A Primer on Pesticide Use in Hemp

Columns - From The Field

A rundown on which pesticides are approved for hemp and how these inputs gain approval for use on the crop

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January 19, 2022

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The pesticides available for hemp use have changed significantly over the past several years in the U.S. In 2019, there were no registered products through the Environmental Protection Agency (EPA); there are now 59.

When no EPA-registered products for hemp use existed, some states took matters into their own hands. For example, various state departments of agriculture published lists of pesticide products for both hemp and state-legal cannabis. Some pesticide products are exempt from EPA residue testing, so while hemp may not explicitly be on the label, states like California, Colorado, Oregon, and Washington made lists specific for cannabis that included exempt products or products that have broad label language about crop usage.

While this provided some chemical control options in certain states, it also caused confusion. As growers and businesses seek out new opportunities, they may be unaware of the complexities that involve using pesticides on hemp and applying for approval on new pesticides for use on hemp.

But before we dive into the complexities, let’s start with the basics.

Classifying Pesticides

With many people from different backgrounds entering the hemp and cannabis space, there can be confusion about production and pesticides—namely, what is considered a pesticide.

The Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) defines a pesticide as “(1) any substance or mixture of substances intended for preventing, destroying, repelling, or mitigating any pest, (2) any substance or mixture of substances intended for use as a plant regulator [such as plant growth regulators], defoliant, or desiccant, and (3) any nitrogen stabilizer.”

“Pest” is a broad term that can include nuisance pests or economically important pests. Economically important pests—which include rodents, weeds, pathogens, insects, and nematodes—can cause loss of crop yield by either directly damaging the marketable portion of the plant or indirectly by affecting the productivity of the plant.

Pesticides are made of both active ingredients and inert ingredients (anything added along with the active ingredient in a pesticide, such as emulsifiers, solvents, fragrances or dyes). Pesticides get placed into three categories: conventional, antimicrobial, and biopesticides. Conventional products typically contain synthetic active ingredients. Antimicrobial products are used on inert (non-living) objects like equipment to sanitize and disinfest to reduce the spread of pests. Biopesticides have active ingredients derived from natural or biological sources. Most products available to hemp growers are biopesticides.

Many people may wonder why we don’t see a lot of conventional pesticides registered for hemp use. There are several reasons for this. Adding a new crop to a pesticide label is expensive and takes time. Trials also need to be run on that crop, pesticide residues must be measured, and the overall efficacy and safety need to be evaluated. With hemp still making up a small amount of acreage compared to other crops in the U.S., large companies may not be able to justify the expense and time it would take to get hemp added to a conventional pesticide label. Hemp also has many different applications, as well as various processing and consumption options, so it requires studies on how pesticide residues change during processing.

Current Registered Pesticides

The process of getting hemp on a pesticide label typically requires companies to go through an EPA label amendment application, which includes submitting supporting data for the active ingredient and all necessary administrative paperwork. (States then have their own pesticide registration process, which isn’t as rigorous as the EPA’s.)

The EPA has officially registered 58 biopesticides and one conventional pesticide for use on hemp, most of which are for insects, mites, and pathogens. (See a full list here.) Many of these products are commonly used in organically grown crops and have low residual activity (meaning they break down quickly in the environment and are often sensitive to UV or wash away easily in the rain); this can mean growers need to apply the products more frequently, as they are not as persistent.

Some of the most popular pesticides for use in hemp contain neem oil, or the active ingredient Azadirachtin, to manage certain insects, mites, and pathogens. In fact, neem-based products, which are derived from neem tree seeds (Azadirachta indica), dominate the approved pesticides list. 

Hemp displaying a phytotoxic response to a pesticide

Insecticidal soaps are another popular product among cannabis growers. These soaps work well on soft-bodied insects and mites—such as thrips and aphids—and are most commonly used in controlled or semi-controlled environment production.

Additionally, products that contain viruses, bacteria, and fungi are also popular among growers. These products tend to be very specific on which pests they target, which is essential, since growers want to avoid damaging beneficial organisms on or around the plant. The key with pesticide use is to apply before you experience a serious outbreak, especially if you are using products that are not very strong. If there is a serious pest outbreak or if the plant’s weeds are very tall, the products won’t be as effective, as the damage may have already been done.

Pesticides have labels and safety sheets that specify what protective equipment to wear, how to store and apply the products, and their intended uses. It’s important to understand product labels so you don’t damage your crops.

Pesticide Registration

Pesticide use becomes more complicated with the additional classifications of products based on their ingredients, some of which do not require hemp use to be on the label. FIFRA is the statute that governs the registration, distribution, sale, and use of pesticides in the U.S., while the EPA is the governing body that registers products following FIFRA.

FIFRA, however, contains exemptions that allow companies to bypass EPA registration. For example, 25(b) pesticides are classified as products that pose a minimum risk and are therefore exempt from FIFRA registration. They don't need to contain "hemp" on the label for producers to use them.

Certain criteria must be met for this exemption—primarily, both active and inert ingredients must be on the EPA’s “Active Ingredients Eligible for Minimum Risk Pesticide Products” list, and the “Inert Ingredients Eligible for FIFRA 25(b) Pesticide Products" list.

While minimum-risk pesticides do not need to go through FIFRA registration, many states require state registration for these products. When in doubt, call your state pesticide office to get clarification on products and their use.

Also, minimum risk does not mean no risk. When using any pesticide product, growers should follow the necessary precautions to prevent injury to themselves, others, and the plants. Many minimum-risk products contain plant essential oils, for example, which can be an irritant for some people and animals. I generally don’t recommend 25(b) products for hemp because there is limited efficacy data, and products containing essential oils can burn the plants and are expensive.

Branching Out

There are other options for pesticide use on hemp outside of waiting for the EPA to register products, but these options still take time and effort.

Pesticide registrations under FIFRA section 24(c) are used for a “special local need” within one state or several states. This registration method requires evidence from the state pesticide office that there is a pressing need to use a specific pesticide on a crop that is not listed on the current product label. It also requires support from university specialists and the product manufacturer for the best shot at EPA approval.

There is also emergency-use registration under section 18 of FIFRA, which allows for the use of pesticides without residue data to address emergency conditions, but this is often only for a brief period of time (typically a year).

Many producers and consumers are generally not interested in heavily sprayed hemp and cannabis, though. In addition, Canada has set limits of quantitation for certain pesticides in cannabis. While the EPA has not done this in the U.S. for hemp, many states have their own pesticide residue testing requirements for cannabis and hemp products.

As production increases, so will the demand for pesticides, which could lead to larger companies registering conventional products. We may also see a shift in the types of products available if hemp production for grain and fiber increases. Until then, it is critical that growers utilize integrated pest management along with the appropriate use of approved pesticides in their hemp.