Pest Alert: Black Cutworms

LAWRENCE, Kan. (DTN) -- Entomologists in Indiana, Missouri and Ohio are urging growers to be on alert for high black cutworm populations this spring.

"With the recent weather fronts moving through the upper Midwest, (black cutworm) trap catches increased dramatically in several areas over the past week," Purdue Integrated Pest Management Specialist John Obermeyer wrote in a university newsletter. "These types of catches signal that we may see some feeding activity this growing season."

Entomologists from the University of Missouri and Ohio State University also noted higher-than-normal moth populations this spring. The moths can lay eggs in any number of fields, but corn fields are most at risk right now, as the hungry first generation of cutworm larvae could coincide with young corn plants emerging across the Midwest.

Knowing which fields to scout can be tricky. Not only are the cutworms black or gray in color, but they also curl up at the base of plants under soil and residue during the day, and only emerge to feed at night.

A University of Missouri guide notes that fields at the most risk of damage are low-lying, wet, located near vegetation such as woods or a weedy meadow, have heavy residue or winter annual weeds, were planted late to corn, or have a history of black cutworm problems.

The guide recommends scouting 25 consecutive plants within a row in 10 areas in a field for evidence of cutworms feeding on leaves and cutting the plant above or below ground. A field's injury level can be calculated by dividing the number of damaged plants by the total 250 plants scouted.

Treatment thresholds vary by region. Missouri thresholds are 3% to 4% for underground cutting and 6% to 8% for aboveground damage, and an Ohio State University guide recommends that if 3% of plants are injured, corn is between the second- and six-leaf stage, and larvae are less than an inch big, treatment is warranted.

Foliar insecticides can be fairly successful at treating cutworm infestations, Ohio State University entomologist Andy Michel noted in a university newsletter. For details on the best insecticides for cutworms, see this Ohio State guide: http://goo.gl/…

Keep scouting corn until plants are in the five- to six-leaf stage, and then continue to scout other crops like soybeans and wheat for two weeks after emergence. Black cutworms prefers wet soils, so growers with cool, wet planting conditions might find that their corn is growing more slowly and will be susceptible longer. In drier soils, cutworms will actually uproot a growing plant and drag it into its burrow to eat, so keep an eye out for missing plants.

For more details on scouting and treating cutworms see this University of Missouri guide: http://extension.missouri.edu/…, this Ohio State guide: http://goo.gl/…, or this Purdue alert: http://goo.gl/….

Emily Unglesbee can be reached at emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(AG)

Copyright 2014 DTN/The Progressive Farmer. All rights reserved.