Impact of simulated Helicoverpa zea (Lepidoptera: Noctuidae) feeding in soybeans with determinate and indeterminate growth habits

Abstract

Helicoverpa zea (Lepidoptera: Noctuidae) injury to soybean (Glycine max L.) may result in yield loss by feeding on reproductive tissue. 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 soybean with indeterminate growth habits continue vegetative growth even after entering their reproductive stages. Management recommendations for H. zea in the southeastern US were developed from soybean varieties with determinate growth habits. The objective of this research was to understand the compensatory ability of these growth habits to H. zea feeding. We hypothesized that soybean with an indeterminate growth habit might have a greater ability to compensate yield components following H. zea feeding compared to determinate growth habits, as indeterminates typically flower for a longer time. We designed a field experiment comparing a single determinate and indeterminate soybean variety within the same relative maturity. We removed 0%, 50%, and 100% of reproductive tissue between pre-bloom and beginning pod stages (R1 to R3) to simulate H. zea feeding over two years. Yield components were collected to detect differences between growth habits. We found that indeterminate varieties showed greater compensation by adjusting pod type and seed weight, particularly under partial tissue removal. Indeterminate plants produced more one- and four-seeded pods, while determinate plants increased three-seeded pods. Total tissue removal reduced yield components, but moderate damage allowed for compensation. Differences may be driven by environment and should be tested across more varieties.