By Ashley Dean, Education Extension Specialist and Erin Hodgson, Professor, Iowa State University

Chlorpyrifos (e.g., Lorsban and Warhawk) is an organophosphate (Group 1B) insecticide that has been used for many important field crop pests in the United States. In the past 15 years, chlorpyrifos, like many organophosphates, has come under scrutiny due to acute toxicity concerns to humans, especially children. In an effort to protect all ages of humans and the environment, EPA began the process of phasing out many uses of organophosphates. On August 18, 2021, the EPA announced their decision to revoke tolerances for chlorpyrifos.

As of February 28, 2022, the EPA has revoked all food tolerances for chlorpyrifos. This means there is no longer any allowable chlorpyrifos residue for food products where chlorpyrifos was applied on or after February 28, 2022. Farmers may no longer apply pesticide products containing chlorpyrifos on crops grown for any food or feed use.

List 1 shows commodities for which uses are impacted by tolerance revocation. In Iowa, the relevant field crop uses that are impacted include: alfalfa, corn (field, sweet, and any for seed), soybean, sorghum, and wheat, as well as seed treatments. The list includes livestock uses and many horticultural crops that may be grown in field or greenhouse settings within Iowa, so please check the list in case your operation includes such commodities. See List 2 for a list of commodities that are not impacted by tolerance revocation. This list includes ear tags for cattle so long as certain conditions are met.

Common Questions:

Why revoke this insecticide? This decision follows a lengthy evaluation of the safety of chlorpyrifos from exposure via food, drinking water, and residential uses. EPA’s evaluation suggests that currently registered uses may exceed a safe level of exposure and likely cause adverse side effects, especially to children.

For what uses have tolerances been revoked? All tolerances have been revoked for food uses, including feed (List 1). Currently, non-food uses are still allowed, but the registration review process is ongoing, and EPA will decide soon about the remaining uses of chlorpyrifos. Sometimes, food crops also have non-food uses. EPA provides some examples of such commodities and relevant restrictions in a set of frequently asked questions.

What to do if you are in possession of chlorpyrifos products: If you have products containing chlorpyrifos in your possession, do not use these products on food or feed crops going forward.

  • After February 27, 2022, any chlorpyrifos products with food uses on the label are considered “misbranded,” and it is illegal to sell and distribute those products.
  • Labels will need to be amended to remove food uses that were cancelled when tolerances were revoked.

Disposal: Do not dispose of chlorpyrifos products in landfills. Currently, the state of Iowa does not have a plan for disposal of chlorpyrifos products. Therefore, it is best to either use these products according to the label for non-food uses only or store them until appropriate disposal opportunities are available.

Enforcement: FDA has a 2-stage enforcement approach if chlorpyrifos residues are detected in food products on or after the revocation date (February 28, 2022). This is because chlorpyrifos residues from legal applications made prior to the revocation date may be present in trade channels for different periods of time (i.e., showing dates) depending on application and harvest dates and the duration of storage, distribution, and sale. During Stage 1, companies will not be asked to provide documentation of legal applications when residues are found below the previous tolerance level. After the showing dates, Stage 2 is implemented and documentation of purchase or spraying records may be required when chlorpyrifos residues are found in food products. FDA anticipates that all food made from commodities with legal applications of chlorpyrifos will exit the trade channels by August 28, 2026. To see a list of showing dates see the FDA Q&A document (page 9).

Since several aspects of this decision remain unclear, including disposal of products and whether non-food uses will continue after the registration review process is complete, we intend to post timely updates on ICM News as we learn more. If you would like more information, see the list of resources below.

List 1. Uses impacted by tolerance revocation.
Chlorpyrifos cannot be used for these commodities after February 27, 2022.

Field and Greenhouse Food Crops*

  • Alfalfa
  • Asparagus
  • Banana
  • Bean (snap, lima)
  • Beet (sugar, table, for seed)
  • Blueberry
  • Brassica leafy vegetables, radish (incl. for seed), rutabaga, turnip
  • Caneberry
  • Cherimoya
  • Citrus and citrus orchard floors**
  • Corn (field, sweet, for seed)
  • Cotton
  • Cranberry
  • Cucumber
  • Date
  • Feijoa
  • Fig
  • Grape
  • Kiwifruit
  • Leek
  • Mint
  • Onion (dry bulb)
  • Pea
  • Peanut
  • Pepper
  • Pumpkin
  • Sapote
  • Seed and pod vegetables
  • Seed treatments
  • Sorghum (grain, milo)
  • Soybean
  • Strawberry
  • Sugarcane
  • Sunflower
  • Sweet potato
  • Tree fruits (apple, cherry, nectarine, peach, pear, plum, prune)**
  • Tree nuts (almond, filbert, pecan, walnut)**
  • Wheat

Livestock

  • Cattle ear tags***
  • Poultry houses
  • Turkey, swine, and dairy barns

*Remember to keep adequate records of chlorpyrifos applications to any of these crops for food or non-food usage in case EPA asks for production of these records. See “Enforcement” section.

** Unless made to non-bearing trees that will not bear fruit within a year.

*** Except beef and non-lactating dairy cattle and cattle in mating and cow-calf operations if ear tags are removed >1 year prior to slaughter. Remember to keep adequate records of ear tag usage.

List 2. Uses NOT impacted by tolerance revocation.
Chlorpyrifos can still be used on these commodities after February 27, 2022.

  • Christmas tree plantations
  • Commercial ornamentals
  • Commercial sod farms
  • Containerized baits
  • Fence posts, logs, poles
  • Food processing plants
  • Forest tree nurseries and plantations; felled trees; cut stumps
  • Golf courses
  • Grass sown for seed
  • Individual fire ant mounds
  • Industrial plants
  • Landscape timbers
  • Manufacturing plants
  • Mosquito control
  • Non-bearing fruit, nut, or citrus trees
  • Railroad box cars
  • Railroad ties
  • Road medians
  • Ship holds
  • Turf and ornamentals in road medians or industrial sites
  • Underground utility cables and conduits
  • Warehouses
  • USDA quarantine in nurseries and greenhouses (i.e., soil treatment of containers)
  • Tobacco