Based on information from the website insectforecast.com, it appears the risk of corn earworm flights into Southwestern Ontario has increased significantly over the past week. The University of Illinois Fruit and Vegetable News also reports increased trap counts this week.
Female earworm moths lay their eggs on sweet corn at the green silk stage. One female can lay up to 100 eggs per night over a 10 night period. The eggs incubate for 2- 10 days, depending on the temperature. After the egg hatches there is a narrow window of opportunity to control this pest before it enters the protection of the husk.
During periods of potential corn earworm activity, apply a corn earworm insecticide at 50-60% silk, with a second insecticide application 4 days later. Note: corn earworm populations may have a high degree of resistance to pyrethroid insecticides. The level of resistance varies greatly from year-to-year.
Pheromone trapping is an excellent tool to help monitor localized populations in specific sweet corn fields. For more information on trapping, visit Ontario CropIPM.