Bee diversity and abundance on flowers of industrial hemp (Cannabis sativa L.)

Highlights: • Industrial hemp cultivation is gaining popularity and its prolific pollen production may provide major ecological benefits. • Bee pollinators continue to face challenges making it crucial to develop agroecosystem practices that can sustain bees. • Industrial hemp can play an important role in providing sustained nutritional options for bees during the cropping season. • We report 20 different genera of bees on flowering hemp demonstrating that hemp in the agroecosystem supports pollinators. • This knowledge of bee diversity on hemp reiterates the need for integrated pest management as pests become common on hemp. -- Abstract: Industrial hemp, (Cannabis sativa L.), one of the earliest crops spun for fiber, is now used for a variety of commercial products including paper, textiles, clothing, biodegradable plastics, biofuel, food, animal feed etc., all of which are derived from hemp fiber or seeds. Being wind pollinated, dioecious and staminate hemp plants produce large amounts of pollen that are attractive to bees. Hemp flowering in northern Colorado, where this study was conducted, occurs between the end of July and the end of September. This time period coincides with a dearth of pollinator-friendly crop plants in the region, making hemp flowers a potentially valuable source of pollen for foraging bees. Here we present the diversity and abundance of bees collected in the fields of flowering hemp. A total of 23 different genera of bees were collected of which the European honeybee, Apis mellifera at 38% of the total abundance was the most dominant followed by Melissodes bimaculata at 25% and Peponapis pruinosa at 16%. These three genera made up nearly 80% of the total abundance. While hemp does not produce any nectar, the pollen rich nature of the flowers can make hemp an ecologically valuable crop. As cultivation of hemp continues to expand, we expect insect pests on hemp to also become prevalent. Our results documenting bee diversity in flowering hemp provides the impetus for the development of integrated pest management plans that protect pollinators while controlling pests.