INJURY PROFILES AND YIELD RESPONSES OF SEEDLING CORN ATTACKED BY STALK BORER (LEPIDOPTERA, NOCTUIDAE)

The effect of feeding by the stalk borer, Papaipema nebris (Guenee), on the visible injury and grain yield of individual corn (Zea mays L.) plants, infested at various developmental stages, was evaluated experimentally from 1986 to 1988. Injury profiles differed by growth stage, with younger plants having a higher incidence of severe injury (dead heart, tillering, plant death). Plants attacked at the six-leaf stage or older were not as vulnerable to severe injury because tunneling occurred below the growing point. Grain yield, number of kernels per plant, and average kernel weight declined as the severity of injury increased. In 2 of 3 yr, plants assigned the same injury rating yielded more if the attack occurred earlier in development than later. In addition, uninfested plants in infested plots yielded more than uninfested plants in check plots. Plot yield losses seem to be moderated by the ability of uninfested or slightly injured plants to compensate for severe stalk borer injury. Regression models were developed to predict yield components for individual plants from injury rating and average rating of the plot.