Alfalfa growers should watch their fields for signs of army cutworm feeding, says Bruce Anderson, a University of Nebraska forage agronomist.
“If your alfalfa seems slow to get started this spring, examine fields closely for cutworms,” Anderson advises.
The worms caught many growers by surprise the last few springs, and conditions are favorable to worms again this spring, he adds.
They feed at night on emerging leaves near plant crowns. During the day they can be found in loose soil surrounding plants. Scratch around in the soil to find the cutworms if you don’t see them right away, says Anderson.
Count the number of cutworm larvae per square foot in several locations throughout the field to find out if it would be economical to spray. The economic threshold is four or more army cutworms per square foot on established alfalfa, but just two per square foot in fields seeded last year.
Once the crop gets 4-6” tall, spraying probably won’t be beneficial unless there is a lot of active leaf feeding.
Synthetic pyrethroids are the best insecticides for controlling army cutworms in alfalfa.
“Before spraying, read and follow label directions to safely apply the correct rate,” says Anderson.