Rick Foster, John Obermeyer, Department of Entomology, and Bruce Bordelon, Department of Horticulture and Landscape Architecture, Purdue University
We recently found that a significant number of the ripe fruit had rather large holes chewed in them in one of our strawberry research trials (Figure 1). The first thought was that it was slug damage, but upon further examination, it was discovered that the damage was being caused by variegated cutworms (Figure 2). We usually think of variegated cutworms as a pest of tomatoes and field crops, but they have a rather broad range of crops that they will feed on, including strawberries. While not a common pest of strawberry, they have been documented feeding on the fruit as well as on crowns of young plants, and to cut through the stems of flower clusters. Cutworm damage usually occurs along the edges of fields adjacent to lawns or more favored crops such as lettuce or beans. The cutworms we observed ranged from 3/4 to 2 inches in length, indicating that the eggs were laid over a period of time.
Variegated cutworms are brownish gray to grayish black with distinctive yellow or whitish spots on the back of the first 4-6 abdominal segments. They will reach a maximum length of about 2 inches, then pupate in the soil. Variegated cutworms will overwinter in Indiana as larvae or pupae, but the majority of the population comes from moths that migrate in from southern areas in April and May each year. The cutworms feed at night, during the day they hide under crop residues and matted straw. In the vicinity of damaged berries, gently scrape away the ground cover, there you will find the cutworms, typically curled up on their side (Figure 3.)
Cutworms can be controlled with a variety of insecticides available to homeowners, including Sevin (carbaryl), all the pyrethroid insecticides, and products containing Bacillus thuringiensis, or spinosad. Check the pre-harvest intervals on insecticides before applying. For instance, Sevin (carbaryl) should not be applied within 7 days of harvest, while spinosad can be applied within 1 day of harvest and Bacillus thuringiensis can be applied the day of harvest. Most pyrethroids can be applied within 1 day of harvest.