“Without federal coordination, HLVd has been able to spread rapidly to cannabis cultivation sites across the United States since it was first detected in cannabis plants in California in 2019.”
By Margo Wilkinson Smith and Amy Rubenstein, Dentons
A hop latent viroid (HLVd) is spreading rapidly across cannabis plants, posing a serious and ongoing threat to cannabis cultivators. Unfortunately for cannabis cultivators, there has been no coordinated federal or state endeavor to address HLVd in cannabis plants.
In general, the federal government is responsible for responding to widespread crop diseases and viroids to treat or limit the spread of such diseases in crops across the country. Specifically, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) works cooperatively with state departments of agriculture and other government agencies to target, manage and eradicate (where possible) specific pests and diseases.
APHIS could assist with HLVd. However, in stark contrast to the government’s active involvement with hemp farmers, APHIS typically does not provide information about or regulate diseases that specifically affect cannabis plants—either because of federal prohibition or because the federal government does not see cannabis as an “agricultural interest” (although the Department of Health and Human Services (HHS) has recommended to the Drug Enforcement Administration (DEA) rescheduling cannabis as a Schedule III drug under the Controlled Substances Act).
Without federal coordination, HLVd has been able to spread rapidly to cannabis cultivation sites across the United States since it was first detected in cannabis plants in California in 2019: A 2021 survey found that 90 percent of the cannabis cultivation sites surveyed in California had at least some infected plants and that about 30 percent of the plants in sites surveyed with HLVd showed viroid symptoms. More recently, experts have estimated that between 25 percent and 50 percent of all U.S. and Canadian cannabis plants have HLVd.
While HLVd has no known effect on human health, it can reduce weight, yields and final production. Current estimates suggest that this “Dudding Disease” can reduce the production of cannabinoids like tetrahydrocannabinol (THC) and cannabidiol (CBD) by 40 percent to 50 percent. Such a decrease in production reduces the value of harvests and results in significant financial losses for cannabis cultivators, with one study estimating an annual $4 billion in lost yields.
How Is HLVd Spreading So Rapidly?
As its name suggests, HLVd is latent, so infected plants may not show physical viroid signs. (Those plants that do have physical signs of the viroid may have stunted growth, small leaves and brittle stems in the vegetative state, or a reduction or underdevelopment in trichomes, a muted smell or smaller buds at the flowering stage.)
Because infected plants can show no symptoms—and regular testing remains uncommon—experts believe that HLVd has spread rapidly through infected clones. According to one plant research company’s chief scientific officer, cloning without testing for HLVd caused the viroid to spread between states and “all over the planet” such that “[a]nybody receiving any plants from the United States, especially from California, has the viroid in their grow.”
HLVd is also commonly transmitted through infected equipment (e.g., trimming tools) and by human touch from infected to non-infected plants. Additionally, the viroid likely spreads by direct contact between healthy and infected plants, through water and the soil around infected plants.
What Are States Doing to Slow the Spread?
To date, little action has been taken by the 39 states where medical and/or adult-use cannabis has been legalized. But some state agricultural departments have recognized HLVd’s prevalence in cannabis plants. In 2020, for example, California’s Department of Food and Agriculture (CDFA) released a Pest Rating Proposal for HLVd recognizing that the viroid could have a “negative impact on [cannabis] yield.” Beyond recommending “[s]trict sanitation” practices to limit the spread of HLVd, neither CDFA nor the California Bureau of Cannabis Control appear to have taken any concrete steps to address HLVd.
Change may be afoot, however, as states become more aware of HLVd’s prevalence. Vermont’s Cannabis Control Board (CCB), for example, issued a press release on June 8, 2023, notifying cultivators that HLVd had been detected in a cultivation site in the state. The CCB encouraged cultivators in Vermont to test for HLVd and adopt strict biosecurity measures to reduce the spread of HLVd, among other recommendations.
Testing for HLVd is often available through state-licensed commercial labs. Additionally, private companies sell commercially available sampling kits and rapid at-home tests that allow early testing. Because HLVd has only recently been discovered in U.S. cannabis plants and does not affect human health, states typically do not require state-licensed cannabis cultivators to test for HLVd presence. This may change, however, as states become aware of the potentially damaging economic effects of HLVd and work to prevent the further spread of the viroid in state legal markets.
What Should Cannabis Cultivators Do?
Inaction by state regulatory agencies and the federal government means that cannabis cultivators must limit the spread through testing and plant management protocols, breeding practices and legal safeguards.
Currently, there is no cure for cannabis plants infected by HLVd. Although several private companies have developed potential cleaning processes to eliminate the viroid in infected plants, the best defense against spreading HLVd within a facility remains rigorous sanitation measures and plant management.
In addition to rigorous sanitation measures, some cultivators have been working on breeding mechanisms to create either immunity (e.g., exposing plants with small amounts of the virus, much like a vaccine) or resistance (e.g., by observing and then propagating plants that do not become infected with HLVd). One such method is by conducting controlled crosses with plants that have been exposed to—but not become infected with—HLVd. Another method is to clone only healthy, virus-free mother plants. Cannabis farmers may also consider planting certain cannabis varieties that appear partially resistant to HLVd. Scientists recently discovered a cannabis variety, Jamaican Lion, in which the plant’s leaves and flowers turned purple as it fought the viroid and continued to test negative for HLVd, but the green leaves on the lower part of the plant (where scientists infected the plant) tested positive for the viroid.
Another mechanism cultivators can use to manage HLVd’s risk is implementing certain legal safeguards. For example, buyers and sellers of plant tissue culture, cuttings and plants should consider warranty and indemnification provisions related to the sale of plants that may contain—or be susceptible to—HLVd. To navigate contractual issues that may arise under various state contract laws, buyers should inspect any plants or plant materials within a reasonable time to ensure the plants are not infected with HLVd and reject any plants that may contain the viroid.
In addition to various contractual risk-allocation mechanisms, cultivators should consider whether they have (or can obtain) insurance to protect against losses from HLVd. Finally, companies required to make financial disclosures, securities filings (such as publicly-listed companies in the federally legal hemp industry) or taking outside investments should also consider whether they need to warn investors of the potential risks of HLVd.
Amy Rubenstein is a partner in Dentons’s Cannabis practice and a resident of the Chicago office. Throughout her two-decade career, Amy has crafted innovative legal solutions across highly regulated, ever-evolving industries (cannabis, chemical, pharmaceutical, insurance, manufacturing, and food & beverage). Margo Wilkinson Smith is a managing associate in Dentons’s National Health Care group and a resident of the Kansas City office. Margo’s diverse practice focuses on helping healthcare clients navigate federal and state regulatory issues.
Photo courtesy of Chris Wallis // Side Pocket Images.