Despite the heat, western bean cutworm activity is increasing. Trap catches over the past week have climbed significantly, indicating that peak flight is here or soon to be here. The counties that have accumulated the most moth catches so far include Chatham-Kent (544), Lambton (256), Middlesex (244), Huron (206), Haldimand-Norfolk (138), Essex (155) and Elgin (105). Click here to see the accumulated map catches for Southwestern Ontario. The Chatham-Kent trap sites with the highest catches are actually still in and around Bothwell which border the three counties of CK, Lambton and Middlesex. Chatham-Kent and Lambton are both currently averaging 9 moths per trap, though some traps have caught 100s in just a few days. To see trap catches for all of our trap sites, click here and view Week 6 maps.
More reps and scouts are finding corn fields with eggmasses at above threshold levels. Though so far above threshold infestations have been mainly found in the greater Bothwell area and south of Tillsonburg, many more fields are going to be ideal now for moths to lay eggs in. Those fields that were not planted with a Bt that protects against WBC need to be scouted. Target fields that are in the early pre-tassel to early tassel emerged stages. In this heat a freshly laid eggmasses can hatch in 4 to 5 days. Remember you want to target a spray application just after egg hatch, if the 5% threshold is reached. Young larvae will hang out in the whorl/tassel of the plant for a few days before heading down to the developing ear.
Don’t spray in the heat of the day during this heat wave. Wait until the evening when temps are in the lower 20s to high teens.