Environmental Protection Agency’s Cancellation of Chlorpyrifos Tolerances: Alternatives for Management of Key Crop Pests

By Robert Koch and Theresa Cira et.al

In a pre-publication of a final rule released on August 18, 2020, the EPA announced  that the agency is revoking all tolerances for chlorpyrifos. A “tolerance” represents the maximum level of pesticide residue legally allowed in or on raw agricultural commodities and processed foods. Revoking of tolerances will stop the use of chlorpyrifos on all food and feed, taking effect six months after the final rule is published. See 40 CFR Part 180 for a list of chlorpyrifos tolerances on food commodities. The pre-publication announcement from EPA indicates that growers can still use chlorpyrifos through the end of the 2021 growing season.  Non-agricultural uses are unaffected by the final tolerance rule. 

Background and Decision

Chlorpyrifos is an active ingredient in many commonly used insecticides such as Chlorpyrifos, Govern, Hatchet, Lorsban, Lorsban Advanced, Vulcan, Warhawk, Whirlwind and Yuma, and formulated mixtures such as Bolton, Cobalt Advanced, Match-Up, and Stallion. It is a neurotoxic chemical capable of affecting a wide range of animals including many arthropod pests, but also humans and non-target organisms. Chlorpyrifos interferes with the normal functioning of their nervous systems by binding to acetylcholinesterase (AChE), preventing the breakdown of acetylcholine. Subsequent accumulation of acetylcholine causes over stimulation of nerves which can result in paralysis and death. Chlorpyrifos is also a source of contamination in multiple surface water bodies in Minnesota and can pose a substantial risk to human health and the environment.

In 2007, the Natural Resources Defense Council (NRDC) and Pesticide Action Network North America (PANNA) submitted a petition to the Environmental Protection Agency (EPA) to revoke all tolerances and cancel all registrations for chlorpyrifos based on adverse human health effects. The EPA made a final decision, denying this petition in 2019. However, in a ruling issued on April 29, 2021, the Ninth Circuit Court of Appeals vacated the 2019 denial of the petition and instructed the EPA to either modify chlorpyrifos’s tolerances and publish findings to show they are safe, including for infants and children, or to revoke all chlorpyrifos tolerances within 60 days. The EPA announced on August 18, 2021 that “Based on the currently available data and taking into consideration the currently registered uses for chlorpyrifos, EPA is unable to conclude that the risk from aggregate exposure from the use of chlorpyrifos meets the safety standard of the Federal Food, Drug, and Cosmetic Act (FFDCA). Accordingly, EPA is revoking all tolerances for chlorpyrifos.” The revocation of all tolerances will take effect six months after the publication of the final rule. Therefore, growers can still use chlorpyrifos through this 2021 growing season.

Alternatives to Chlorpyrifos

Chlorpyrifos is widely used in Minnesota to manage a variety of arthropod pests in several important agricultural crops. For example, chlorpyrifos is used to manage soybean aphids which can reduce soybean yield up to 40%. Based on United States Department of Agriculture (USDA) National Agricultural Statistics Service (NASS) and Minnesota Agricultural Statistics Service (MASS) surveys conducted between 2013 and 2018, chlorpyrifos was applied on approximately 11% of soybean acres, 9% of wheat acres, and 1% of hay acres and corn acres in Minnesota. NASS and MASS do not collect pesticide use data for all crops; however, chlorpyrifos is used on a notable portion of acres for other crops in Minnesota such as sugar beets (~15% of acres), dry beans (~15% of acres) and sunflowers.

Chlorpyrifos is one pest management option among others for many crop pests. The Extension crop and pest management guides listed below provide extensive lists of products available for management of pests, but they are not Minnesota-specific, so some of the products listed may not be available or registered for use in Minnesota. You can find out if a pesticide is registered in Minnesota by searching the Minnesota Department of Agriculture’s website. Always read the label before applying a pesticide. These guides can be searched for alternative pesticides to chlorpyrifos. Non-chemical management tactics and prevention measures may also be options for some pests. An additional useful resource is the EPA Pesticide Product Label System website, which houses labels for pesticides.

Field Crops:

https://www.ag.ndsu.edu/publications/crops/north-dakota-field-crop-insect-management-guide

Vegetable Crops:

https://mdc.itap.purdue.edu/item.asp?Item_Number=ID-56

Fruit Crops:

https://edustore.purdue.edu/item.asp?Item_Number=ID-465-W

Example: Alternatives for soybean aphid and twospotted spider mites in soybean

As mentioned above, EPA indicates that growers can still use chlorpyrifos through the end of the 2021 growing season. In coming years, however, farmers will need to consider alternative insecticides or other management tactics for some pests. As an example, soybean is one crop that often requires foliar applications of insecticides. The table below summarizes insecticide alternatives to chlorpyrifos for management of soybean aphid and twospotted spider mites in soybean. Products are mentioned in the tables for illustrative purposes only and may not represent a complete list of options available. Inclusion of products does not mean endorsement and their absence does not imply disapproval. Always read and follow label directions. Other non-chemical management tactics may also be considered for some of these pests (see other related Extension publications).

Table 1. Alternatives to chlorpyrifos for management of two key soybean pests: soybean aphid and twospotted spider mite. This list of products was compiled primarily from NDSU and Purdue extension publications. These references can be referred to for alternatives to chlorpyrifos for other pests in soybean as well.