Persistence of <i>Helicoverpa armigera</i> nucleopolyhedrovirus on soybean foliage and activity against <i>Helicoverpa zea</i> (Lepidoptera: Noctuidae) larvae

Helicoverpa armigera Nucleopolyhedrovirus (HearNPV) is an insect virus in the family Baculoviridae and is a commercial biological pesticide to control Helicoverpa zea (Boddie). HearNPV offers potential benefits, including host specificity, economic affordability, and the ability to create epizootics. A disadvantage of HearNPV is ultraviolet light degradation. This study was conducted to determine the activity of HearNPV at different time intervals and whether a molasses-based surfactant would increase mortality of H. zea larvae. leaf samples were collected from the field at different time intervals following application. Susceptible stage (≤2nd instar) larvae were allowed to feed on treated leaf tissue, and artificial diet overlayed with rinsate from leaf tissue. Mortality was rated at 5, 7, and 12 d after exposure. In the current studies, HearNPV (with or without surfactant/feeding stimulant) resulted in ≥50% mortality of H. zea out to ca. 48 and 24 h, respectively, at 12 d after infestation. Adding the surfactant/feeding stimulant rarely increased larval mortality. Similar results were observed with the 2 bioassay methods at 7 and 12 d after infestation. The short residual of HearNPV could be problematic in situations where oviposition occurs over an extended period of time (>3 to 4 d). Also, the utility of HearNPV can be diminished if multiple pest species are present in the field at the same time.