Watch For Black Cutworms This Spring

CHARLESTON, MO.

   The Black Cutworm, goes by several names including floodplain cutworm, greasy cutworm and overflow worm. In SE Missouri we know the cutworm for its damage in corn fields in early spring. However it can also cause damage cotton, soybean, turf grasses, wheat and even vegetables such as tomatoes and lettuce. Each year we see some damage from black cutworm in corn fields with some fields reaching economic threshold. What should you look for and are there management options that will reduce the likelihood of your fields reaching threshold?

    While the black cutworm can over winter in SE Missouri, most over winter on the Gulf Coast or Mexico and migrate north in the spring. Researchers from Missouri and Iowa State released tagged moths in Louisiana and recaptured these same moths 3-4 days later in the Corn Belt. Each moth can lay more than 1000 eggs with the eggs generally laid in low, wet areas of fields with thick vegetation. Damage occurs when larvae feed on seedling plants often times completely cutting off the plant and reducing plant populations below optimum levels. Cool conditions can increase damage potential as it slows plant growth. As the plants move beyond the seedling stage damage is minimized.

   There are several management strategies to help prevent damage to corn or other seedlings. Tillage or an early herbicide burndown at 14 days prior to planting reduces the attractiveness of the field to flying moths. Research has shown that most economic damage occurs from larvae already present in the field at the time of planting. Commercially available seed treatments are the first line of defense. It is critical to scout your field early and often, especially if emergence or overall growth is slowed due to weather, for any potential pest outbreaks. Postemergence rescue treatments are warranted when 1-2 percent or more corn plants are cut below ground or 2-3 percent or more plants have been cut above ground and larvae are present. Larvae are gray to black, 1 to 2 inches long when full grown and form a C when disturbed. In cotton, treatment is needed when stand counts fall below 3 plants/foot of row and larvae are present. In soybeans thresholds are when 20 percent of stand is cut, gaps are greater than 12 inches and larvae are still present.

   For more information on black cutworm, contact your local MU Extension office and ask for guide G7112 “Black Cutworm in Missouri” or find it on the web at http://extension.missouri.edu/. Δ

DR. ANTHONY OHMES: Agronomy Specialist, University of Missouri