south of I-80 and around 250 DD north of I-80. Most of the state has already hit those benchmarks.

 

Accumulated growing degree days (base 48F) in Iowa form 1 January - 2 April 2012. This map is updated daily (click here). Map courtesy of Iowa Environmental Mesonet, ISU Department of Agronomy. 

 Alfalfa weevil is an important defoliator because adult and larval feeding can reduce tonnage and forage quality. If plants are greater than six inches, use a sweep net to initially sample. Insecticidal treatments are based on crop value and plant height. Read this recent ICM News Article for management guidelines.

Alfalfa weevil adults are brown and hairy, have elongated snouts and elbowed antennae. Photo by Joseph Berger, ipmimages.org.