By Scout Nelson
European corn borer caterpillars have recently been found in several conventional corn fields across South Dakota. These pests are being spotted in the whorl and upper stem of the plants. A common sign of their presence is a straight line of small holes in the upper leaves, often called “shot-hole injury.” These marks appear when caterpillars feed on leaves while they are still curled inside the whorl.
In South Dakota, there are two main populations of European corn borer. The northern areas usually have one generation per year, while southern areas often have two generations. Current damage reports are coming from southern regions where the pest has two life cycles annually.
Scouting for these caterpillars takes time and care. Farmers should inspect 20 plants from five different spots in each field, checking a total of 100 plants. If leaf damage is visible, the whorl and upper stem should be cut open to find and count the caterpillars. Their location in the plant is important for deciding control actions.
Although the European corn borer is less of a problem now due to corn hybrids, it still affects conventional corn fields. Without control measures, yield losses can range from 2% to 6% per plant, and in some cases, reach 12% when multiple caterpillars feed inside the same stem.
Photo Credit: gettyimages-dszc
Categories: South Dakota, Crops, Corn