Agronomy Talk

Agronomy Update

European Corn Borer Feeding Begins

Published on Wednesday, July 1, 2015

The long awaited European Corn Borers have started hatching and feeding on corn plants. See Christy's scouting notes below for more information on what we are seeing with the Corn Borers throughout central Indiana and what to expect in the coming weeks.

Borer Feeding in Whorls and Continued Watch for Moths and Eggs
Christy Kettler | Sales Intern | Central Indiana
June 22 – June 26, 2015

Across corn fields in central Indiana, I have discovered a borer in a whorl in as much as 9% of plants. This is the first generation of borers to invade the area. Second and third generations should be expected to start growing this season as well.

The feeding that began this week appears as tiny burrow holes in a straight line across the unrolled leaves. The manure from the insects is often a good indicator of their presence as well. By pulling the whorl out of the plant and unrolling the immature leaves, the borer can be found inside. They are about 1/8th of an inch long and are a pale whitish yellow color with black heads. While these insects are in their infant stages, they will continue to eat and grow rapidly before reproducing. The damage can be found by walking fields and looking first in the more heavily populated areas with lush growth. An expected yield loss of 7 bushels per borer is a rough rule of thumb when deciding what course of action to take if the field is infested.

Corn Borer Damage on Corn 

Egg masses can also be detected in fields at this time, which means they will soon hatch and begin eating. Keep watch for flies and ladybugs that are predators to harmful insects such as these borers.

Ideally, we would recommend spraying an insecticide between the time the egg masses hatch and when they begin to burrow their way down deep into the whorls. However, we also want to preserve the population of good bugs so that they will be helpful for coming generations. If all of the borers predators are killed off before the second and third generations arrive, spraying will have to be increased. Balancing the timing and population control is crucial for the best yield come harvest time. 

The traps throughout north central Indiana have shown some European Corn Borer moth flight action. Be sure to check the Purdue University Entomology and Agronomy updates for more information.  

Look for my findings again next week!


If you have any questions about these findings or would like more information, please reach out to myself or your seed advisor. 


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Denny Cobb

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