The Environmental Protection Agency once again has reversed course and will revoke the use of the insecticide chlorpyrifos that's applied to food crops because it causes neurological damage in exposed farm workers and children that eat food with its residue, according to the federal agency. The final rule previewed today will end its use on crops used for food, fruits and vegetables six months after its publication in the Federal Register, the EPA said.
It is still reviewing its use for non-agriculture uses, such as mosquito control and animal protection insecticides. More complete information can be found on the EPA's website here. A copy of the pre-publication of the rule can be found here.
Corteva Agriscience, once the world’s largest manufacturer of chlorpyrifos, said last year it would stop manufacturing it, though it stood by the chemical’s safety’s record. Still, some chemical and agricultural businesses have fought to keep it on the market, given its effectiveness.
The EPA’s decision marked the end of years of agency reviews, preliminary decisions and court challenges. In 2015, the EPA proposed prohibiting the insecticide, but later changed course, pointing to concerns from USDA officials about the negative impact of the restrictions on farmers. The EPA did not comment on this concern in its decision today. The American Farm Bureau Federation also expressed its concerns with the decision.
The IFBF said in 2018 that is was concerned about the underlying science and methodologies used in the agency's biological evaluation in an endangered species review that could lead to unsound modeling and regulation of crop protection compounds in the future. Its loss was considered as potentially devastating to Iowa crop producers, particularly soybean growers. The IFBF strongly opposed the revocation of all tolerances for chlorpyrifos.
Chlorpyrifos use on Iowa soybeans has ranged from 3-14 percent of the crop in recent years. Variation in use is due to variable annual weather and the use of genetically modified crops. It is currently used primarily to treat soybean aphid infestations that have become the dominate soybean insect pest in Iowa since 2000, according to Iowa State University entomologists and growers.
Infestations are sporadic and unpredictable, but aphids have the ability to cause significant yield loss (as high as 40 percent in the Midwest) during periods of optimal reproduction. Due to its fast knockdown and control of other pests (such as spider mites and Japanese beetles), chlorpyrifos is the leading product used to control soybean aphids. Chlorpyrifos is also an important active ingredient to control a variety of other crop insects. Its average annual use varies based on weather and pest conditions, but can be used on an estimated average of at least 800,000 acres of diversified Iowa crops, according to industry sources.
Many of the farms that use it today are smaller operations that have fewer resources to absorb the additional cost of limited, more expensive, less effective, alternative products. It is used, as needed, on alfalfa, corn (for forage, grain, oil, stover, and sweet corn), cucumbers, grapes, pumpkins, sorghum (for forage, grain and stover), soybeans, and wheat (for forage, grain and straw). Chlorpyrifos is also used on grain crops that are fed to egg-laying poultry, and cattle, goats, hogs, poultry and sheep grown for meat and meat byproducts.
Iowa farmers and certified crop consultants scout their fields and only use the product judiciously and according to the product label. If economic thresholds are exceeded, chlorpyrifos is a very safe and cost-effective, science-based crop protection strategy when label directions are followed. But due to the high reproductive capacity and migratory movements of aphids, more than one application may be necessary in a single growing season. If this happens, entomologists recommend rotating modes of action to prolong its effectiveness and to prevent developing genetic resistance.
Losing the use of chlorpyrifos will increase the likelihood of pest resistance developing among the remaining alternative, more persistent and expensive products, resulting in other possible unintended biological and environmental consequences. Increased adoption of genetically modified corn with traits resistant to corn rootworm and European corn borer has significantly reduced the need to apply insecticides on Iowa corn.
Chlorpyrifos is applied to only an estimated 100,000 acres of corn today, or less than 1 percent of Iowa corn acres. Crop rotation away from corn for one year is generally an effective, nonchemical rootworm control practice for traditional, non-GMO hybrid corn in Iowa. But when corn is planted each year on the same acreage, soil-applied insecticides - predominantly organophosphates that include chlorpyrifos - are applied to control rootworm larvae damage when necessary. Because this product is broad spectrum and also controls cutworm at planting time, it actually prevents the need for additional rescue treatments later in the growing season. This is a tremendous environmental benefit.