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 corn borer, Ostrinia nubilalis (Hubner), in cor n stalks, and to examine the effect of primary tillage and flail mowin g of corn stalks on mortality of the overwintering population. Approxi mately 78% of the overwintering population was found in corn stalks wi thin 30 cm of the soil surface, and 25% within 7.5 cm. Most larvae fou nd 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 co in stalks after corn harvest reduced overwintering populations of Euro pean corn borer up to 85%. Primary tillage such as moldboard plowing o r chisel plowing in tile fall reduced overwintering populations. Mowin g corn stalks combined with primary tillage improved mortality. The hi ghest mortality was achieved by mowing corn stalks after harvest follo wed 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 gr eatest benefit. Moldboard plowing alone in the fall resulted in mortal ity of between 29 and 80% depending on whether plow slices were left s tanding or flipped over. Mowing before moldboard plowing added up to 1 0% mortality. Chisel plowing in the fall resulted in mortality of up t o 75%, whereas mowing before fall chisel plowing added up to 13% morta lity. However, if mowing in the fall preceded chisel plowing in the sp ring, >95% mortality was achieved.