D3049: Impact of insect and mite feeding damage on industrial hemp cannabinoid profiles

Cannabis sativa, industrial hemp defined as < 0.3% total THC, is a specialty crop in the US, with particular interest among growers in North Carolina to replace tobacco production. Observations during the 2019 and 2020 NC hemp growing seasons suggest that Helicoverpa zea (corn earworm) and Chloridea virescens (tobacco budworm) were common in field-grown hemp post flowering, and Tetranychus urticae (two-spotted spider mite), Aculops cannabicola (hemp russet mite), and Polyphagotarsonemus latus (broad mites) were primarily greenhouse pests, but have been observed in field production. Lepidopteran injury can cause terminal growth of foliage and stalks as well as bud rot in flowers. Mite injury can cause cupping and yellowing of leaves, resulting in leaf drop, and reduced flower and resin production. Along with the physical damage caused by arthropod feeding, growers are concerned with the effects of feeding on cannabinoid concentrations. BaOx clones, a commonly grown hemp variety in NC, were used and grown under greenhouse conditions. To look at change over time pre-infest and end samples were taken from each of the treatments; untreated control, mechanical flower damage, C. virescens, H. zea, Low T. urticae, and High T. urticae. THC and CBD increased more in C. virescens plants as compared to the Mechanical Damage Control (THC: p=0.0195; CBD: p=0.0249). High infestation (~200) of T. urticae had a greater reduction in concentration than the Controls and low infestation (~50) T. urticae (THC: p=0.0003; CBD: p=0.00025). Results also showed that two-spotted spider mite density is strongly correlated with reduced CBD concentration.