Hemp in breeding plots at UC Davis in late August 2019. (Charlie Brummer/UC Davis)
Hemp in breeding plots at UC Davis in late August 2019. (Charlie Brummer/UC Davis)

University of California Hemp Research Already Yielding Results

Hemp growing in breeding plots at UC Davis in September 2019. (Charlie Brummer/UC Davis)
Hemp growing in breeding plots at UC Davis in September 2019. (Charlie Brummer/UC Davis)

For the first time, researchers harvested an industrial hemp crop at a UC Agriculture and Natural Resources (UC ANR) research and extension center and at UC Davis this fall.

“It’s an interesting crop,” said UC Cooperative Extension specialist Bob Hutmacher. “There is a tremendous amount of research that can be done to understand its growth and best cultural practices, optimal planting dates either by seed or transplants, irrigation and fertilization management, and, particularly, to address pest and disease management.”

The research project is part of a two-location study, one at the UC West Side Research and Extension Center (WSREC) in Five Points, California, where Hutmacher is center director, and an identical companion study at the UC Davis farm headed by UC Cooperative Extension specialist Dan Putnam and professor and plant breeder Charles Brummer. Putnam, Brummer, and Hutmacher are Plant Sciences faculty at UC Davis.

These initial studies included a planting density by variety trial and a breeding observation block representing a wide range of genetics. The research was launched mid-summer this year after the 2018 Farm Bill declared that hemp should no longer be considered a controlled substance, but rather an agricultural commodity.

Industrial hemp can be produced for grain and fiber, however, many growers currently consider the most profitable component of the crop to be cannabidiol, or CBD, and related compounds. CBD is valued for its purported health benefits. It is said to reduce inflammation, pain, nausea, depression and anxiety, among other conditions.

Hutmacher said he and colleagues around the state are interested in learning about industrial hemp production opportunities, and feel there is a place for University of California (UC) research to support the fledgling industry. Already, there are some observations coming out of these small trials.

Pests on Hemp

“Some people believe that hemp is a pest- and disease-free plant. That’s not what we found,” Hutmacher said. “In the absence of suitable measures for control, corn earworms seemed to thrive in hemp, and did an astounding amount of damage to cultivars in our small plots.”

The scientists were forced to use a pesticide to control the pest and reduce damage to developing buds. The hemp produced in the trial will be destroyed after harvest data has been collected. The experience with corn earworm and other pest issues demonstrate that pest control will require significant study, particularly if a goal is to produce the crop organically.

“Markets for some industrial hemp products may require low pesticide residues. If hemp is produced organically, some preliminary observations this year suggest farmers will have to put a big effort into pest and disease control,” he said.

Corn ear worm. (Charlie Brummer/UC Davis)
Corn earworm on hemp. (Charlie Brummer/UC Davis)


Corn ear worm damage on industrial hemp buds. (Charlie Brummer/UC Davis)
Corn earworm damage on industrial hemp buds. (Charlie Brummer/UC Davis)


Breeding Hemp

Plant breeding can be another area of UC research. Hemp’s natural genetic variations produce plants that vary widely in growth habit, size, response to day length, and time to maturity. There are hemp cultivars that mature when the plant is 18 inches tall and others that shoot up 12 feet high at maturity. Hemp grown for CBD production from seed or as transplants can vary greatly in size and other characteristics, such as amount of branching and the number of flower structures per plant. Multiple plant and production system factors also will influence options for mechanical versus hand harvesting.

Another breeding concern for growers is producing a crop with economic levels of CBD or other compounds of commercial interest, while staying within regulatory limits for THC (tetrahydrocannabinol), the psychoactive compound found in marijuana, a related plant. According to the California Department of Food and Agriculture, an industrial hemp crop grown in the state may have no more than 0.3% THC when plant samples are analyzed.

“This will be a challenge for growers. You don’t want to risk too high a THC level,” Hutmacher said. “Farmers must test to make sure THC is at a level to meet regulations. If it’s too high, CDFA regulations would require the crop be destroyed.”

Working with UC breeders, integrated pest management scientists, agronomists, irrigation specialists and agricultural engineers, there should be good opportunities to finesse hemp production across California.

UC Cooperative Extension specialist Bob Hutmacher stands among tall cultivars of industrial hemp in September 2019.
UC Cooperative Extension specialist Bob Hutmacher stands among tall cultivars of industrial hemp in September 2019. (Dan Putnam/UC Davis, UC ANR)

Research center locations stretch from Holtville, in the low desert at the California–Mexico border, to Tulelake, just south of the Oregon border. Other centers ideal to answer hemp research questions include the UC Davis campus, the Hopland REC in Mendocino County, the Hansen REC in Ventura County, and the South Coast REC in Orange County.

For more information, contact Bob Hutmacher at 559-260-8957 or rbhutmacher@ucdavis.edu.

Additional Information on Cannabis and Hemp from UC Davis

  • Hemp Breeding and Seed Production: Two-day course, October 2019.
  • Plant Sciences website: UC Davis Cannabis and Hemp – Plants to Products Research.
  • UC Davis website: Cannabis and Hemp Research Center.
  • UC Davis partners with DEA-approved company to conduct cannabis research. August 2019.
  • Hemp as a California Crop: UC Davis partners in research agreement. March 2019.
  • Cannabis sativa: The plant and its impact on people – new graduate course at UC Davis. September 2018.

(Article by Jeanette Warnert, UCANR, reprinted from Green Blog. Additional information from Ann Filmer, Plant Sciences, UC Davis. October 31, 2019.)

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