ECONOMIC INJURY LEVELS FOR MANAGEMENT OF STALK BORER (LEPIDOPTERA, NOCTUIDAE) IN CORN

A computer program was developed to predict yield in corn (Zea mays L.) infested by stalk borer, Papaipema nebris (Guenee), on the basis of injury profiles for each leaf stage and regression models for predicting yield of individual plants. Yield losses caused by stalk borer declined as corn was attacked later in development. Once the stalk begins to elongate (6-leaf stage), the ability of the stand to tolerate stalk borer injury sharply increases. However, yield loss in 6- and 7-leaf corn was much greater under drought stress than when moisture was adequate. Yield losses for selected leaf stages were comparable to those reported for black cutworm, Agrotis ipsilon (Hufnagel), and European corn borer, Ostrinia nubilalis (Hubner). Predictions from this model were used to calculate economic injury levels for corn attacked at leaf stages 1-7 under adequate moisture and drought conditions. A management program, which incorporates larval sampling in noncrop areas and prediction of movement on the basis of degree-day accumulations, is presented.