Know which insect you are dealing with before making decisions

Know which insect you are dealing with before making decisions

Corn Illustrated: Sometimes damage can look similar to damage by another insect.

If you've farmed for a while, you've heard of "shot-hole damage." It's what happens to corn leaves when the first generation of European corn borers hatch and chew through leaves. It's already past time for that – they're likely working on the second brood now. But the tell-tale shot holes still remain.

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They are called shot-holes because they look like round "shots" through the leaf. They look that way because corn borer larvae typically chew through leaves still in the whorl. When the leaves unroll as the plant grows, the holes of the insect chewing through one side and out the other are visible, lined up like shot holes.

Corn borer? Not this time. These holes were caused by stink bugs. At first glance they resemble corn borer damage. However, only the holes are ragged.

If you are growing GMO corn with corn borer tolerance, you may have not seen much of this type of damage for a while. If you grow non-GMO corn, European corn borer has been making some noise lately, even in the Eastern Corn Belt where it's usually not as prevalent. It's not always enough to justify spraying, but it's noticeable and occasionally rises to that level.

Here is the interesting part. European corn borer isn't the only insect that puts holes in a row across corn leaves. An Indiana scout, Christy Kettler found and photographed a leaf with four holes across it. But it turns out these holes were due to stink bug feeding. If you look closely you will see that the holes are ragged and not circular, precision shot-like holes.

But at first glance or if you haven't seen corn borer feeding from the first brood for a while, you might jump to the wrong conclusion.

Kettler, a Purdue University junior, is an intern scouting for Beck's Hybrids in north-central Indiana this summer. Stink bugs is one of the insects that she has encountered in the field. If left unchecked, and with enough damage, secondary infections can come in and cause more harm, entering where the stink bugs chewed through leaves.

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She advises scouting and knowing what's in your field. And when you find damage, be sure to identify the cause. Even if you can't do anything about it this year, it might help you make better management decisions for next year.

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