Influence of hemp variety and fertilizer rate on populations of corn earworm, Helicoverpa zea, and plant characteristics

In recent years, legal boundaries surrounding industrial hemp, Cannabis sativa L., have been lifted allowing legal production, market development, and university research. The 2014 Farm Bill defined hemp to be grown as a legitimate crop by permitting production under a pilot program relationship with universities and state departments. In Tennessee, the 2018 Farm Bill fully allowed commercial hemp production directed by the Tennessee Department of Agriculture (TDA). In 2019, producer interests ignited with 3,957 growers licensed to manage more 20,639 hectares (approx. 51,000 acres) in Tennessee alone. Though fiber and seed have a role in the industry, most growers (ca. 98%) concentrated on CBD production because of the expected higher cash value potential/hectare. Introducing hemp as a monocrop system in this temperate region while researchers scramble to provide pest management strategies provided a perfect storm for hemp. Corn earworm, Helicoverpa zea (Boddie), is the most destructive insect pest in hemp across the country. This field and laboratory research focused on the influence of hemp variety and fertilizer rate on damage caused by corn earworm, and resulting plant characteristics. Variety and maturation rate were highly correlated to corn earworm larval damage on hemp. Fertilizer rates did not affect damage by corn earworm. CBD and THC concentrations varied among varieties. This poster will examine relationships among varieties, %CBD, %THC, yield, and corn earworm damage. Selecting later-maturing varieties may provide an important first step in an IPM plan to manage this destructive pest.