Hemp (Cannabis sativa L.) is now being grown within the United States over a much broader geographic area and for different uses than during its last period of significant production that ended after World War II. Within the past 3 yr, a large number of arthropod species have been documented to feed on hemp in the United States. Among key pest species, corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), has demonstrated greatest potential for crop injury, being particularly damaging to flower buds. Hemp russet mite, Aculops cannibicola (Farkas), and cannabis aphid, Phorodon cannabis Passerini, are the two species observed most damaging among those that suck plant fluids. Eurasian hemp borer, Grapholita delineana Walker, is widely present east of the Rocky Mountains and appears to have potential to significantly damage both flower buds and developing seeds. Numerous species of caterpillars, grasshoppers, and beetles chew hemp foliage; the severity of these defoliation injuries appears to be minimal, but needs further study. Similarly, numerous seed feeding hemipterans, most notably stink bugs and Lygus bugs, are regularly found in the crop but injury potential remains unclear. Some preliminary efforts have been made to develop integrated pest management strategies for these insects, particularly for corn earworm. Future research can be expected to rapidly resolve many of the data gaps that presently restrict advancing pest management on the crop. However, a major confounding issue involves the use of pesticides on hemp. Federal agencies have not yet provided clear direction on this issue, and regulatory decisions have subsequently devolved to the states.

Corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae), has emerged as an injurious insect pest to hemp, Cannabis sativa L., a crop newly reintroduced to the United States. Growing hemp presents a potential alternative economic opportunity for farmers but can be challenging with a market that is unstable and just developing. One of the most notable production challenges is managing corn earworm, an insect pest that is particularly damaging when it feeds on flower buds produced in cannabinoid varieties, creating extensive bud tunneling and wounds that allow entry of pathogens that can aid development and presence of bud rot. Damage to seeds is of lesser concern in hemp cultivars grown for grain and minimal risk is associated with hemp grown for fiber. Our ability to research hemp has only recently been allowed as production was largely suspended following World War II and, as such, there has been limited opportunity to develop information for empirically-based pest management recommendations. Further complicating development of integrated pest management (IPM) strategies are regulatory challenges associated with providing registration support to add hemp to pesticide labels, as it was not formally recognized as a crop by U.S. regulatory agencies until late 2019. Research needs and challenges to develop effective IPM programs for corn earworm on hemp are discussed here.

A SURVEY OF THE ARTHROPOD FAUNA ASSOCIATED WITH HEMP (CANNABIS SATIVA L.) GROWN IN EASTERN COLORADO Industrial hemp was found to support a diverse complex of arthropods in the surveys of hemp fields in eastern Colorado. Seventy-three families of arthropods were collected from hemp grown in eight counties in Colorado in 2016Colorado in , 2017Colorado in , and 2018. Other important groups found in collections were of the order Diptera, Coleoptera, and Hemiptera. The arthropods present in fields had a range of association with the crop and included herbivores, natural enemies, pollen feeders, and incidental species. Hemp cultivars grown for seed and fiber had higher insect species richness compared to hemp grown for cannabidiol (CBD). This observational field survey of hemp serves as the first checklist of arthropods associated with the crop in eastern Colorado. Emerging key pests of the crop that are described include: corn earworm (Helicoverpa zea (Boddie)), hemp russet mite (Aculops cannibicola (Farkas)), cannabis aphid (Phorodon cannabis (Passerini)), and Eurasian hemp borer (Grapholita delineana (Walker)). Local outbreaks of several species of grasshoppers were observed and produced significant crop injury, particularly twostriped grasshopper (Melanoplus bivittatus (Say)). Approximately half (46%) of the arthropods collected in sweep net samples during the three year sampling period were categorized as predators, natural enemies of arthropods. These findings are of significance considering the expanding cultivation of hemp both within the region of study and across the United States. A website developed to extend the information developed in this project has been accessed over 20,000 times in 28 months, indicating there is wide interest in this subject area.iii ACKNOWLEDGEMENTS I wish to thank my family and friends, for without them I would not have had the support, which I needed to complete this degree. I would like to acknowledge the substantial funding provided by the Western Region IPM Center and the CSU Experiment Station. Thank you to the participating farmers, production farms, and research stations that permitted us to sample arthropods from their facilities across Colorado. Thank you to the Fat Pig Society, Colorado Cultivars, and the Colorado Department of Agriculture for providing resources to conduct local hemp trials, insect collection, and analysis. Thank you to all the lab members: