Significant Flights of Black Cutworm Moths Arriving in Some Parts of PA

Again this year Penn State Extension and the Department of Entomology are monitoring black cutworm populations with pheromone traps. As moths arrive, if we capture eight or more moths over the course of two nights (a "significant flight"), there is an elevated risk in that particular area of cutting damage by black cutworm caterpillars later in the spring. We have now detected significant flights of black cutworm moths at four locations in PA: near Fredericksburg and Bellegrove Lebanon County, near Manheim in Lancaster County, and near New Paris in Bedford County. We continue to trap for moths, but will begin degree-day accumulations to predict the timing of cutting for Lebanon, Lancaster, and Bedford Counties to inform folks when they should be scouting fields for damage.

Cutting damage tends to occur 300 degree-days following significant flights, so the time to scout has not yet arrived. These significant flights should not prompt you to add insecticides to any herbicide applications you will be doing soon, because applications of insecticides without knowing your local cutworm populations are unlikely to be effective or profitable. If you deploy insecticides this way and do not see damage, an equally plausible explanation is that caterpillar populations in your area were low.

When you scout your fields, note that black cutworm caterpillars can damage corn from first emergence up through V4 (damage to V5 is rare). Economic thresholds for black cutworm damage to corn are 2, 3, 5, and 7 caterpillar-cut plants per 100 seedling-, V2-, V3-, and V4-stage plants. For young plants, cutworm damage can look like a series of symmetrical holes through the leaves (see photo). Remember that if cutting damage is found, rescue treatments are usually the most efficient and economical tactic for managing black cutworm. For more information, see the Penn State Extension fact sheet on black cutworm.