Black Cutworm Moth Catch Moderate, but Increasing By Wayne Bailey

Black cutworm pheromone traps began capturing moths during the last week of March in central Missouri. Numbers of moths captured have increased steadily during the past few nights, but number of moths captured have not reached or exceeded the number designated as an intensive capture of moths (8 moths captured over two nights in a sticky wing trap, or 17 moths captured over one night in a Texas cone trap) Numbers or moths by county can be found on the web at (http://ipm.missouri.edu/SEMOmothtrap3.htm).

As of April 11, moth numbers captured per night have approached , but not reached or exceeded the number needed to be declared an intensive capture. Once an intensive capture is achieved at a location, the date of capture is used as a "biofix" in the Missouri black cutworm predictive model. Slightly more than 300 degree days are required to accumulate from the time of a "biofix" event until larvae begin cutting corn plants. NOTE: warmer than normal temperatures can speed the development of larvae, whereas cooler than normal temperatures can slow black cutworm larval development.

Damage: Third instar and smaller larvae cause small "window pane" feeding on plant leaves where they remove the chlorophyll (green) layer of tissue, but are unable to bite completely through the leaf surface. They also may notch the edge of leaves. Once larvae grow to the 4th instar stage of development they are able to cut plants at the ground surface or below ground. This type of feeding can seriously reduce plants stands to unacceptable levels. Producers are encouraged to begin scouting corn fields a few days prior to the date of predicted cutting by larvae to determine whether foliar feeding by small larvae is present. Scouting should continue every few days until plants reach the 5-leaf stage of growth. The economic threshold is based on the percent of plants cut above or below ground. Below ground cutting is more damaging as the growing point of the corn plant can be destroyed. Additional information is available in MU Guide G7112, "Black Cutworm in Missouri".

Management: Several insecticides are labeled for effective management of black cutworm as "rescue" treatments. Cruiser and Poncho seed treatments give some control of black cutworm larvae with variable results found in Missouri field trials. Herculex transgenic Bt corn seed designed for control of European corn borer has produced good to excellent control of black cutworm larvae in field trials.

* Designates a restricted use insecticide. Read and follow all label instructions

Wayne Bailey Entomology 573-882-2838 or 573-864-9905