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IPM - Chemical Controls for Indoor Cannabis Production

December 08, 2020

  • What Are Chemical Controls?
  • Types of Pesticides
  • Potential Environmental Effects
  • Preventive & Curative
  • Mode of Action

What Are Chemical Controls?

Integrated Pest Management (IPM) is a multifaceted approach to control pests and pathogens affecting plants in an ecologically safe manner. Chemical controls consist of the use of pesticides which is one of several tactics used in a successful IPM strategy. Under the Federal Insecticide, Fungicide Rodenticide Act (FIFRA), pesticides are defined as any substance or mixture that’s used to prevent, repel, mitigate, or destroy any pest. In the state of Colorado, pesticides used in either residential or commercial settings are placed on an approval list by the Colorado Department of Agriculture (CDOA). In general, most pesticides that are OMRI listed or have a 25(b) exemption from EPA registration are safe for use on indoor cannabis plants. Pesticides have been given a negative connotation due to more toxic pesticides being used excessively outdoors by large agricultural businesses and by commercial cannabis cultivators prior to pesticide testing being required, but there are numerous pesticides that are far less toxic and safe for the environment that can be utilized in a curative and preventive manner. It is important to consider using chemical controls as part of a larger program that is implemented to limit the impact of pests and pathogens that target cannabis plants indoors. Additional IPM controls that should be used in tandem with chemical controls include, but are not limited to: cultural controls, environmental controls, physical controls, and mechanical controls.

Types of Pesticides

Pesticides are divided into categories that range in level of toxicity. In general, common pesticides are classified as fungicides, herbicides, and insecticides. Fungicides are the least toxic to humans and insecticides are the most toxic of pesticides to humans. Each type of pesticide has sub-categories that also range in levels of toxicity. For example, the sub-categories for insecticides include: soaps, microbial products, insect growth regulators, botanicals pyrethrins, chlorinated hydrocarbons, carbamates, and organophosphates. These insecticide categories are listed from least to most toxic. OMRI Listed pesticides are pesticides listed for use in organic production and processing. OMRI stands for Organic Materials Review Institute which is an international nonprofit organization. OMRI listed products are allowed for use in certified organic production according to the USDA. Pesticides that have a 25(b) exemption from EPA registration are chemical products that contain active and inert ingredients considered minimum risk under Section 25(b) of the FIFRA (Federal Insecticide, Fungicide Rodenticide Act). These pesticides are not required to have an EPA registration number and they are not screened for efficacy or toxicity. This exemption from Federal registration is only permitted if the manufacturer only uses approved active and inert ingredients. There are 31 approved active ingredients and nearly all of them are natural products.

Potential Environmental Effects

There are potential negative environmental effects by using pesticides indoors, depending on what pesticides are being used and how they are being used and disposed of. In the United States, homeowners and agricultural businesses use over a billion pounds of pesticide active ingredients annually. Some pesticides are water-soluble and can leach into groundwater or end up in various bodies of water such as streams, lakes, and rivers depending on conditions. Other pesticides can persist in the environment for long periods of time, others can biomagnify across the food chain and become more toxic to predators. In general, the potential effects of most pesticides are not measured or tested, but if you use pesticides that are OMRI listed or that have a 25(b) exemption from FIFRA, then you will know that these pesticides are generally safe for the environment if used according to product labels.

Preventive & Curative

Pesticides that are OMRI-listed or have a 25(b) exemption should be used in combination with other approaches for more effective, long-term control of pests and pathogens. These pesticides are selected from the Colorado Department of Agriculture’s Pesticides For Use In Cannabis Production list in an effort to minimize any potential harm to people, nontarget organisms, and the environment. Selecting pesticides that are safe for the environment and most effective for control can prevent any short-term or long-term harm to local water quality when used in indoor cannabis production. Preventative doses of pesticides are lower usage rates meant to be used as part of a regular schedule and to be cycled with other pesticides. Curative doses of pesticides include higher usage rates that are meant to be used when a pest or pathogen outbreak occurs to reduce pest populations to an economically safe level.

Mode of Action

The toxicity of a pesticide can be related to the mode of action or how it affects a pest. For example, insecticidal soaps’ mode of action is to interfere with the function of an insect’s waxy outer covering or cuticle. This will have little to no effect on mammals. Insecticides have four different modes of action and depending on what pest you are managing, the mode of action is important to mitigate pests. The four modes of action for insecticides are stomach poison, contact poison, systemic poison, and fumigant. Stomach poison means that the insecticide must be ingested by the insects in order to be effective. Contact poison means that the insecticide must make contact with insects to be effective. Systemic poison means that the insecticide is absorbed by plants, then it gets into insects through the ingestion of the plant. Fumigant means that the insecticide must be absorbed as vapors across insect membranes. Each mode of action has its own advantages and disadvantages and may serve better to combat one pest or another or even different life stages of pests. Looking at the example of insecticidal soaps, a contact poison will kill individual spider mites affecting cannabis plants, but they will continue to come back as it has a short half-life and it has to penetrate a soft-bodied insect’s body covering and disrupt cell membranes which causes the contents of cells to leak out resulting in death. Systemics are generally avoided on plants for consumption because of their long half-life and fumigants are typically not used in commercial cannabis production due to the high toxicity to mammals.


  1. Hoffmann, M.P. and Frodsham, A.C. (1993). “Integrated Pest Management Control Tactics”. Biological Control. Cornell University College of Agriculture and Life Sciences.

  2. (n.d.). “Section 25(b) Chemicals”. University of Nebraska. Institute of Agriculture and Natural Resources.

  3. (2011). “IPM Tactic Chemical Control”. PennState Extension. Pennsylvania State University College of Agricultural Sciences.

  4. (n.d.). “Frequently Asked Questions”. IPM Institute of North America.

  5. (2001). “Potassium Salts of Fatty Acids General Fact Sheet”. National Pesticide Information Center. Oregon State University.

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