Arthropod pest management of Cannabis sativa (industrial hemp) in North Carolina

Observations during the North Carolina 2019 season suggest that Helicoverpa zea (corn earworm) and Chloridea virescens (tobacco budworm) were common in field-grown industrial hemp (Cannabis sativa) post flowering, and that Tetranychus urticae (two-spotted spider mite) occurred primarily in greenhouse production. Host suitability assays indicated that T. urticae and C. virescens can survive on industrial hemp under laboratory conditions. Controlled experiments looking at comparing individual plant versus pooled plot sampling methods as well as the effects of different arthropod feeding modes on cannabinoid concentration are underway. BaOx clones, one of the most commonly grown hemp varieties in North Carolina, were grown under greenhouse conditions. After flower initiation plants were treated as untreated control, mechanical damage (50%), C. virescens (10), Low T. urticae (200). Pre-infest and end samples were taken from each of the five treatments, with one replicate having both individual plant samples and one pooled sample. Single plant analyses were similar to pooled plot analyses except one, for single plants, Low T. urticae significantly affected THC (p < 0.0001). When looking at the pooled sample change over time THC and CBD increased more in C. virescens plants as compared to the Mechanical Damage Control (THC: p=0.0195; CBD: p=0.0249) and High T. urticae had a greater reduction than the Controls and Low T. urticae (THC: p=0.0003; CBD: p=0.00025).