Testing Medical Marijuana for Pesticides

By Jodi McDonald
Published: April 1, 2017 | Last updated: April 20, 2022 10:50:50
Key Takeaways

With the cannabis industry still in its infancy when it comes to government standards, allowable pesticides are emerging as a source of concern for human health. Jodi McDonald explains why more scrutiny is needed to protect cannabis users from harmful chemicals.

Pesticides might be something that you are thinking about a lot recently as they have been in the news and have played an important role in cannabis product recalls in Canada.


What do we know about pesticides? In general, pesticide use is a calculation to increase yield by reducing loss to pests. Pesticides are approved for use through a rigorous program that considers the health and safety of the consumer and the individual applying the product to a crop, as well as the environmental impact.

Many pesticides are considered based on their use in food crops, which is a key point in the cannabis industry as cannabis is not consumed in the same way that lettuce or tomatoes are. Due to the young age of the industry in a legal sense, we are only beginning to collect meaningful data about the risks and concerns of control products utilized during production.


In Canada, Health Canada has published a list of 13 approved pesticide products for cannabis producers as of February 1, 2017. A look through this list reveals that there are a very limited number of chemical products that cannabis growers have at their disposal when a pest problem shows up. Most of the approved products are biological control products. Compared to the products that are available for growers in the US, this may seem like Canadian growers are at a great disadvantage.

grower spraying cannabis with pesticide


Chemical pesticides have benefits as they act quickly and can reduce or completely eliminate an invading pest. Unfortunately for Canadian producers, these are not approved for use in cannabis crops.”


In Colorado, the Colorado Department of Agriculture has also compiled a list of approved products for pest control as of March 6, 2017. Compared to the list available for Canadian use, this list is 27 pages long, so offers a wide variety of choices for growers.

Biological pesticides work because the insect or organism in the product is a natural predator or parasite to the pest problem. These products are effective because once they have done their job and rid a crop of the unwanted pests, they die from starvation. Biological pesticides require an awareness of the health of a crop and diligent application of the products; this can mean frequent reapplication to completely eradicate a problem.

Chemical pesticides have benefits as they act quickly and can reduce or completely eliminate an invading pest. Unfortunately for Canadian producers, these are not approved for use in cannabis crops.

Recently, the pesticide Myclobutanil has been in the news related to cannabis recalls in Canada. Myclobutanil is a common chemical used to eliminate powdery mildew on plants. It is interesting to know that this is acceptable for use on edible crops, but not approved for use in tobacco in the United States and Canada, as well as not being approved for use in cannabis in Canada.

Myclobutanil is a good example of pest control and science not being applied in equal measure. This pesticide works by blocking an enzyme in fungal cells; this impacts the way the fungal cell membrane is built and maintained leading to cell death. It is a systemic pesticide which means that it enters the plant through the leaves and then spreads internally through the plant to provide protection to the whole plant and not just at the site of application.

Since this pesticide is carried inside the plant, it cannot be washed off. While it decreases over time, the frequency that it has been applied to the crop will impact the final amount left in the plant at harvest.

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Also concerning is that the pesticide is soluble in common solvents used in production of cannabis oil, which means as the cannabis oil is being concentrated the pesticide is being concentrated too.

At temperatures above 205°C, the pesticide breaks down into a number of byproducts, one of which is hydrogen cyanide. This byproduct is dangerous because it is known to cause problems in most of the major systems in the body—the brain, the lungs, heart, and hormone control center.

Overall, Myclobutanil is a terrible choice for pest control in cannabis. While it is effective against powdery mildew, it has a high cost of use for the patients who are exposed to products treated with it. This is one clear example of a common pesticide used in one industry being adopted by a different industry without consideration given to the way the crop is processed or consumed.

In response to the recent product recalls, Health Canada has committed to random testing of products for pesticides to provide a level of assurance to the patients in Canada.

For personal growers, the use of pesticide products is not regulated by the federal government, so the bottom line is to be diligent, know what you are applying to your plants and what the potential impact is to you as a grower and you as a patient.

You can’t see pesticides or the residues, but a good test lab will have sensitive equipment that will detect the presence of pesticides.


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Written by Jodi McDonald

Profile Picture of Jodi McDonald

Jodi McDonald is the president and founder of Keystone Labs and is a medical microbiologist, inventor and super science-geek. She has 20 years’ experience in the quality control, regulatory, and quality assurance environment for the pharmaceutical industry. Jodi believes testing is essential for taking control of your personal health.

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