In the haste to plant corn, producers with stands of alfalfa should not
neglect scouting efforts for alfalfa weevils.

Mike Gray, U of I Extension entomologist, said southern Illinois producers should begin scouting now as leaf feeding by first and second-instar larvae is under way in many fields across southern Illinois. Central Illinois producers should begin scouting within the next week to 10 days.

"Scouting is important to determine whether or not economic infestations are present and to determine if rescue treatments or an early harvest are warranted," Gray said.

Alfalfa should be sampled by making a U-shaped pattern within a field, taking care to avoid field edges, Gray said. Randomly collect 30 stems and place them in a bucket. Following the collection of all stems, dislodge the larvae from the stems within the bucket and determine the number of weevil larvae per stem.

"If 25 percent to 50 percent of leaf tips have been skeletonized and you find three or more larvae per stem, a management decision is required," he said.

Early harvest of the first hay crop is a sound management option. If this cultural management approach is selected, monitor the regrowth carefully for any signs of feeding activity.

An insecticide rescue treatment may be required following an early harvest if both larvae and adults are causing injury to more than 50 percent of the crowns and regrowth is not occurring for 3 to 6 days.

For a more complete description of scouting procedures and life cycle information on this insect pest, click here, or read The Bulletin online

SOURCE: University of Illinois.