D3267: Simulating damage by Helicoverpa zea (Lepidoptera: Noctuidae) in soybeans in the southeastern

Helicoverpa zea (Lepidoptera: Noctuidae) injury to soybean (Glycine max L.) may result in yield loss. To combat these losses, growers follow economic thresholds to establish the economically ideal time to spray pesticides. Soybean varieties are classified based on their morphological growth habit, which can be determinate or indeterminate. In varieties with a determinate growth habit, the onset of reproductive growth results in the termination of vegetative growth. While varieties with indeterminate growth habits continue reproductive stages before they terminate vegetative growth. Economic thresholds for H. zea in the Southeastern were developed from soybean varieties with determinate growth habits. The objective of this research is to determine if the current H. zea economic thresholds are relevant for both soybean growth habits. We hypothesized that soybean varieties with an indeterminate growth habit might compensate better for yield and yield component by H. zea injury when compared to varieties with determinate growth habit because indeterminate soybeans typically flower for a longer period. To test this hypothesis, field experiments were designed during the 2020 and 2022 seasons in North Carolina. After that, we compared soybean growth habits and determine if compensation mechanisms are the same when experiencing different levels and duration of H. zea feeding pressure. These results will support our understanding of the economic threshold for indeterminate and determinate soybeans and help stimulate the adoption of Integrated Pest Management (IPM) in the United States.