In this Growers Spotlight, we discuss pesticide use as it is applied in Washington and the problems that commercial and hobbyist growers face with regards to pesticides.To skip to any section within this article, click the links below:
What are Pesticides?
Pesticides are defined as chemical or biological preparations that are designed to control, repel, and/or mitigate a pest. Pests can include:
Pesticides can come in many varieties and are usually defined by the type of pest they control and their mechanism of action. For more details, click the accordion below.
Pesticide Details
- Biological or Chemical
- Some pesticides are considered biopesticides because they incorporate elements from living organisms or are living organisms themselves. These can include naturally occurring substances like the essential oils, microorganisms that control pest populations, and/or genetic substances that have been introduced into a plant’s genome to protect it.
- Chemical pesticides are generally synthetic (manmade) or are a chemical derivative of a naturally occurring product.
- Mechanism of Action
- Some pesticides work by interfering with the nervous system of an animal pest.
- Some pesticides work by disrupting enzymes essential to the metabolism of a plant or animal.
- Some pesticides work due to their toxicity to certain organisms.
- Some have unique mechanisms by altering the life cycle of the target organisms. This can include defoliants, desiccants, insect growth regulators (IGRs), and plant growth regulators (PGRs). IGRs and PGRs use hormones to control their targets.
- Biodegradable or not
- Relatively self-explanatory, but some pesticides can persist in the environment for long periods of time (like DDT), whereas others can degrade.
- Type of Pest they Control
- Most pesticides are specific to a certain class of pest. These can include mites, algae, various microorganisms, nematodes, mollusks, rodents, insects, mollusks, weeds, fungi, and more.
- Most have -cide as a suffix in their name, which means “to kill.” Fungicides, for example, are meant to “kill” or otherwise control fungus. Rodenticides kill rodents, miticides kill mites, etc.
Washington State Department of Agriculture (WSDA)

What are your goals with your fertilizer and pesticide program?
How does the WSDA differ from other states' departments of agriculture?
Is there any particular area or group of areas that you feel the WSDA really excels?
How does the registration process for pesticides work in Washington?
How does the registration process for fertilizers work in Washington?
What would qualify as a minimal risk pesticide?
What penalties do companies face for failure to comply?
How does teaming up with the Washington State Liquor and Cannabis board change things?
Cannabis and Pesticides
It really isn’t a lot different than growing tomatoes, other than the Feds might have a slight problem with it.— Erik Johansen
What are the most commons pests for cannabis in Washington, and how do you handle them?
Pests we hear about the most are mites, spider mites, broad mites, powdery mildew, mold, thrips, and aphids. The pests you’d have on greenhouse crops will also prey on cannabis. We don’t make recommendations for any pesticide over another. When we register products, we provide that information to WSU because they’re our state land grant. They make that information available on a public database (PICOL) and for the cannabis growers. Since there very few pesticides that are specifically labeled for use on cannabis, we have developed a list so they have guidance on what’s allowed for use on cannabis. That relates back to both the rules from the Liquor and Cannabis board which is the state lead agency for cannabis regulation. The Department of Health is involved in regulation of what they term “compliant” products, which most people refer to as medical marijuana (MMJ). Our list is used by both those agencies and we’re also in the process of working out a process of doing the same thing for hemp for the Department of Agriculture. Editor’s Note: Washington defines the cutoff between cannabis and hemp as being 0.3% THC, with hemp having less than that amount present.
What differences do you see in pesticide use between commercial cannabis growers and big agricultural growers?
Many growers are interested in getting into Integrated Pest Management (IPM). What advice would you have for them?
If you’re not practicing IPM, and you’re trying to grow cannabis, the odds of failure are 100% or something close to it.— Erik Johansen
Given the tools available to cannabis growers, IPM is essential. There’s some consultants that help some of the cannabis growers here with IPM. If you’re not practicing sanitation, if you’re not checking the plants coming in, if you’re not working with beneficials and if you’re not using pesticides correctly at the right time, good luck. You really should be monitoring or working with somebody who’s helping you monitor what’s going on at your grow. Monitor, monitor, monitor. Unfortunately some of the pests that the cannabis growers are dealing with are tiny little mites. You need a high-powered lens to see the stupid things. A variety of companies have predatory mites, which I think could be incredibly useful. There aren’t great miticides for growers to work with, so having predatory mites that you’re releasing periodically can keep the number of mites under control. Related Article: If you’re interested, click here to read more about Integrated Pest Management from a grower’s perspective.
What should cannabis growers be looking out for when purchasing pesticides or fertilizers?
Where do you see the cannabis industry heading in regards to pesticide use?
What would you like to hear from commercial cannabis growers?
Do you have any numbers for growers to call in if they need assistance in Washington?
Did you want to give any shout outs?
Growers Network Member Questions
We need to treat this as a real business, a real crop, and act like adults.— Erik Johansen
What is your opinion on "clove and rosemary extract" types of products that are continually hitting the market? How can a grower ensure they are compliant when using products such as this?
Can you differentiate between a "pesticide," a "crop improvement aide/soil amendment," a "fertilizer," and a "foliar spray/leaf shine?" What are the regulations pertaining to each for cannabis production?
What are your opinions on Plant Growth Regulators (PGRs) and Plant Health Regulators (PHRs)? What are the laws in Washington concerning their use?
Do you feel the Washington State pesticide program would make a good template for other states to follow for pesticides/allowed products in cannabis production?
Resources
- Want to learn more about WSDA pesticide regulations? Check out their page on pesticides and marijuana!
- Want to learn about pesticides safety regulations for workers? The WSDA recently released a helpful PDF about safety.
- Looking to learn about chemigation or fertigation? The WSDA has put out a helpful guide about fertigation.
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