Common insecticides may harm three-fourths of endangered species

EPA says three chemicals used to protect crops from insects are likely harmful to 1,300 plants and animals and half of the critical habitats protected under the Endangered Species Act

WASHINGTON, D.C.– Three insecticides widely used in California and Tulare County are likely harmful to three-fourths of all endangered plants and animals, according to a recent review by the Environmental Protection Agency.

On June 16, the EPA released its final biological evaluation for the chemicals clothianidin, imidacloprid, and thiamethoxam, part of a group of insecticides known as neonicotinoids. Neonicotinoids are insecticides that affect the central nervous system of insects. The chemicals are applied to leaves of many crops grown in the Valley, such as fruits, nuts and cotton.

The EPA’s assessments of clothianidin, imidacloprid and thiamethoxam marked the first time the agency has completed biological evaluations of any neonicotinoids’ harms to the nation’s most imperiled plants and animals, according to the Center for Biological Diversity. The national, nonprofit conservation and environmental group said species found to be harmed by all three of the neonicotinoids include all 39 species of endangered amphibians, such as the California red-legged frog, as well as rusty patched bumblebees, whooping cranes, chinook salmon, northern long-eared bats and orcas.

“These deeply troubling findings leave no doubt that these dangerous pesticides are silencing the songs of frogs, the flutter of butterfly wings and the buzz of bees,” said Lori Ann Burd, environmental health director at the Center for Biological Diversity. “Many of the species harmed by neonicotinoids are experiencing precipitous declines, and this EPA’s choices may well determine whether or not they go extinct.”

The EPA’s announcement comes after two years of public comments and studying the chemicals’ effects on 1,700 plants, animals and insects and more than 800 critical habitats across the nation. The recently released biological evaluations found that 67% of all endangered species — 1,225 different plants and animal species — are “likely to be adversely affected” by clothianidin and that the pesticide will likely adversely modify the designated critical habitats of 446 species. In Tulare County, the chemical is most commonly used on almonds, walnuts and grapes and to control cockroaches, according to the Department of Pesticide Regulation’s California Pesticide Information Portal.

Imidacloprid, an insecticide used locally on citrus, grapes and cotton, may harm 1,445 species, about 80% of all endangered plants and animals and 658 habitats of endangered animals. Thiamethoxam was found to be harmful to 1,396 species, or 77% of all endangered species and critical habitats of 644 species. In Tulare County, the chemical is most commonly applied to citrus and grapes.

Because of these findings, EPA has begun talks with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service. EPA will be working with both agencies throughout their process to draft biological opinions on the regulation of the chemicals. 

The EPA anticipates releasing amended rules in 2023, which will include updates to some of the previously proposed mitigations to reduce neonicotinoid exposures for listed species. Mitigation measures will be finalized in 2024. 

Neonicotinoids, which are banned in the European Union, are the most popular insecticides in the United States. Environmental groups, like the Center for Biological Diversity, say hundreds of studies have shown they play a major role in population-level declines of bees, birds, butterflies and freshwater invertebrates. More recent studies are showing they cause significant harm to mammals as well.

Bee-ing Cautious

In California, neonicotinoids are widely used as an alternative to chlorpyrifos, which the California Department of Pesticide Regulation (DPR) banned in 2020. The insecticides can accumulate in pollen and nectar of treated plants, which may be a source of exposure to pollinators. Neonicotinoids have been associated with some bee kill incidents. 

Earlier this year, in an effort to reduce risks to bees, the DPR took the first step to limit how and when neonicotinoids can be used in agricultural settings. The proposed regulations would create new requirements and restrictions for the use of neonicotinoid products containing imidacloprid, thiamethoxam, clothianidin and dinotefuran. DPR estimates the regulations will impact 57 products currently registered in California and will reduce the amount of neonicotinoids applied across the state by approximately 45%.

The regulations include tiered restrictions based on the chemical used, the type of crop and the time of year the neonicotinoid is applied in order to protect pollinator health. For example, applications to certain flowering plants that are attractive to bees would be prohibited when the plants are in bloom and when bees may be foraging. The regulations also set limits on applications of multiple neonicotinoids and what application methods may be used by growers. They also include an exemption for quarantine pests to provide the option, if necessary, to treat pests that can severely damage crops and food supply chains. The regulations address both risks to bees and ensures the protection of pollinators critical to growers and the agricultural sector.

The American bumblebee, once the most common bumblebee species in the United States, has declined by an estimated 89% in just the past 20 years. The Center has petitioned for Endangered Species Act protection for the American bumblebee.

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