Evaluating the effects of terpene and cannabinoid variation in hemp (Cannabis sativa) germplasm on Helicoverpa zea oviposition and larval fitness

Helicoverpa zea Boddie (Lepidoptera: Noctuidae), commonly known as the corn earworm, is an economic lepidopteran pest of floral hemp Cannabis sativa L., (Rosales: Cannabaceae) grown for smokable flowers and cannabidiol (CBD) production. Following the re-legalization of hemp in the USA in 2018, hemp acreage in both field and greenhouse production increased rapidly. Research on hemp pest management strategies, including host plant resistance, is strongly needed. We evaluated seven floral hemp germplasm lines for potential host plant resistance to H. zea. Floral morphological traits and chemical composition (cannabinoids and terpenes) were evaluated to assess their role in antixenosis (oviposition performance) and antibiosis (larval performance), respectively. Moth oviposition performance was measured as the number of eggs laid per plant in no-choice assays, while larval performance was measured through survival and pupal weight. Results showed significant variation among germplasm. Specifically, the Blacklands Botanical CBG line was highly preferred for oviposition and had the lowest median larval survival. In contrast, the Wife/Cherry Wine line was the least preferred for oviposition with moderate larval survival. No relation between moth oviposition performance and larval fitness was observed. Total terpene content varied significantly among germplasm lines; still, these differences did not directly affect insect behavior and larval performance. However, higher CBD concentrations in plant flowers were associated with lower larval survival. Our findings indicate that both floral chemistry and morphology contribute to plant resistance to H. zea and can serve as a reference point for future research in breeding-resistant varieties.