Survey Helps UC  Understand Cannabis Production Challenges in State

By Patrick Cavanaugh, Editor

Results from a UC Cooperative Extension survey of registered and unregistered marijuana (cannabis) growers in California will help researchers, policy makers and the public better understand growing practices since cannabis sales, possession and cultivation first became legal for recreational use.

“This survey is a starting point from which UC scientists could build research and extension programs, if possible in the future,” said lead author Houston Wilson, UCCE specialist with UC Riverside. A report on the survey results was published in the July-December 2019 issue of California Agriculture journal, the research publication of UC Agriculture and Natural Resources.

Houston Wilson, UC Riverside Entomologist

The idea of the online survey, during the summer of 2018, was to characterize broadly the production practices that were being employed,” said Wilson

Wilson noted that since he is an entomologist, there were certainly questions about pest management, so the survey was more broad. “It included questions about style of production, plant density, harvest frequency, water use, diseases, and even labor and licensing,” Wilson said.

The survey was conducted by a collaborative group of scientists. Project co-authors were UC Berkeley visiting scholar Hekia Bodwitch, Nature Conservancy senior scientist Jennifer Carah, UCCE biocontrol specialist Kent Daane, UCCE natural resources specialist Christy Getz, UCCE climate and water specialist Theodore Grantham and UCCE land use science specialist Van Butsic. Daane, Getz, Grantham and Van Butsic are affiliated with UC Berkeley.

The survey went to numerous growers via large grower organizations that are present in California. There were more than 100 respondents, and the researchers were able to use that data to characterize some of the production practices.

“As an entomologist, I was interested in the pest management aspects, and we got a kind of array of different insects that growers are dealing with and how they’re dealing with it,” said Wilson.

UC is Restricted To Help Cannabis Growers

The big limitation that’s on the university right now is it’s ability to actually physically visit farms, and talk to growers, and collect insects and sample plant materials. It’s not legal for research institution because of the federal support that the university receives. “So a remote online survey, was the best approach that we found to do this, at least at this stage,” said Wilson.

We’ve shown the data to the grower groups that we’re in contact with, and for the most part they’ve agreed that that it matches what they’re seeing. “We don’t think it’s a really skewed dataset, but we certainly need more detail in each of those areas of emphasis,” said Wilson. “What I’d like to do now is figure out a way to actually collect insects from some of these cannabis operations to confirm or deny the pest species that were indicated by the survey.”

One way to do that is find some opportunities with grower collaborators to have them collect the insects themselves and then bring that back to researchers. “We’re allowed to handle the insects, but we certainly can’t have any plant material on campus right now,” Wilson said.

“Like any cropping system you’re going to have insect problems. Generally speaking, cannabis production takes place indoor and outdoor, and those are in and of themselves going to have different pest complexes and different management options available to them,” noted Wilson. “But again, this similarly applies to other crops that are grown in or outdoors. So there’s kind of gray literature or white literature, whatever you want to call it, about cannabis production and pest management in particular.”

There is cannabis production information in books and online forums that have been published by non-university personnel. “There’s some good information, and there’s a lot of misinformation. However many of these growers have a lot of experience as they they’ve been growing, in some of these areas, for over 40 years,” Wilson said.

Ironically, cannabis is seen as new crop for university researchers, as if it’s a new type of apple. “So in that regard, we’re just trying to characterize how the crop is produced, and find out what are some of the basic agronomic features of it, what are the pest pressures, and how would you manage that,” said Wilson.

“The fact that it’s been this underground production model for so long is that when we come into the situation, and in my interactions with growers to date, I immediately acknowledge that I understand that they have a lot of experience with this crop. And I think these growers have a lot of knowledge about agronomic features, including the entomology aspects of it,” said Wilson.

As for the future UC work in the cannabis world—it’s to be determined.It certainly a secondary if not tertiary objective for me, he said.I work in perennial orchards and vineyard, so cannabis is very much outside what I am focused on, he said.But there was an opportunity to do a survey and so we did it.

The article in the UC California Agriculture journal is comprehensive look at who is doing what in the state right now with cannabis production. “Our production survey was certainly front and center in there as a background piece. And there were other articles that were getting into a specific issue with labor, or licensing, or other areas. Water use is a huge issue, as it is with any crop in California,” said Wilson.

Wilson noted that if cannabis were to become legal at the federal level, you might envision a future where UC creates a position that includes cannabis or is even specifically focused on that in terms of agronomic issues.

Highlights of Survey Findings

  • Growing outdoors in open air with sunlight was the most common practice (41%). Twenty-five percent of growers combined outdoor and greenhouse production. Just 10% said they grow the crop entirely within greenhouses.
  • Total yield per plant varied by growing location. Outdoor crops yielded on average 2.51 pounds per plant (about 40 ounces per plant), greenhouse crops yielded about 10 ounces per plant, while plants grown indoors with artificial light averaged about 3 ounces per plant.
  • The average growing season for outdoor growers was 190 days and they harvested one crop per year.
  • In the fall of 2017, the average cannabis sales price was $853 per pound for flowers and $78 per pound for leaves and other non-flower parts.
  • The respondents reported using no synthetic pesticides in their cultivation of the crop, suggesting reliance on organic pesticides, biologicals and biocontrol.
  • Most growers reported that groundwater was their primary water source for irrigation. Of those, 97% of the water extraction happened from June to October. Many growers said adding water storage was either cost prohibitive or limited by regulatory constraints.
  • Growers reported using more than 30 different soil amendments and foliar nutrient sprays. The most common was organic fertilizer, followed by composts and various animal manures and meals, compost tea and worm castings.
  • Growers are dealing with 14 different insect pests, 13 diseases and nine vertebrate pests, including gophers, mice, rats, deer and wild boars.
  • Powdery mildew was the most commonly reported disease, and mites, thrips and aphids were the most commonly reported insect pests.
  • Growers who hired laborers for harvest paid a per-pound piece rate from $50 to $200. The growers who hired seasonal hourly workers offered a starting pay of $15 to $20 per hour.