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Ohio State University Extension

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1st Generation European Corn Borer Management in non-Bt Corn

European corn borer (ECB) was once our most important corn insect, but its population has decreased over the past 20 years, likely due to Bt-corn that provides excellent protection. For this and other various reasons, many farms have switched to corn that does not contain Bt proteins to control ECB and other caterpillar pests. Keep in mind that ECB is not an extinct species—we can find ECB still flying around. This year, we have seen ECB feeding in conventional corn.

ECB has 2 generations per year. Currently, we are seeing larval feeding on the leaves and in the whorl. Soon, and if not already, these larvae will tunnel through the stalk where they will usually continue to feed and pupate. Adults will emerge in late July-early August.

Growers of conventional corn should inspect their fields for the characteristic shot hole damage (see figure). If found, you may see larvae feeding in the whorl—you may need to pull the whorl out of a couple of damaged plants to check. Although challenging, larvae in the whorl that are in the 3rd instar or less (usually no bigger than 1/2 of an inch) are still vulnerable to insecticide application.

If the larvae are not in the whorl, they may have died, or worse, tunneled in the stalk. Look for the appearance of sawdust like frass, which ECB larvae leave on the outside while tunneling. Once they bore into the stalk, then control is difficult, if not impossible.

As a guide, we recommend treatment for 1st generation ECB when 75% -80% of the corn shows shot hole damage, and that larvae can be seen in the whorl (i.e. have not bored into the stalk). There are many chemicals that can control ECB (see our bulletin: https://agcrops.osu.edu/publications/control-insect-pests-field-crops-bulletin-545), although granular forms tend to be more effective than liquid.

Crop Observation and Recommendation Network

C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.