We have begun our state-wide trapping and monitoring program for corn earworm (Figure 1). The latest trap catch information can be found here. Traps have been placed at seven Purdue Agricultural Centers throughout the state. Trapping will begin June 17, 2021. Please refer to E-31 to learn more about corn earworm identification and management.
Figure 1. Corn earworm adult on silk. (Photo by John Obermeyer.)
Management and insecticide sprays target the eggs that are laid on fresh corn silk. If no field corn in the area is silking, which is true for most this year, use a threshold of 1-3 moths per night per pheromone trap. You only need to spray your sweet corn if it has silk present. We recommend the first application around 50% of plants at silk stage. When field corn begins to silk and green silk is present the threshold increases to 10 moths per night in the trap. Eggs are laid individually on developing silk. They hatch within 2-5 days and the larvae follow the silk channel down into the developing ear to feed. Once inside the ear, there is no effective control. Therefore, monitoring and spray coverage are key. You want the hatching larvae to experience a lethal dose. See ID-56 for a complete list of spray recommendations, but briefly for organic production Bt products (Entrust®) are available and provides good control. For conventional commercial growers, we recommend Coragen® followed by Radiant®.
While there is no established threshold for trap catches and damage to hemp, we are also monitoring in this crop as CEW damage the buds. If you would like a trap in your area, especially if you are a hemp producer, please contact me at lingwell@purdue.edu.