Peak Corn-Cutting Window Opening
Photo Credit: Roger Schmidt (top) & Bryan Jensen (bottom), University of Wisconsin-Madison
Black cutworm peak corn-cutting window is expected to open in the Southern region next week (~May 19th), in the Central region (~May 25th) & in the Northern region (~May 30th) — so it is time to go scout your corn fields!
Critical Economic Information
The economic threshold for black cutworms is roughly around 3-5% damaged plants. However, larvae are most susceptible when they are < ¾ inches long — so use the 3% damaged plant threshold here. If they are >¾ inches long, it is best to use the 5% damaged plant threshold. This also means the younger the larvae are when you find them, the best chance you have to avoid economic damage. Critically, if most of your larvae are >1 ¼, it is not worth spraying, as they are about to pupate so this will not help.
Scouting
Find larvae by slowly excavating around the base of cut corn plants. Be aware – small larvae do blend in with soil. Refresh your Black Cutworm Scouting Skills.
Broadcast foliar insecticide when the suggested threshold is reached. Rescue treatments can be very effective
for black cutworms if infestations are found soon enough. However, hot, dry weather can reduce the
effectiveness of these treatments by causing the black cutworm to spend more time underground, thereby reducing exposure to the insecticide. For insecticide options, see UW-Madison Extension Book A3646.
Learn more with DATCP’s Black Cutworm Trapping Network, FieldNotes.
If you found this information on the web, you can sign up for insect pest text alerts here.
