As cannabis in California finds its place at the forefront of the legislative arena, states are publishing resource materials to provide governing transparency and assurance to state and local constituents. These guidelines establish government contacts on the local and state level to assist growers and businesses with making the transition into a new political and regulatory environment.
A pesticide is a substance used to prevent, destroy or repel an organism. This category can include substances such as herbicides, insecticides, and fungicides. Pesticides are considered an integral and important player in the agriculture business, but are definitely a highly regulated practice when it comes to crops that are destined for human consumption.
The California Department of Pesticide Regulation’s number one priority is to protect the human health and the health of the environment. Its regulation of the sales and use of pesticides in the state is an effort to foster pest management practices that reduce the levels of risk to growers, consumers, and the environment as much as possible.
The Department of Pesticide Regulation’s published California Guidelines describe the current legal pest management practices for marijuana growers in the state.
California’s List of Accepted Active Pesticidal Ingredients
The Guidelines’ published list (see Table 1) of acceptable pesticides to be used on cannabis in California includes pesticides which have been found to be safe by the federal Environmental Protection Agency (EPA), and are thusly exempted from residue tolerance requirements. Residue tolerance requirements are set by the U.S. EPA for each pesticide used on food crops. They dictate the amount of pesticide residue that is allowed to remain in or on each treated crop with “Reasonable certainty of no harm.”
Because the active ingredients in California’s published list have been deemed safe, they are exempted from these requirements and can be used without fear of dangerous contamination. Some of the pesticides listed in California’s Guidelines are bacterial-based insect pathogens. These are a new type of pesticide that are environmentally friendly pest control tools that can be easily integrated into a pest management program. These insecticide bacterial and fungal agents interact with pests in a variety of mechanisms that eventually overcome the pest’s immune responses to infect and eradicate it.
Other pesticides on the California Guidelines are classified as biofungicides. Biofungicides are living microorganisms that are active in root, soil, and leave systems, and have the ability to control fungal or bacterial pest threats.
All the active ingredients published in California’s list of acceptable Active Ingredients for use on cannabis in California are either exempt from registration with the EPA or have been registered with broad enough permits to include cannabis application. These registration requirements refer to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) law which specifies that pesticides distributed or sold in the United States must be registered and licensed by the EPA. Substances which are registered as pesticides under FIFRA must not “generally cause unreasonable adverse effects on the environment.”
The EPA includes a list of substances which do not need to be licensed by FIFRA; these include human drugs, animal drugs, vitamin hormones, and products intended to aid the growth of desirable plants. In the California Guidelines’ list, the active ingredients which are exempt from these registration requirements are essential oils such as peppermint oil or rosemary oil, substances commonly used in the food industry. These essential oils are similar to those extracted from from terpenes that are of extremely low to no toxicity in humans. The remaining pesticides have been registered under FIFRA, as required, and have been licensed for use that is broad enough to include use on cannabis in California.
Common Pests Affecting Cannabis in California
The state publishes its guide of common pests and their modes of infestation and attack as the governing agencies’ understanding and observations change with weather and climate patterns every few years. There are different classifications for known cannabis pests that are a threat to indoor plants versus outdoor plants, as well as the portions of the plant and harvest which they attack. In recent years, the pests which have drawn the most attention are noted on the state’s Guidelines. It is likely that the pests from recent years pose a more daunting threat because they are species which have adapted and survived despite the state’s drought years. Many of the pest species mentioned in the Guidelines have cyclical population crests and falls, meaning their threat is based on a periodicity while other pest families are mainstays of general greenhouse cultivation and are constant considerations.
The pests that can target cannabis in California include various categories: mites and insects, mammals, and diseases. (The state has announced that it will soon add weeds to this list.) California provides recommendations for pest management practices for marijuana grown indoors and outdoors. These practices go beyond what pesticides cultivators should use — the recommendations include physical pest management practices such as sticky traps, strategic hosing and flooding, careful pruning, and other plants which may prove useful in protecting the cannabis. The appropriate pesticide recommendation is to be used as an adjuvant method.
The mammalian considerations for pest management of cannabis in California are interesting because they do not only include small mammals such as rodent species, but also much larger species such as deer and black bears. While the smaller mice and rat species pose a threat to the integrity of leaves, seeds, and roots, the larger species are mostly an annoyance because of their tendency to knock over plants while they forage.
California’s Growing Knowledge of Cannabis Pests
There are varying degrees of pests and their importance in pest management. There are definitely pests which must be dealt with immediately, while others do not require a comprehensive defense strategy except to keep an eye on collective damage which may affect the overall health of the plant.
There are still a number of pests which have not yet been officially identified in California. There are several cannabis pests that are known in other states which have not yet become a part of the Californian compendium of pest management. As more marijuana is planted throughout the state, California’s entomologists will be able to collect and identify new species of potential pests.
Cranshaw, Whitney. 2013. Challenges and opportunities for pest management of medical marijuana in Colorado. PResentation.
McPartland, JM. 1996. Cannabis pests. J. International Hemp ASsociation. 3(2): 49, 52-55.
Pickett, CH & RL Buggs, eds. 1998. Enhancing Biological Control: Habitat management to promote natural enemies of agricultural pests UC Press, Oakland, California.
Source: THC Design