Kentucky Expects Few Corn Borers

Spring survey shows Southwestern corn borer numbers should be low this year. Compiled by staff

Published on: May 24, 2004

Corn stubble in several western Kentucky counties was checked this spring for signs of Southwestern corn borer to determine the pest’s potential infestation in this year’s corn crop.

"The good news is looks like it’s low this year," says Ric Bessin, Extension entomologist with the University of Kentucky College of Agriculture.

Southwestern corn borer can overwinter in corn stubble and stubble is checked in early spring for damage and surviving larva. Low numbers in the survey indicate there will be low numbers later in the season when they can cause damage to the 2004 corn crop. This is the sixth year the survey has been conducted and the numbers have been low for the past two years, Bessin says.

Southwestern corn borer has two or more generations per year. The first generation attacks whorl-stage corn and can cause yield losses by stunting or killing plants. The second generation occurs during mid- to late-summer and increases harvest losses through stalk breakage due to the insect tunneling in the stalk.

Southwestern corn borer was the worst corn pest in Kentucky prior to the winter of 1977-78, when a severe winter killed out the population. Between then and 1992, they did not occur in the state but have since migrated back.

"We know winter weather conditions have the ability to kill out the insect," Bessin says. "Because of this, we follow the insect’s survival over winter to give us a heads up to make seed selection and management decisions."

Winter survival is just one of the variables that determine the potential for problems. Planting date is also a key variable. Typically, fields planted after May 10 have an increased potential for this type of damage. If conditions are wet and farmers are still planting after May 25, Bessin says they should consider using a Bt hybrid.