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Agronomic Crops Network

Ohio State University Extension


Scout Corn for Western Bean Cutworm and Western Corn Rootworm

As we are entering tasseling and pollination for most of our corn, there are two insects that we should watch out for.  However, both need to be scouted before tank mixing an insecticide with a fungicide spray gives a good return.

 First, the amount of western bean cutworm adults in our traps is still on the rise, although we have probably reached peak flight (we won’t know for sure until the numbers go down). This is the time period when producers will want to scout for egg masses on the upper 2-3 leaves.  Remember that economic threshold is only 5-8% of corn with egg masses. Although we have not yet had economic damage from WBC, it is still important to look for the presence of eggs before any applications should be made.

 Second, growers may be seeing more western corn rootworm adults. For the past few years, we haven’t had to deal much with this pest, but we have received a fair amount of calls regarding leaf stripping and the potential for silk clipping. Both types of damage on corn are rare for Ohio.  For leaf stripping, this is usually not economic, but could be an indication of population sizes the following year. 

There are a few considerations before spraying to prevent silk clipping. First—silks must still be viable, in other words have not begun to turn brown; second—5 or more beetles per silk mass must be present; third—silks are being clipped to less than 1/2 inch. If all three of these conditions are met, control may be needed.  

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.