The widely used pesticides known as neonicotinoids, or neonics, have at least two major problems. First, research shows they contribute to the troubling, ongoing die-off of bees, and may seriously harm birds. Second, like other pesticides, they’re becoming less effective as the insects they target develop resistance.

Faced with those realities, the U.S. Environmental Protection Agency in 2013 approved a new pesticide called sulfoxaflor as an alternative. In response, beekeepers and environmental groups sued the agency, arguing that there wasn’t evidence to support the safety of an insecticide that the EPA’s own assessment found was “very highly toxic” to bees. A federal court agreed, overturning the agency’s approval of sulfoxaflor. More recently, the EPA has allowed farmers to apply the chemical to some crops that don’t attract bees, and has granted emergency waivers when older insecticides are no longer a match for resistant aphids and other pests on crops like sorghum and cotton.

Now, despite concerns that its impacts aren’t well understood, sulfoxaflor is going mainstream. On July 12, the EPA said it will allow farmers to spray the chemical on a variety of crops, including alfalfa, corn, soybeans, citrus, strawberries, squash, and watermelons. The decision was based on new data submitted by Corteva Agriscience, sulfoxaflor’s manufacturer, and “shows the agency’s commitment to making decisions that are based on sound science,” an EPA press release said.

But environmental groups say sulfoxaflor remains too little studied, and that, far from justifying such a sweeping expansion of its use, early research raises red flags about the chemical’s ecological impacts. “This announcement really concerns me,” says Nicole Michel, a National Audubon Society quantitative ecologist who has studied the ecological effects of pesticides. “I don’t feel that they have done the studies necessary to feel confident this pesticide is safe.”

The change clears farmers to use sulfoxaflor on roughly 200 million acres nationwide, according to Nathan Donley, a senior scientist with the Center for Biological Diversity. “What worries me is the scale of that,” Donley says. “The ecological effects that can happen over that large an area of land could be potentially disastrous.”

Sulfoxaflor is closely related to neonics. Typically applied as a coating on seeds, neonics are insect neurotoxins that spread throughout plants, including their pollen and nectar. Research has shown they hurt reproduction in honeybees and wild bees, and can be toxic to aquatic insects. Neonics have been partially banned in the European Union, are being phased out in Canada, and are under review in the United States.

The EPA touts sulfoxaflor as a safer alternative to neonics, saying it doesn’t persist as long in the environment and is a necessary tool for farmers facing resistant pests. But the chemicals work in similar ways; the EPA considers sulfoxaflor part of a new “subclass of the neonicotinoid insecticides.” Christy Morrissey, a University of Saskatchewan ecotoxicologist who studies pesticides, says that sulfoxaflor, like neonics, lingers a long time in water bodies, exposing aquatic insects to low but long-term doses of the chemical. “I remain skeptical that they are as safe as described,” she wrote in an email, referring to both neonics and sulfoxaflor. Other research published last year showed that sulfoxaflor significantly hurt reproduction in exposed bumble bees, suggesting this replacement for neonics might not be any better for the pollinators.

Environmentalists worry that the same might be true for birds. Morrissey’s research links neonic exposure to reduced fat stores and trouble with navigation, making already perilous migrations more dangerous for birds. The chemicals can also make it harder for birds to find food, Audubon’s Michel says. “These insecticides do what they say: They kill insects,” she says. “It just so happens that the insects most vulnerable to neonic pesticides include chironomids, the midges”—an important food source for swallows, swifts, and other insect-eating birds.

The EPA’s risk assessment says that, while sulfoxaflor can be lethal to birds at high enough doses, it poses little threat to them overall. But that conclusion draws on lab tests with just three species: Mallard, Northern Bobwhite, and Zebra Finch. Donley says those avian guinea pigs don’t fully represent the hundreds of species that could be exposed in the field. “They’re certainly underestimating the harm that will come to some bird species,” he says. The agency also hasn’t assessed what risks sulfoxaflor could pose to birds and other wildlife protected by the Endangered Species Act, which he calls “extremely problematic.” 

Donley says he’s concerned not only that there isn’t enough science on sulfoxaflor to justify the agency’s decision, but that, as he puts it, “the EPA has relied solely, completely, 100 percent on industry studies” to greenlight the insecticide. Dow Chemical, a forerunner of sulfoxaflor manufacturer Corteva’s parent company DowDuPont, made a $1 million contribution to President Trump’s inaugural committee, Donley notes. 

Since then, the Department of Justice allowed Dow to merge with DuPont, and the EPA stopped a planned ban on chlorpyrifos, another of the company’s pesticides that has been linked to impaired brain development in children. A court later ordered the agency to ban chlorpyrifos; the EPA appealed and was given until this month to respond to objections to its approval of the chemical. Last week, the agency brushed aside those objections and said it will not ban chlorpyrifos.

As farmers begin using sulfoxaflor more widely, another recent Trump administration decision could make the chemical’s ecological impacts harder to measure: A few days before the EPA lifted restrictions on the bee-killing chemical, the U.S. Department of Agriculture suspended a program that monitors honeybee populations.


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