Danny Greene scouts fields as part of his Greene Crops Consulting business, based in Franklin, Ind. One of the pests he has found recently is the European corn borer larvae. This generation feeds in stalks.
A tell-tale sign that corn borers are present is shot-hole damage on leaves that have emerged from the whorl recently. Greene says this happens since larvae are in the whorl, and fed through a leaf. When the leaf unfurls from the whorl, there is a pattern of holes across the mid-section of a leaf where the larvae chewed through while the leaf was wrapped up inside the whorl.
By looking closely he has also found the actual corn borer larvae at work within the plant. So far, Greene has found larvae on non-GMO corn. He has not found corn borers in hybrids that carry the trait for protection against corn borer.
The first GMO trait widely introduced in the industry, many hybrids carry above-ground protection to corn borers. Many hybrids are triple stacks, with protection against corn borers and below ground protection against corn rootworms, plus resistance to glyphosate and/or Liberty herbicides.
However, you can also buy herbicides with glyphosate and/or Liberty resistance and just corn borer resistance, without below-ground protection against rootworms.
Customers who are growing non-GMO corn without protection against corn borers typically have a market where they can sell non-GMO corn for a premium, Greene says. He also notes that while he has found corn borers in plants and the shot-hole feeding that indicates corn borers are there, whether you see them or not, he has not seen enough damage to warrant treatment at this point.
It takes a fair level of damage before spraying for corn borers is justified based on whether you can preserve enough yield to cover the cost of the insecticide and the application by treating, he notes.