If you didn’t plant genetically-modified-corn hybrids that protect against European corn borers then it’s time to start scouting for these yield-robbing pests.

"Proper scouting is essential to managing European corn borer infestations," says Steve Hyronimus, district agronomist, Mycogen Seeds. "The flights of the moths vary each year due to differing crop stages and weather conditions. Typically, flights begin the middle weeks of June and last for two to three weeks. This year's early planting will push the schedule ahead for scouting."

Begin scouting when the top corn leaf can be stretched to 18 inches tall. Moths tend to seek out the tallest plants first.

During the daytime, moths hide in tall grass and shelterbelts. In the warm evening hours, they deposit their eggs on the underside of corn leaves. Eggs hatch in four to nine days, depending upon the temperature. Larvae feed first in the whorls of the corn plant; so look for shot-holing in the youngest leaves.

Randomly pull out the whorls from 10 plants in five locations in the field. Count the 1/8 inch to 1/4 inch long black-headed larvae in the whorl. Input this number into one of the various formulas to estimate threshold for treatment.

"Treatment of the 1/8 inch to 1/4 inch larvae is the most desirable stage," Hyronimus concludes. "Larvae at 3/8 inch are soon going to tunnel into the whorl and control measures will then be ineffective. Scout weekly until egg masses are located and then scout every three to five days.

For more information, contact your local agronomist or crop consultant. If you would like to speak with an expert from Mycogen Seeds send an e-mail to Stephen Smith, agronomy services manager with Mycogen Seeds at sesmith@dow.com.

Mycogen Seeds Agronomy Update