By Scout Nelson
Common stalk borers are occasional pests that can cause serious damage to young corn plants, especially in fields located next to grassy roadsides, waterways, or field borders. While infestations are usually limited to the first few rows of corn, unmanaged populations can reduce plant stands and affect crop development.
Adam Varenhorst, Associate Professor and SDSU Extension Field Crop Entomologist, along with Philip Rozeboom, Patrick Wagner, and Brad McManus, highlighted the importance of identifying and managing common stalk borers before significant damage occurs. Their work helps producers understand pest behavior and improve management decisions.
Adult common stalk borers are small brown moths with gray to brown wings and small white spots. The caterpillars are easier to identify because they have orange heads with black side stripes. Younger caterpillars also have a distinctive purple-brown band behind their legs. Fully grown caterpillars can reach 1½ to 2 inches in length.
Common stalk borers produce one generation each year. Adult moths emerge between August and October and lay eggs on dead grasses and other vegetation. The eggs survive winter and hatch in late spring. Young caterpillars feed on weeds and grasses before moving to larger plants such as corn.
Damage is most common when corn is in the VE through V5 growth stages. Caterpillars feed on leaves, creating ragged holes and leaving sawdust-like material around feeding sites. More serious injury occurs when they tunnel into stalks. This can slow plant growth, reduce pollination, create smaller ears, and sometimes cause “dead heart,” where the plant stops growing and dies.
Management focuses on prevention and early action. Controlling grasses near field margins during fall or late winter helps reduce egg-laying sites. Planting corn early can also lower risk because larger plants tolerate feeding better. Burning grassy areas during late winter may destroy overwintering eggs.
Photo Credit: gettyimages-dszc
Categories: South Dakota, Crops, Corn, Weather