The new limits would be among the nation’s most extensive for agricultural use of neonicotinoids, a class of insecticides used to kill plant-damaging pests like aphids. The highly potent pesticides have been shown to harm bees, birds, and other creatures.

Aimed at protecting bees that pollinate crops, the California Department of Pesticide Regulation’s proposed rules would restrict four closely-related neonicotinoid chemicals: imidacloprid, thiamethoxam, clothianidin, and dinotefuran.

Unveiled in February, the rules would limit when and how much can be applied, depending on the specific chemical, the crop and, in some cases, the presence of honeybees or other pollinators. California’s pesticide regulators are still evaluating public feedback and there is no specific timeframe for finalizing the proposal.

Neonicotinoids are the most popular insecticides in the world—although not in California, according to the state pesticide agency.

More than a decade in the making, California’s reevaluation of neonicotinoids began in 2009, after the agency received a report from pesticide manufacturer Bayer CropScience that “showed potentially harmful effects of imidacloprid to pollinators.” A 2014 law set a series of deadlines for reevaluating their risks and adopting “any control measures necessary to protect pollinator health.”

In addition, a bill in the Legislature would ban use of neonicotinoids in homes, yards, and other outdoor non-agricultural settings, starting in 2024. A variety of consumer products are registered for use in California, such as BioAdvanced All-in-One Rose and Flower Care Liquid Concentrate, which contains imidacloprid.

The bill trails other states, including New Jersey and Maine, that have already banned outdoor uses in gardens and residential areas. New Jersey’s ban extends to commercial landscapes, like golf courses, too.

The European Union banned several neonicotinoids for all outdoor uses because of the risks to bees. And other states already have some restrictions on agricultural use, largely by allowing the chemicals to be bought or used only by those with specific training. Rhode Island has also barred neonicotinoids when crops are blooming.

If finalized, California’s proposal to restrict agricultural use could “significantly impact when and how” neonicotinoid products can be used in the nation’s No. 1 agricultural state, according to an analysis by the California Department of Food and Agriculture. 

“This is critical,” said Karen Morrison, acting chief deputy director of the Department of Pesticide Regulation. “Pollinators play a very important role in the ecosystem at large as well as for crops and being able to produce food in the state.”

California regulators anticipate the rule would reduce neonicotinoids applied to plants and soil by 45 percent. Seeds coated in neonicotinoids—a major use of the chemicals—would not be restricted.

California growers say the restrictions could hamstring their power to protect crops and could ultimately lead to worse outcomes for pollinators.

Limiting the use of neonicotinoids could force the citrus industry, for instance, to use other pesticides that are “not necessarily what the state of California wants” and could require “multiple sprays, something that may pose more risk to bees,” said Casey Creamer, president and CEO of California Citrus Mutual, a trade association of citrus growers.

Almonds, cherries, citrus, cotton, grapes, strawberries, tomatoes, and walnuts are major crops expected to be highly affected by the restrictions. These crops make up about half of the state’s agricultural exports and two-thirds of the acreage treated with neonicotinoids from 2017 to 2019. Fresno, Kern, Tulare, Monterey, and San Joaquin top the list of counties where the most neonicotinoids were applied.

Some replacement chemicals may be more toxic to pests’ natural enemies—worsening infestations, the California agriculture department warned in its analysis.

Such alternatives like pyrethroids, for instance, are also “very toxic to bees, in that they hit the bee, the bee dies. If they’re in the spray, they all die,” said Robert Van Steenwyk, a cooperative extension specialist emeritus at the University of California, Berkeley and one of the authors of the report. “So, that isn’t a great alternative.”

The regulation contains some exceptions to allow neonicotinoids for invasive pests like the Asian citrus psyllid, which spreads citrus greening disease.

Though the California agriculture department does not anticipate any crop losses, its experts do expect an increase in costs because of the price of replacement pesticides.

The eight highly affected crops collectively earned nearly $19 billion in revenue in 2019, according to the assessment by the California agriculture department. Had the regulations been in place, costs to the growers would have ranged between $13.3 million in 2017 to $12.1 million in 2019.

Representatives of pesticide manufacturer Bayer CropScience raised several concerns about the proposal in a letter to the pesticide agency, including that it “is not grounded in science.” In addition, the proposed pesticide application rates “are not efficacious and therefore will not provide control of target pests” on some crops, the company said.

Birds, Bees, and Aquatic Life

Inspired by the toxicity of nicotine, neonicotinoids coat crop seeds, are sprayed on plants and drench the soil in fields. The chemicals suffuse the plant and its pollen and nectar, attacking the central nervous systems of insects.

As their use has climbed, so too have studies revealing that they threaten birds, bees, and aquatic creatures. Potential human health risks remain under investigation.

Wild bees living and foraging near crops grown from neonicotinoid-treated seeds showed large population die-offs in a study funded by pesticide manufacturers.

Honey bees are reared and managed for their honey production and ability to pollinate crops, among other services. Research shows the insecticides kill worker bees, reduce immunity of the hive and leave colonies without their queens.

The insecticides also decimate zooplankton and therefore the fish that feed on them. Birds stop eating, and delay migration. In an assessment of three of the chemicals, the U.S. Environmental Protection Agency found they are likely to harm between 67 percent and 79 percent of federally endangered or threatened species and between 56 percent and 83 percent of their critical habitats.

Part of the problem is that the chemicals don’t stay put. They “can move from treated plants to pollinators and from plants to pests to natural enemies,” wrote entomology professors Steve Frank at North Carolina State University and John Tooker of Pennsylvania State University in the journal PNAS in 2020. “We believe that neonicotinoids pose broader risks to biodiversity and food webs than previously recognized.”

The chemicals are turning up in groundwater and surface water, including 93 percent of water samples pulled from creeks, rivers, and runoff in Southern California and 97 percent of samples drawn from agricultural stretches of the Central Coast and Southern California.

Jacob Cecala learned that neonicotinoids are far more toxic to bees than he anticipated during his graduate research at the University of California, Riverside.

A month after he treated native plants from a California nursery with the neonicotinoid imidacloprid, following the label instructions exactly, Cecala discovered that all his bees were dying—their little bodies still on the flowers.

His goal had been to study the non-fatal effects of the pesticide on a species of bee used for pollinating alfalfa crops. “I was like, ‘Oh my god, what am I going to do? How am I going to complete my dissertation?’” Cecala said.

It took him another year—and cutting down the amount of pesticide by two-thirds—to find out that although more bees survived, the survivors still stopped foraging for food as much and their reproduction dropped drastically.

“Bees are insects—they’re just as susceptible to these compounds as an aphid or some other insect pest would be,” said Cecala, who is now a postdoctoral scientist at the University of California, Davis. “That’s where the problem lies.”

‘Some Very Concerning Gaps Remain’

“As is often the case, California is leading the way with the first state regulatory system for neonics in the nation,” said Daniel Raichel, acting director of the Natural Resources Defense Council’s pollinator initiative. “It’s an important first step—especially in regards to pollinator protection—but some very concerning gaps remain.”

California does not address, for instance, crop seeds coated with neonicotinoids, which permeate the plant as it grows but also seep into water, soil, and other plants. Coated seeds “may introduce a significant contribution of pesticide mass that remains unreported” in California, state officials said in a November workshop.

But the state doesn’t regulate treated seeds as pesticides and found that the seeds don’t pose a significant risk to pollinators, Morrison said, although she added, “this is an area that we’re actively looking at.”

Environmentalists also raised concerns that the proposal is primarily aimed at reducing risk to carefully tended hives of honeybees—not its native bee species and other pollinators.

But state officials said even though their assessment analyzed the risks to honeybees, the rules would protect wild bees, too.

The proposal bars spraying plants and drenching soil with neonicotinoids when crops that are attractive to bees are blooming, and sets a cap for seasonal application. It also establishes crop-specific restrictions on application rates and timing that, for crops moderately attractive to bees, only apply when hives of honey bees or other managed pollinators are on the field.

“Honey bees are actually pretty odd as far as bees go,” Cecala said. They make honey, for one thing, and live in hives. The consequences of pesticide exposure can be much more drastic for California’s solitary bees. If a solitary mother bee “gets exposed to a pesticide and she is not able to reproduce, that essentially ends her entire genetic line,” Cecala said.

Legislators are considering closing one gap environmental groups have identified in California’s draft regulation: non-agricultural use of the pesticides, including in gardens and commercial landscapes like golf courses. These account for 15 to 20 percent of known neonicotinoid use in California, according to a legislative analysis of the bill.

The bill, which contains exceptions for veterinary use and indoor pest control, is set to be triaged by the Senate Appropriations Committee in August, when it decides which bills will survive and which will die.

Assemblymember Rebecca Bauer-Kahan, a Democrat from San Ramon and author of the bill, said other states have already taken the lead on banning the use of these chemicals in households and neighborhoods.

“We’re not leading the way,” she said. “We’ve got to get our act together!”

This article originally appeared in CalMatters, and is reprinted with permission.