By Susan Milius
November 19, 2018 at 7:00 am
VANCOUVER — Fields of hemp might become a late-season pollen bonanza for bees.
Industrial hemp plants, the no-high varieties of cannabis, are becoming a more familiar sight for American bees as states create pilot programs for legal growing. Neither hemp nor the other strains of the Cannabis sativa species grown for recreational or medicinal uses offer insects any nectar, and all rely on wind to spread pollen. Still, a wide variety of bees showed up in two experimental hemp plots during a one-month trapping survey by entomology student Colton O’Brien of Colorado State University in Fort Collins.
Bees in 23 out of the 66 genera known to live in Colorado tumbled into O’Brien’s traps, he reported November 11 at Entomology 18, the annual meeting of the U.S. and two Canadian entomological societies. O’Brien and his adviser, Arathi Seshadri, think this is the first survey of bees in cannabis fields.
“You walk through fields and you hear buzzing everywhere,” O’Brien said. He caught big bumblebees, tiny metallic-green sweat bees and many others clambering around in the abundant greenish-yellow pollen shed by the male flowers.
Bees need pollen to feed their young, and during the trap survey in August 2016, there weren’t a lot of other flowers blooming. Hardly anything is known about the nutritional qualities of hemp pollen for larval bees. Yet, commercial hemp plots may end up as rare food sources for pollinators in stressful times, O’Brien said. Honeybee health has faltered in recent years, and conservationists also worry about the fates of the many, less-studied wild bees. O’Brien urged crop scientists now developing the pest fighting strategies for outdoor hemp to be mindful of bee health.
Pest management techniques for hemp are still a work in progress. There are even questions about which insects are truly hemp pests, said entomologist Whitney Cranshaw, also of Colorado State. New potential menaces have arrived since the early 20th century, when farmers were growing hemp with very low concentrations of the psychoactive compound THC as a crop for fiber and other practical uses. Anti-drug legislation eventually made growing any cannabis forms illegal for decades in the United States.
The 2014 U.S. Farm Bill, however, differentiated between hemp with less than 0.3 percent THC by dry weight, and high-THC cannabis varieties of interest for recreational and medical use. This distinction has allowed states such as Colorado and Kentucky to set up programs for regulated legal growing in a push to revive the potentially valuable crop. But there are a lot of new questions about old plants.
A version of this article appears in the December 22, 2018 issue of Science News.
Citations
C. O’Brien and A. Seshadri. What is with all the buzzing? Exploring bee diversity in industrial hemp. 2018 ESA, ESC and ESB Joint Annual Meeting, November 11, 2018, Vancouver.
https://www.sciencenews.org/article/cannabis-fields-offer-late-season-pollen-source-stressed-bees
Sunday, November 11, 2018
09:50 AM - 10:05 AM
- Vancouver Convention Centre
- - Meeting Room 116/117
Colorado leads the nation in hemp (Cannabis sativa L.) production. As a versatile, multi-use crop, hemp is valued for fiber and seed. This study was conducted in Northern Colorado where hemp flowers between late July and late September. Dioecious and wind-pollinated, staminate hemp plants exhibit mass pollen shedding. At this point in the season many crops have completed bloom leading to a dearth of nutritional resources for pollinators. Thus, hemp becomes a valuable pollen source for foraging bees, giving it the potential to have a strong ecological value. We describe the diversity and abundance of bees in flowering hemp. We recovered 23 unique bee genera and a diverse number of other insects in hemp fields. Apis mellifera (38%), Melissodes (25%), Peponapis (16%) and Bombus (5%) accounted for over 80% of the total bee abundance in our samples. Hemp does not produce nectar, however staminate plants produce a wealth of pollen. Given the attractiveness of hemp to bees, we analyzed the nutritional content of hemp pollen in relation to honeybee health. With the proposed Hemp Farming Act of 2018, farmer interest in hemp cultivation is expected to grow. While the diversity of bees on flowering hemp indicates its ecological value, expanding hemp cultivation is likely to draw pests to the crop requiring pest control measures. Our documentation of bee diversity in hemp and the nutritional value of hemp pollen, supports the need for the development of integrated pest management practices that protect pollinators and maintain ecosystem functions.
Authors
- Colton O'Brien
- Colorado State University
- Arathi H. S. Seshadri
- Colorado State University