Effect of Mowing Corn Stalks and Tillage on Overwintering Mortality of European Corn Borer (Lepidoptera: Pyralidae) in Field Corn

Studies were conducted to determine the distribution of overwintering larvae of the European com borer, Ostrinia nubilalis (Hübner), in com stalks, and to examine the effect of primary tillage and flail mowing of com stalks on mortality of the overwintering population. Approximately 78% of the overwintering population was found in com stalks within 30 cm of the soil surface, and 25% within 7.5 cm. Most larvae found in stalks below the mower blades survived mowing. About 75% of the larvae in the stalks >7.5 cm were killed by the flail mower. Mowing com stalks after com harvest reduced overwintering populations of European com borer up to 85%. Primary tillage such as moldboard plowing or chisel plowing in the fall reduced overwintering populations. Mowing corn stalks combined with primary tillage improved mortality. The highest mortality was achieved by mowing corn stalks after harvest followed by moldboard plowing in the fall or chisel plowing in the spring. Mowing the stalks close to the ground (within 3 cm) resulted in the greatest benefit. Moldboard plowing alone in the fall resulted in mortality of between 29 and 80% depending on whether plow slices were left standing or flipped over. Mowing before moldboard plowing added up to 10% mortality. Chisel plowing in the fall resulted in mortality of up to 75%, whereas mowing before fall chisel plowing added up to 13% mortality. However, if mowing in the fall preceded chisel plowing in the spring, >95% mortality was achieved.