2005 Year in Review

From the Fields – Rust and Rootworms

With the concern over soybean rust and corn rootworms in first year corn following soybean, producers should not forget about black cutworm. With corn being planted in northern Illinois, it is important to review certain aspects about this corn insect pest.

Black cutworms do not over winter in Illinois; rather the moths are blown into the area by wind currents from the south and southwest. Degree-days can be an effective tool to help determine when to start field scouting for black cutworm larvae. The accumulation of degree-days begins with a significant moth flight (nine or more cumulative moths caught in traps over 2 consecutive days).

Black cutworm larvae are expected to begin feeding on and cutting corn with the accumulation of approximately 300 degree-days, base 50 degrees F, after an intense capture occurs. Cutting dates for your area can be predicted by using the Degree-Day Calculator at the University of Illinois IPM and WARM

Fields or areas of fields in which early-season weeds were growing at the time moths flew into the area are at a higher risk than weed-free fields. If tillage or herbicides eliminate weeds 1 to 2 weeks before planting, black cutworms that had been present probably starve to death. The presence of weeds only a few days before planting increases the likelihood of cutworm damage if larvae are present in the field.

Cut, missing, or wilted corn plants are typical symptoms of black cutworm larvae damage. Early signs of cutworm feeding are pinholes in the leaves of newly emerged seedlings. Feeding mainly at night, larvae will move up the row as they feed. On average, one larva may cut three or four plants in its lifetime.

A rule of thumb treatment guideline has been 3 to 5 percent cutting. One should also consider the location of the cutting (above or below the growing point), size of the cutworm, and the soil conditions (moist or dry). Various rescue treatments for black cutworms are shown in the 2005 Illinois Agricultural Pest Management Handbook.

For further information on this pest, including scouting and management strategies, see the University of Illinois black cutworm fact sheet at this website: Click Here or contact your local Extension office.

by  Editor, theCity1.com
May 4, 2005