A UC Cooperative Extension survey of California registered and unregistered marijuana growers 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, UC Cooperative Extension 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.
“I'm there, I'm seeing it. I wanted to know more about this,” Wilson said. “To me, it's a new crop. We've never studied it.”
In 2016, when legalization was in the works, Wilson decided to conduct a survey to better understand the scope of cannabis production in California. A year later, Wilson took a position with the Department of Entomology at UC Riverside as an orchard/vineyard IPM Cooperative Extension Specialist based at the UC Kearney Agricultural Research and Extension Center. He maintained his interest in cannabis and continued to lead the survey project and analyze the data.
The new research report is part of a growing body of knowledge about an industry that represents an estimated $10 billion in retail sales— likely the most valuable of all crop sectors in the state, but largely a mystery to scientists, regulators, growers and civic leaders. Cannabis production has not been widely researched in California because of its legal status before Proposition 64 passed in 2016 and went into effect Jan. 1, 2018.
Under federal law, cannabis remains illegal.
“Since UCCE is federally funded, and cannabis is not legal at the federal level, we cannot conduct any research that has potential to increase yield, improve quality or profitability,” said Robin Sanchez, UC ANR attorney and interim director of administrative policies and business contracts. “We are very careful to conduct research only about its scope and impact, but not production practices.”
Wilson and his colleagues gathered the information in July 2018 from 101 growers who responded to an online survey. Survey questions focused on farm size, operational features, pest and water management, labor, farm revenue and grower demographics. Respondents were recruited by 15 cannabis grower organizations, who together were able to supply approximately 17,500 contacts.
The respondents were aged from 34 to 72, with 69% male and 29% percent female. Two-thirds were married or living with a partner. More than half had household annual incomes from $50,000 to $99,000; and about 10% from $100,000 to $200,000. Thirty-four percent of growers earned 80 to 100% of their annual gross income from cannabis, while 33% reported no income from cannabis at all.
Most of the respondents produce cannabis in Humboldt, Mendocino and Nevada counties – 55% combined. The rest hailed from 12 other California counties, the furthest south in Los Angeles, and one respondent from Josephine County in Oregon.
Of the growers who responded to the survey, 74% were classified as small-scale growers because their farms were sized at 10,000 square feet or less. The rest were almost evenly divided as medium (10,000 to 20,000 square feet) or large. The majority of respondents (53%) reported that they had not applied for a state license to grow cannabis.
Highlights of 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.
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.
In 1953, amid reports that cannabis was growing around San Mateo County, the local sheriff's office and the UC Agricultural Extension Service in Half Moon Bay issued a booklet entitled Identify and Report Marihuana. The booklet envisioned “total eradication” of cannabis. The authors couldn't have imagined that, in 2017, the San Mateo County Board of Supervisors would pass an ordinance allowing greenhouse cultivation of cannabis in the county's unincorporated areas.
A lot can happen in 60-plus years — such as voter approval of Proposition 64, the 2016 ballot measure that altered California law to allow the recreational use of cannabis by adults.
That said, federal restrictions still inhibit many aspects of research (see page 104 for more detail). Cannabis research is also inhibited by funding constraints. The $10 million in annual research funding that Proposition 64 allocated to California universities has not begun to flow, and the Bureau of Cannabis Control — the entity responsible for disbursing the money — reports that it is still establishing guidelines for doing so.
Despite these obstacles, UC cannabis research in the legalization era is well underway, as attested by this special issue of California Agriculture. The research articles presented here fall into three broad categories — research into cannabis production, into the economics of the cannabis industry in California and into the social and community impacts of cannabis. The three articles focused on cannabis production include the results of the first known survey of California cannabis growers' production practices, by Wilson et al. (page 119). In the article “Characteristics of farms applying for cannabis cultivation permits” (page 128), Schwab et al. combine data on cannabis farms with information about applications for cultivation permits, establishing that, of farms within the dataset, those seeking permits tended to be larger and to have expanded faster than other farms. And on page 146, Dillis et al. analyze data submitted to the regional water quality control board to characterize the water sources used by cannabis cultivators in the Emerald Triangle region (Humboldt, Mendocino and Trinity counties).
Articles focused on the economics of the cannabis industry include a study by Goldstein et al. (page 136) analyzing online retail prices for cannabis flower and cannabis-oil cartridges as changes in regulation and taxation have taken effect in recent years. Valdes-Donoso et al. (page 154) analyze data from sources including California's cannabis testing laboratories to estimate the cost per pound of testing under the state's regulatory framework.
Four articles explore the social and community impacts of cannabis production. On page 161, Valachovic et al. report the results of a survey of timberland and rangeland owners in Humboldt County, who shared their experiences with the rapid expansion of cannabis production in their region and its attendant social, economic and environmental challenges. LaChance (page 169) interviewed noncannabis farmers, ranchers and others across Humboldt, Mendocino and Sonoma counties, eliciting their views on issues such as increased land prices amid cannabis legalization. For the article “Growers say cannabis legalization excludes small growers, supports illicit markets, undermines local economies” (page 177), Bodwitch et al. surveyed cannabis growers to gain insight into their experiences with the state's system for regulation of commercial cultivation. Finally, on page 185, Polson and Petersen-Rockney employed ethnographic methods to study cultivation regulations in Siskiyou County and their effects on the county's Hmong-American community. The special issue was conceived by Van Butsic and Ted Grantham — UC Cooperative Extension (UCCE) specialists based at UC Berkeley — and Yana Valachovic — a UCCE forest advisor and director for Humboldt and Del Norte counties. Butsic, Grantham and Valachovic developed the issue in collaboration with Daniel Sumner, a UC Davis professor of agricultural economics and director of the UC ANR Agricultural Issues Center, and with the staff of California Agriculture.
Before the San Joaquin Valley was cultivated, vast grasslands stretched from the Sierra to the Coast Range with soil that contained significant organic matter – a diversity of live and dead plant material and microbes that are key to soil health.
Tilling the soil for farming exposed it to air and allowed the organic matter to oxidize, releasing greenhouse gasses and reducing organic matter to about 1 percent of soil volume. UC Agriculture and Natural Resources research has shown that soils with low organic matter inhibit water infiltration, nutrient cycling, biological diversity and carbon sequestration.
But techniques have been developed to return soil to a more natural, more healthful state.
Farmers, students, researchers and community educators gathered at Gary and Mari Martin's farm in Mendota Sept. 13 to share ideas and strategies for extending information to the greater farming community that will increase adoption of conservation agricultural practices that reduce greenhouse gas emissions from farmland and at the same time improve soil health.
For two years, the Martins have opened their farm to research led by UC Cooperative Extension cropping systems specialist Jeff Mitchell. For the project, UC Davis doctoral student Geoff Koch is studying soil health indicators and greenhouse gas emissions at the Martins' farm and at the UC West Side Research and Extension Center, where plots have been cultivated using traditional methods and conservation practices side by side for 20 years.
Expanding the use of conservation agricultural practices is not limited to Central California.
“Our government endorses these principles of soil health,” Mitchell said. “It's part of a national campaign aimed at improving the health of our country's soils.”
- Minimize soil disturbance
- Emphasize biodiversity
- Keep living roots in the soil
- Keep soil covered with plants and plant residues at all times
Employing these techniques in the research project at the West Side Research and Extension Center for 20 years has shown that annual cover cropping has added 37 tons of organic matter per acre to the soil, captured 15 tons of carbon per acre and used only about 12 inches of water per acre.
At the workshop, three University of California Cooperative Extension (UCCE) climate-smart educators invited farmers to contact them for assistance in applying for state funds they can use to implement climate-smart farming practices.
Climate-smart educator Emily Lovell said the California Department of Food and Agriculture's State Water Efficiency and Enhancement Program (SWEEP) pays up to $100,000 to improve irrigation efficiency, reduce water use and reduce greenhouse gas emissions. Farmers can use the funding to, for example, convert to drip irrigation systems, install moisture sensors or set up a weather station.
Lovell said it is a competitive and complex application process.
“We help with the applications,” she said.
Climate-smart educator Shulamit Shroder described the CDFA's Healthy Soils Program (HSP), which incentivizes farmers with up to $75,000 to implement such practices as planting cover crops, using no-till or reduced tillage techniques, applying mulch or compost, or planting hedgerows. The applications are due in February 2020.
For more details on the CDFA Climate Smart Agriculture programs and for technical assistance on applying, contact a local UCCE climate-smart educator.
Californians love their oak trees. During vineyard development, Central Coast grape growers often feel compelled to leave an old iconic oak standing, even if it ends up right in the middle of their vineyard. While driving through the Central Coast, it's not unusual to see the pattern of vineyard rows broken by a majestic oak tree. Aside from their beauty, what are some of the ecosystem services that these majestic trees provide?
To understand the potential value of remnant oak trees for insectivorous bats, the researchers placed microphones to detect bat calls within 14 Central Coast vineyards. The recordings revealed 11 species of insectivorous bats foraged within the vineyards and bat foraging activity was 1.5 times greater at the trees compared to open, tree-less areas within the vineyard. And the bigger the tree, the bigger the number of bats it attracted.
“The study results suggest that the large oak tree in my vineyard not only increases the beauty and biodiversity of the agricultural landscape, but also attracts insect-eating bats that can provide natural pest control—a win-win,” said grape grower Jerry Reaugh, who cooperated with the researchers.
Tietje hopes that the free insect-reduction services provided by bats will increase grape growers' incentive to manage and maintain the trees, and even to plant new oak trees in suitable areas around their vineyard, in mutual benefit to both agriculture and biodiversity.
“In addition to their value for insectivorous bats, remnant trees maintain bird and insect diversity by providing food, habitat, cover and stepping stones that facilitate the movement of wildlife within agricultural landscapes,” said Tietje.
This study comes at a time when declining blue oak and valley oak populations are of great concern.
“We hope the study will increase awareness of these beautiful and beneficial trees and make the case for conservation and restoration,” Tietje said. “Preserving and enhancing biodiversity in the midst of climate change is key to ensuring resilience in our landscapes and communities.”
Last May, a Turlock almond grower noticed nearly all the nuts on a row of trees in his orchard had fallen to the ground.
“It looked like we shook this row,” he said. “I was scared. I thought the whole orchard was going to go.”
He called UC Cooperative Extension.
UCCE Integrated Pest Management advisor Jhalendra Rijal, who serves Stanislaus, San Joaquin and Merced counties, determined the cause was an infestation of brown marmorated stink bug (BMSB), an invasive pest from Asia. For years, BMSB had only been found in urban areas of California – most notably a 2013 infestation in midtown Sacramento.
With few natural predators and a wide host range – including apples, pears, cherries, corn, tomatoes, grapes and a variety of landscape trees – the population eventually moved into agricultural areas, first appearing in crops in 2016 in Stanislaus County. Rijal has been doing BMSB research since then.
Rijal hosted a gathering of farmers and pest control advisers Aug. 13, 2019, in the Turlock almond orchard to give them a first-hand view of the pest and the problems it causes.
BMSB are hard to find in orchards. They lay greenish colored eggs on the underside of leaves, typically in a cluster of 28 eggs. The majority of damage is caused by adults, which sting the hull with a needle-like mouth part to get to the nut. The sting can even penetrate the almond's hard shell when the fruit is mature.
Globs of clear sticky sap appear on the damaged almond hulls, typically indicating nut loss inside. Early season (March-April) infestation leads to the most severe yield loss when the nuts drop to the ground. The best way to confirm the damage is caused by BMSB is to use a trap.
“I recommend growers and pest control advisors put BMSB traps in orchard edges if they suspect BMSB damage or if the orchard is located near potential overwintering structures or host crops,” Rijal said. “BMSB are good flyers and active throughout the season, damaging nuts from April through the fall. But the most substantial damage happens in the spring through early summer."
If the orchard is close to BMSB-favored host plants, more damage is seen. A particularly troublesome neighbor plant is tree-of-heaven.
“Tree-of-heaven is a magnet for BMSB,” Rijal said, pointing to an abandoned farmhouse site on an adjacent property. “Tree-of-heaven has a nice fruiting structure that can support a lot of BMSB.”
Also an Asia native, tree-of-heaven was brought to California by Chinese immigrants during the Gold Rush. The roots, leaves and bark are used in traditional Chinese medicine. But its rapid growth and ability to clone itself to develop thick groves make it a noxious weed.
BMSB isn't a serious pest in its homeland because it is controlled by a natural enemy. Charles Pickett, the California Department of Food and Agriculture biological control scientist, shared a mounted sample of a Samurai wasp from Asia, Trissolcas japonicus, which lays its eggs in BMSB eggs.
“The parasite attacks most of the eggs in the field in eastern Asia,” Pickett said. “It's our goal to release the wasp in California. We first need a special permit to make sure it won't harm our environment and doesn't attack any beneficial stink bugs.”
The Samurai wasp has already found its own way to some BMSB infestation sites in the Eastern U.S. and in Los Angeles.
“We hope to someday release the parasitic wasp,” Pickett said. “It won't eradicate BMSB, but it will help.”