Potential for Grain Sorghum as a Trap and Nursery Crop for <i>Helicoverpa zea</i> and Its Natural Enemies and Dissemination of <i>Hear</i>NPV into Cotton

Experiments were conducted in 2020 and 2021 in College Station, TX; Stoneville, MS; and Blackville, SC, to evaluate the potential of grain sorghum to serve as a trap crop for <i>Helicoverpa zea</i> (Boddie), a nursery crop for natural enemies of <i>H. zea</i>, and a source of <i>Helicoverpa armigera</i> nucleopolyhedrovirus (<i>Hear</i>NPV) for <i>H. zea</i> management in cotton. The experiments consisted of three treatments, including cotton-only, non-treated cotton–sorghum, and <i>Hear</i>NPV-treated cotton–sorghum. Variables, including percent injury to fruiting forms, parasitized <i>H. zea</i> larvae, egg density, <i>H. zea</i> larval density, beneficial arthropod numbers, and <i>Hear</i>NPV prevalence, were compared between the treatments. Growing cotton in an intercropping system with grain sorghum did not result in a consistent increase in <i>H. zea</i> control and beneficial arthropod density relative to the cotton-only treatment. Additionally, our results did not show sufficient evidence that grain sorghum interplanted with cotton can serve as a source of <i>Hear</i>NPV that can favor <i>H. zea</i> control in cotton. However, we found that, if maintained in the cotton canopy, <i>Hear</i>NPV may favor some level of <i>H. zea</i> suppression in cotton. Based on our <i>Hear</i>NPV infection analyses using PCR, chrysopids, coccinellids, pentatomids, reduviids, formicids, anthocorids, and spiders appeared to be carrying <i>Hear</i>NPV. The virus was detected consistently in specimens of coccinellids, pentatomids, and reduviids across both years of the study. We suggest that further investigation on virus efficacy against <i>H. zea</i> in cotton using the sorghum–cotton system as well as the ability of grain sorghum to serve as a <i>H. zea</i> trap crop and source of <i>H. zea</i> natural enemies be considered in future studies.