Corn earworm pressure often increases as we head into September. With turbulent weather patterns originating in the Gulf of Mexico, flights of airborne moths are generally quite high. As the tradewinds mix with the cooler air of the great lakes, these high populations are dropped into Southern Ontario. Any sweet corn at the green silk stage is highly susceptible to corn earworm infestation.
For earworm control, cover green silks with an insecticide such as Coragen or Voliam Express. Avoid insecticides from the pyrethroid family. Corn earworm are known to be resistant to the pyrethroids. Lannate TNG is a good rotational partner for Coragen and Voliam Express.
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.
Two different types of pheromone traps used for corn earworm. The heliothis trap (rear) and the hartstack trap (front).
Information for commercial vegetable production in Ontario
