Predicting infestations of corn earworm (Helicoverpa zea) in sweet corn based on pheromone trap catch, plant stage and environmental factors

Agricultural insect pests are difficult to manage without close consideration of their interactions with host plants and the environment.  Helicoverpa zea (Lepidoptera:Noctuidae) is a caterpillar pest of sweet corn (Zea mays var 'saccharata') that causes significant yield reduction.  IPM practices first implemented in the late 1980's utilize male pheromone trap catches as a basis for insecticide treatments, but have not adequately minimized H. zea damage in recent years. Studies suggest that silking corn is very attractive to H. zea oviposition and that poor timing of  insecticide treatments can result in increased damage.  To test the effect of timing sprays, treatments targeting different phases of silk maturity were used, followed by damage evaluations at harvest.  In addition, pheromone trap catches and environmental variables were used as components in a multivariate analysis.  Results demonstrated that pheromone trap catch alone was not a good predictor of damaged ears.  Including silk phase, lunar phase, and precipitation significantly increased the prediction of damage.  This research demonstrates the importance of considering pest biology, plant growth and environmental conditions in developing sound IPM practices for the 21st century.