Pesticide Use

Better research needs to be conducted about the potential health impacts of residual pesticides

A healthy cola grown without chemical pesticides.

Rampant pesticide use has consistently plagued the cannabis industry.

The problem can be traced to the fact that cannabis has been unregulated since the start of modern agriculture. Because the black market hasn’t had any oversight, common management practices have involved spraying whatever it takes to ensure a successful harvest.

The absence of official federal government rulings has left state regulators scrambling to establish, monitor and enforce these guidelines on their own. Unfortunately, this has created a lack of oversight and widespread misuse of unapproved pesticides. The Cannabis Safety Institute has reported “that pesticide residue on retail Cannabis products is often found at levels exceeding the allowable levels on any agricultural product.” The result is an ever-increasing need to understand how long pesticides persist on the plants and what classes of pesticides are considered safe for use.

Farmers using integrated pest management techniques can eliminate the need for toxic pesticides.

Denver, Portland organizations merge to form Cannabis Certification Council

By Brian Beckley

Denver’s Organic Cannabis Association and the Ethical Cannabis Alliance of Portland, Oregon merged in June to form the Cannabis Certification Council, aimed at creating high labor standards and rules for organic cannabis cultivation.

The new group will independently certify cannabis products as “organically grown and fairly produced.” Producers who meet the standards will receive seals to place on products for marketing purposes. According to a press release, the organization will serve as an independent nonprofit body that upholds “clear, achievable and robust standards.” Certification will be conducted by third-party experts to ensure integrity.

Due to federal illegality, cannabis producers are not eligible to receive “organic” certification from the USDA. Several private organizations have stepped into the void with standards that generally mirror those used by the government and have been certifying the practices and standards used at cannabis operations.

Dr. Bronner’s, makers of the top-selling organic and fair trade soap in the United States, has committed to provide seed funding and a matching grant to the organization. Founding board members include Les Szabo of Dr. Bronner’s, Laura Rivero of Oregon’s Yerba Buena, Amy Andrle of L’Eagle Services Denver, attorney Nick Richards of Vicente Sederberg and Dill Dill Carr Stonbraker & Hutchings and Ben Gelt of Par. Ashley Preece of the Ethical Cannabis Association will serve as executive director of the new organization.

“Our collaboration reflects the priority of the mission ingrained in both parties, and together we will immediately be greater than the sum of our parts,” Preece said.

While the new organization is based in Colorado and Oregon, Washington state also took a step toward creating standards for organic cannabis this spring with a new law that allows the state’s Liquor and Cannabis Board to develop and adopt regulations consistent with federal organic standards. The program will be voluntary and companies that meet the standards will be able to market themselves as compliant with the new standards, though still not legally allowed to use the word “organic.”

The Combustion Conundrum

Aside from tobacco, cannabis is the only agricultural commodity that is combusted, inhaled and absorbed through the lungs. This combustion and/or vaporization process is called pyrolysis. Pyrolysis is, by definition, a thermochemical decomposition of organic material at elevated temperatures, meaning the pesticide residue in the flowers or concentrates can actually change their chemical composition. And even if the chemical composition of pesticides is not changed, it can still travel with the smoke into the lungs, creating a unique challenge for regulators when comparing cannabis with tobacco and food commodities.

The inadequacy of extrapolating pesticide residue safety for cannabis and tobacco is rather significant. The Journal of Toxicology published a research article in 2013 titled “Determination of Pesticide Residues in Cannabis Smoke.” The article clearly explained that, “Since tobacco is not a food crop, the U.S. EPA has not set tolerances on the residue levels on tobacco crops. Consequently, tobacco is only monitored for compliance with U.S. EPA-approved pesticides while the residue levels are not federally regulated.”

Basically, the Environmental Protection Agency concluded that pyrolyzed pesticide residues in tobacco pose no short-term risk. Furthermore, since the cotton filters on cigarettes absorb a substantial percentage of the volatilized residues, concern for pesticide exposure to tobacco smokers has been minimal.

The Journal of Toxicology article also states that because cannabis smoking devices generally don’t have filters, “the potential quantities of pesticide residues that may be consumed increases dramatically when compared with tobacco smoking.”

In other words, regulations regarding pesticide residue cannot be satisfactorily translated to the cannabis.

The study concludes that: “The present study clearly demonstrates that chemical residues present on cannabis will directly transfer into the mainstream smoke and ultimately the end user. Recoveries occurred in the highest quantity with the hand-held glass pipe, ranging between 60.3% and 69.5%. Recovery from the unfiltered water pipe ranged between 42.2% and 59.9%, and recovery from the filtered water pipe ranged between 0.08% and 10.9%.”

This represents a serious concern for consumers and medical cannabis patients. From an entrepreneurial standpoint, this indicates excellent market potential for specialized filtration devices that reduce or eliminate pesticide residues for cannabis flowers and concentrates. However, is also bolsters the case for better regulatory oversight of pesticide use on cannabis.

Another problem is comparing cannabis to food. In this example, pesticide toxicities are quantified through oral ingestion. This is an appropriate measurement for cannabis-infused edible products, but it is not accurate for combusting or vaporizing flowers and concentrates. There is no better example of this than Eagle 20EW, a fungicide that contains myclobutanil as its active ingredient. When myclobutanil is heated, it decomposes into various gases, including hydrogen cyanide, an incredibly poisonous gas known for its use in the Nazi extermination camps of World War II. Needless to say, people should not be inhaling it — especially medical patients with compromised immune systems.

Healthy outdoor farms can lead to new inhabitants from nearby ecosystems.

The evolving landscape of regulated cannabis poses a dynamic challenge for state regulatory agencies. Trying to match pesticide use on cannabis with fruits and vegetables is of little value. Attempting to apply data from loosely regulated tobacco studies also appears inappropriate.

The Cannabis Horticultural Association (CHA), a trade group out of Humboldt County, California, is making a sweeping recommendation that combustion studies be conducted on all classes of pesticides approved by the state for cannabis. This is probably the single most important step to be taken for quantifying the health risks for consumers and medical patients. It will also help quantify appropriate analytical thresholds regarding pesticide and fungicide screening.

Cannabis represents a new class of agricultural commodity, and combustion studies to determine the health risks of pesticide residue have not been adequately performed. While neem, potassium salts, mineral oil, etc. may be safe and listed by the Organic Materials Review Institute (OMRI), there is no data on how they affect lung tissue upon inhalation.

This also applies to biopesticides. While biopesticides like spinosad, Grandevo, Bacillus thuringiensis (commonly known as Bt) and others may be safe and approved on food crops for oral ingestion, there is no data regarding the safety of inhaling these microbial-based controls. There is no data explaining whether these microbial pesticides are destroyed during combustion or even how long they can live after being sprayed on flowering plants. The pesticide and microbial screening standards are incomplete models until these types of combustion studies are performed and verified.

Generally speaking, it is safe to assume that most organic and biological pesticides sprayed during vegetative growth will be completely safe, but there is an unknown cutoff point to discontinue spraying during flowering. It’s that cutoff point that needs to be thoroughly tested and analyzed as well.

Pesticides can produce harmful fumes and requires workers to wear protective gear.

Systemic Problems

Another major concern is the systemic nature of certain pesticides.

Once again, myclobutanil shines a light into this dark underbelly of pesticide use. Myclobutanil is considered a systemic fungicide, meaning it is absorbed either through the roots or the leaf tissue and transported throughout the plant. It is hotly debated how long a systemic pesticide like myclobutanil can remain inside the cannabis leaf tissue, but conservative estimates suggest up to 12 weeks.

Farms and businesses that purchase clones from third-party growers have already experienced a jaw-dropping wake-up call. Clones sprayed with myclobutanil can actually have their flowers test positive for this chemical. What’s even more alarming is that some believe myclobutanil can remain in plants systemically after several generations. So when a mother plant is sprayed with myclobutanil, the clones taken off her would still contain residual levels of myclobutanil.

How many generations of plants can be affected by these lingering systemic pesticides? This is a question that is begging to be researched.

Alarms are also going off regarding the fact that systemic pesticides can remain in contaminated soil and compost.

“We have recently begun to see residual pesticide and fungicide toxicity in the soil of clients who have amended compost into their soils,” says Soilscape Solutions co-founder Samuel Deyton, a certified master soil consultant.

One common denominator seems to be the use of compost from facilities that accept waste from the viticulture (grape) industry as part of their compost production feedstocks. Further research has revealed that it is legal for the California viticulture industry to use pesticides and fungicides in their management programs that contain residuals that are banned in the production of cannabis.

“Of these substances, one in particular seems to stand out among the rest — myclobutanil — which is used as a fungal pathogen suppressant on vine grapes,” Deyton says. “Unfortunately, this substance is so resilient that even the thermophilic (high heat) composting process cannot affectively break down the carbon ring structure of the compound. Thus, feedstocks containing the toxins will contaminate the finished compost products. When compost containing these toxins is applied to soils in which cannabis is being cultivated, the cannabis plants accumulate these toxins in their plant tissue, as cannabis is both a dynamic and toxin accumulator. This can lead to failed pesticide and fungicide screenings of finished product bound for sale to consumers, and especially so for concentrates.

“We encourage farmers and producers alike to be extremely diligent in searching for clean compost and other organic matter materials to be used as soil-building inputs, and remind folks that even though that compost may carry an organic certification, that doesn’t always correlate to a clean product that is free of toxins that can result in failed screening at the end of the season,” Deyton concludes.

Growing from seed can remove the possibility of contaminated clones entering a cultivation facility.

Ecological Solutions

The landscape of cannabis horticulture has changed dramatically over the last decade. While myclobutanil is the villain of this article, there are plenty of other systemic pesticides such as imidacloprid, thiamethoxam and chlorpyrifos, just to name a few. There should be no reason whatsoever that a business should ever use toxic pesticides like abemectin, piperonyl butoxide, bifenazate and other chemicals you have no idea how to pronounce.

Ultimately, cultivating clean cannabis is about “being one” with your growing environment. Monitoring and controlling environmental conditions goes a long way in reducing the need to ever use pesticides. There are many businesses in the industry that can provide certifications, guidelines and strategies for growing pesticide-free cannabis.

Clean Green Certified founder and director Chris Van Hook says prevention is the best solution to pest problems. He suggests farmers grow from seed whenever possible and avoid bringing in third-party clones.

If clones are brought into the farm environment, they should all be quarantined and pre-treated. Use a 120x-160x microscope and thoroughly examine leaf surfaces. Keeping a clean environment is also paramount to success. Van Hook recommends that visitors and workers always wear clean clothing when entering the farm. The axiom “cleanliness is next to godliness” has never been truer.

Deyton recommends using approved essential oil sprays and other techniques such as “trap plants.” A trap plant is one that attracts agricultural pests, usually insects, away from nearby crops. Other methodologies suggest companion planting to attract beneficial insects that feed on pests. Using plenty of biologically active nutrients for your soil and compost teas will also boost your plants’ immune systems.

The CHA promotes the uses of integrated pest management (IPM) based on scientific research. IPM focuses on long-term prevention of pests and pest-related damage by managing the ecosystem. The IPM strategies from the CHA revolve around organic and biological methodologies. Following the IPM advice on cultural, mechanical, physical, biological and chemical controls, pesticide use can be reduced if not eliminated, especially when applying the proper biological controls like predatory mites.

Product Spotlight: Flower Girl Bud & Bloom Booster

Dry fertilizers are easy to use indoors and outdoors with a wide range of applications. They can be mixed into the soil before planting, scratched into the soil as a top dress for established plants or used in a fertilizer tea applied to the root system and as a foliar spray.

Dr. Earth’s Flower Girl Bud & Bloom Booster (3-9-4) is an OMRI Listed dry fertilizer made from carefully selected ingredients that plants need to thrive. It is also Non-GMO Project Verified and certified organic by the California Department of Food and Agriculture.

Flower Girl contains ocean-caught fishbone meal, valley-grown alfalfa meal, 6% humic acid from Leonardite, and cold-water kelp that naturally creates more abundant harvests. Additionally, it includes a blend of MycoApply certified beneficial microbes that bring the soil to life. This blend of organic nutrition and beneficials encourage multiple bud sites, maximum blooms and ensures that flowers are loaded with flavorful essential oils and resin. Flower Girl is designed to supply high levels of vital nutrition, improve overall soil texture, water retention and continually enhance the soil with each application.

Dr. Earth has also expanded its product line to include premium soil mixes, dry fertilizers, pest controls and liquid fertilizers.

Bulk sizing is available.

More information:

Currently, cannabis cannot be officially registered or called an organic product due to limitations from the federal government. But that in no way should stop someone from utilizing organic crop production methods. Ideally the CHA would like to see all farms reduce and eventually eliminate the use of pesticides based on customized, case-by-case strategies. A farm in Humboldt, for example, which typically used neem and potassium salts to control spider mites, completely eliminated pesticide use by introducing predatory mites at preset intervals, typically every few weeks.


Growers can use predatory mites like Neoseiulus californicus to feed on juvenile spider mites and their eggs.

The Evolution of Pesticide Use

As states like California enter the foray and raise analytical standards, it will become increasingly important for businesses to cultivate cannabis that passes pesticide and microbiological screening. Testing labs in Washington and California that have received ISO 17025 accreditation, an international standard for technical competency, signify that the industry and regulations are becoming more regimented and stringent.

Pesticide manufacturing companies are now making the push to have cannabis listed as a crop on the label. General Hydroponics has filed for approval with the EPA for special local need labeling for four products in states that have legalized recreational cannabis. If approved, Prevaysn (capsicum, garlic, soybean oil), Defguard (bacillus amyloliquefaciens), Exile (potassium salts) and Azamax (neem extract) would become the first registered pesticides that specifically list cannabis on the label. The ingredients used in these four products typically fall under the organic and biological controls platform and therefore could set a precedent as appropriate pest control products in the industry.

Using the right management practices can mean the difference between your product being approved or destroyed. Pesticide management starts with a clean environment and ends with clean testing. Proper pesticide management can also put businesses one step ahead of greedy commercial competitors who will increasingly have their products destroyed from failed testing.

Feeling good about providing an authentically uncontaminated product is a noble path that takes discipline and commitment. Many people believe there will be a big opportunity for those who can provide equipment, information and consultation for cultivating clean, pesticide-free cannabis.


Russell Pace is the president of the Cannabis Horticultural Association (, a trade group promoting sustainable management practices for cannabis. The CHA maintains an online horticultural resource center and conducts experiments, product reviews and disseminates the information through its publications and electronic media. Its mission is to conduct, promote and build all branches of this horticultural science.




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