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Hemp vs. marijuana: Cross-pollination concerns grow

We previously posted that Congress passed the Agriculture Improvement Act of 2018, also known as "The 2018 Farm Bill," which partly changed some restrictions on regarding industrial hemp.

With some federal restrictions lifted, hemp farming has been expanding; according to the advocacy group Vote Hemp, licensed acreage has quadrupled to 511,442 across 34 states in 2019.1 That said, industrial hemp farmers and marijuana farmers may be botanically at odds if their fields are located too close to each other: They may face cross-pollination. In this post we look at some concerns amongst farmers about potential cross-pollination of these plants.

Emerging Issues Weekly Digest

Industrial hemp farmers and marijuana farmers may be botanically at odds if their fields are located too close to each other: They may face cross-pollination.

What is industrial hemp?

Industrial hemp "is cultivated for use in the production of a wide range of products, including foods and beverages, cosmetics and personal care products, nutritional supplements, fabrics and textiles, yarns and spun fibers, paper, construction and insulation materials, and other manufactured goods." 7 U.S.C. § 5940, defines, in part, industrial hemp as "the plant Cannabis sativa L. [the same species of plant as marijuana] and any part of such plant, whether growing or not, with a delta-9 tetrahydrocannabinol [THC] concentration of not more than 0.3 percent on a dry weight basis." 2 The THC content of less than 0.3 percent found in industrial hemp products is reportedly low enough that there are no psychoactive effects associated with hemp consumption.3 

In a subsequent post, we also noted that CBD, the, non-psychoactive cannabinoid compound found in marijuana and hemp may have therapeutic effects. According to the Marijuana Business Daily, 84 percent of hemp farmers in 2017 were growing for the CBD industry.4

What is status of the new USDA regulations?

Lexology reported that the United States Dept of Agriculture (USDA) has recently published the interim rules titled "Establishment of a Domestic Hemp Production Program" (effective from October 31, 2019 to November 1, 2021) which partly describes how hemp production may be regulated at the federal level.5,6  Lexology noted that the rules do not prohibit states from enacting stricter laws or from prohibiting hemp production. The new regulation will reportedly "address procedures for collecting data on where hemp is grown or produced, testing THC levels, disposing of plants that test above the allowable THC level, licensing requirements, and handling violations."

What is the cross-pollination concern?

According to a Michigan University blog, since hemp and marijuana plants are members of the same species, they can pollinate each other, meaning the pollen from the male plant can pollinate the female.7  Per the blog, if this occurs with either plant, it could result in various problems for farmers: One study showed a 56 percent reduction in oils, either CBD or THC, if the female plants are pollinated. Therefore, both industries look to cultivate only female plants and try to remove male plants from farms as soon as possible. 

Unintended cross-pollination can reportedly occur when the pollen from the outdoor field of one plant blows in the wind to pollinate other fields. The distance between fields is thus critical to potentially mitigating unwanted pollination. The blog notes that experts have suggested 10 miles between fields as a distance to help prevent such cross-pollination. The blog explains that in Michigan it currently may be difficult to ensure any distance because although the state agencies that regulate marijuana and hemp record locations of these fields, they apparently do not coordinate to mitigate cross-pollination and the location information is not public, so farmers might have a difficulty even voluntarily trying to space fields far enough apart.

Cross-pollination is happening

That said, the Chicago Tribune has reported that Washington State Senate Bill 5276 was recently signed into law, and it removed, in part, a four-mile distance requirement between outdoor growers of hemp and marijuana.8 According to the Tribune, some farmers lamented the change, with one marijuana farmer estimating  "he will lose about $40,000 this year after his midsized, 600-plant farm was cross-pollinated by pollen from the male plants he said came from a neighboring hemp grower." The Tribune explains that the farmer will now have to sell his crop for extraction, which has a lower market value.

A related August 2019 Capital Press article explains that in Oregon, "[a] seed company is pursuing a lawsuit accusing nearby hemp growers of negligence, nuisance and trespass for pollination from a mixed crop of male and female plants."9  Per the article, if farmers grow hemp fiber and oilseed for crushing, they can mix male and female plants basically because they will eventually just cut down the plants. Such farms can expose nearby farms to the male pollen.

Per the Tribune, about 8 percent of the marijuana production in Oregon is estimated to be impacted by cross pollination, which can reportedly reduce the cannabinoid content of a field by about 1 percent.

Of interest, the Tribune notes that the USDA is supporting researchers at Virginia Tech who are developing wind-dispersed pollen prediction models partly by using drones to track how far pollen grains can travel. The researchers reportedly hope their work may support more appropriate recommendations for distances needed between farms to help prevent cross pollination.

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Christopher Sirota

Christopher Sirota, CPCU, is ISO Emerging Issues product development lead at Verisk. He can be reached at Christopher.Sirota@Verisk.com.


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  1. "Vote Hemp Releases 2019 U.S. Hemp Grower License Report Documenting Planned Hemp Cultivation In The U.S.," Vote Hemp, September 5, 2019, < https://www.votehemp.com/update/vote-hemp-releases-2019-u-s-hemp-grower-license-report-documenting-planned-hemp-cultivation-in-the-u-s/ >, accessed on June 30, 2021.
  2. "7 U.S. Code § 5940 - Legitimacy of industrial hemp research," Legal Information Institute, < https://www.law.cornell.edu/uscode/text/7/5940 >, accessed on June 30, 2021.
  3. Julie Thomson, "Here's Why Edible Hemp Will Never Get You High," Huffington Post, September 11, 2017, < https://www.huffpost.com/entry/hemp-seeds-thc_n_59b154a0e4b0b5e53104312e >, accessed on June 30, 2021.
  4. "New Washington state law worries marijuana growers over cross-pollination from hemp farms," Marijuana Business Daily, July 24, 2019, < https://mjbizdaily.com/cross-pollination-concerns-in-washington/ >, accessed on June 30, 2021.
  5. Nexson Pruet, "USDA Releases New Rules on Hemp Production," Lexology, November 12, 2019, < https://www.lexology.com/library/detail.aspx?g=4d7c427c-d68d-4b09-ba24-c11e1447100f >, accessed on June 30, 2021.
  6. "Establishment of a Domestic Hemp Production Program," United States Department of Agriculture, October 31, 2019, < https://www.govinfo.gov/content/pkg/FR-2019-10-31/pdf/2019-23749.pdf >, accessed on June 30, 2021.
  7. James DeDecker, "Weighing the risk of cannabis cross-pollination," Michigan State University, July 12, 2019, < https://www.canr.msu.edu/news/weighing-the-risk-of-cannabis-cross-pollination >, accessed on June 30, 2021.
  8. Bart Schaneman, "Marijuana, hemp cross-pollination a budding conflict," Chicago Tribune, November 15, 2019, < https://www.chicagotribune.com/marijuana/sns-marijuana-hemp-cross-pollination-20191115-kjeydmy6urbapdhxp36iyzryku-story.html >, accessed on July 6, 2021.
  9. Mateusz Perkowski, "Hemp boom spurs cross-pollination disputes," Capital Press, August 27, 2019, < https://www.capitalpress.com/state/oregon/hemp-boom-spurs-cross-pollination-disputes/article_efd1e99c-c903-11e9-8bdd-73e58f5946b5.html >, accessed on July 6, 2021.

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