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Potassium Salts of Fatty Acids Rundown

April 19, 2019

  • Derived From
  • Laws Regarding Use
  • Mode of Action
  • Persistence in Environment

Derived From

Potassium salts of fatty acids can be a valuable tool to manage pests on variety of plants and fruits. They have been around for some time now, “Potassium salts of fatty acids are commonly referred to as soap salts. They are used as insecticides, herbicides, fungicides, and algaecides. The first pesticide product containing soap salts was registered for use in 1947” (Oregon, 2001). Besides soap salts and potassium salts of fatty acids, another common name for them is insecticidal soaps. An individual could use insecticidal soaps to target a larger variety of soft-bodied pests without adversely affecting their health and the environment (Pundt, 2015). Insecticidal soaps are produced by combining potassium hydroxide and fatty acids found in many different plant oils. These fatty acids can be pulled from coconut, olive, and castor plants (Valles, 2019). This is generally how many dishwashing soaps and detergents are made, but because they are designed to remove grease they can cause plant damage to the plant leaf surfaces. This is why it is important to take additional caution when attempting to use such products that are not labeled as a pesticide on cannabis plants.

Laws Regarding Use

According to the EPA, the residues from the use of this active ingredient does not require a food tolerance which means it is relatively safe to eat. However, the Colorado Department of Agriculture (CDOA) and the federal government has not established any pesticide residue tolerances for cannabis. It is also important to note that the CDOA does not recommend the use of any pesticide not specifically tested, labeled and assigned a tolerance for use on cannabis because of the potential negative effects that can occur. There are however, several pesticides in which they can be legally used on cannabis in the state of Colorado after registration with the CDOA because certain active ingredients of a pesticide product are exempt from requirements of a tolerance. (Colorado, 2019). There are two popular insecticidal soap pesticides that are approved for use in personal grows and commercial grows in the state of Colorado:

  • M-Pede
  • Des-X

Mode of Action

Many individuals know that pesticides kill pests, but less individuals know how pesticide chemicals react with pests. How a pesticide works is known as the mode of action. Insecticidal soaps are effective on soft-bodied pests by contact. When the pest is directly sprayed, the fatty acids penetrate their body and cause the contents of their cells to leak out causing them to die. There is minimal residual pesticide activity once the spray application has dried as it rapidly degrades (Kistner, 2014). Adult pests with a stronger outer covering may be less affected by insecticidal soaps as well as pest eggs which is why soft-bodied pests and larvae are the primary targets. When dealing with any particular pest it is important to understand the biology and life cycle of the targeted pest for more effective management. The most common soft-bodied target pests include: aphids, leafhoppers, thrips, whiteflies, and spider mites. Any of these pests make acceptable targets for insecticidal soap applications. If an insect has not been coated with the spray, it will not be affected by walking over or ingesting plant material that has been treated with soap. It is imperative that the pesticide makes direct contact with the target pests in order to be effective as well as making contact with the undersides of leaves where a lot of pests sleep and reproduce. Spraying only the upper sides of leaves will be ineffective in treating the target pests.

Insecticidal soaps should make direct contact with target pests to be effective.

Another factor to consider is plant sensitivity which can be influenced by a number of factors. Some of these factors include pest pressure, cannabis strain or cultivar, environmental conditions, mixture concentration and pH, frequency of applications, and overall plant vigor (Pundt, 2015). Potassium salts of fatty acids can be mildly toxic to cannabis plants if used incorrectly. When cannabis plants are in the flowering phase they develop trichomes and pistils which hold the soap on the plant surfaces longer which could potentially result in a burn if not used correctly. The mild toxicity is the burning of leaves and flowers such as yellow or brown spotting. In order to avoid any possible damage through spray application, cannabis plants in late flower as well as young transplants and clones should be avoided to prevent any damage.

Persistence in Environment

Potassium salts of fatty acids have a soil half-life under 24 hours. They are biodegradable and do not persist in the environment. Potassium salts are mildly toxic to birds, mammals, and fish. In mammals, the insecticidal soap can be mildly irritating to the skin and eyes when contact is made. They are highly toxic to aquatic invertebrates though. Which is why it is important that insecticidal soaps do not contaminate water either through direct application, cleaning pesticide application equipment, or by the disposal of rinsate containing potassium salts of fatty acids. Many insecticidal soap products can be used on various food crops up to the day of harvest and for cannabis it is possible to use until the late flower stage of a plant’s life cycle.


It is possible despite all of your best intentions towards good cultural practices to fail to prevent pests from appearing. When this occurs, chemical controls such as potassium salts of fatty acids can be used with effectiveness in your cannabis garden. Take your time to apply the pesticide correctly, understand your target pest, and understand the environment that the plants are grown in to maximize the efficacy of potassium salts of fatty acids.


  1. Oregon State University (2001). “Potassium Salts of Fatty Acids”. Oregon State University. Retrieved from http://npic.orst.edu/factsheets/psfagen.pdf&ved=2ahUKEwjS-Kfqq8jgAhVSOq0KHYz8AQgQFjABegQIDhAH&usg=AOvVaw1SRWMCHoqb79soBjL0bBf-.

  2. Kistner, Brett M. (2014). “Sodium or Potassium Salts of Fatty Acids”. University of Minnesota. Retrieved from https://sites.google.com/a/umn.edu/phar6157s13/home/sodium-or-potassium-salts-of-fatty-acids.
  3. Pundt, Leanne (2015). “Insecticidal Soaps”. UConn Home & Garden Education Center. Integrated Pest Management Program Department of Plant Science and Landscape Architecture UConn Extension. Retrieved from http://www.ladybug.uconn.edu/FactSheets/insecticidal-soaps.php.

  4. “Pesticide Use in Cannabis Production Information” (2019). Colorado Department of Agriculture. Retrieved from https://www.colorado.gov/pacific/agplants/pesticide-use-cannabis-production-information.

  5. Valles, Steven M., Koehler, Philip G. (2019). “Insecticides Used in the Urban Environment: Mode of Action”. University of Florida - School IPM. Retrieved from http://schoolipm.ifas.ufl.edu/newtechp13.htm.

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