For the First Time, the Government Says a Pesticide Harms Bees

The United States Environmental Protection Agency announced Wednesday that the widely used agricultural pesticide imidacloprid threatens honeybees that help pollinate a third of the world’s food supply.

The EPA’s assessment is the first of four evaluations of neonicotinoids, a class of agricultural insecticides that coat a crop plant’s leaves, stems, and pollen with poison.

Neonics’ long-term impact on pollinators has been a debated issue, and the findings in the report rankled both proponents of neonics and conservation groups that want an outright ban of the pesticides.

That’s because the EPA analysis concluded neonics only affect the health of beehives when the pesticides are applied to cotton plants and citrus trees, not when they are used on corn, leafy vegetables, berries, and tobacco.

RELATED: The Bees Have Their Day in Court—and Win Big

Imidacloprid maker Bayer Crop Sciences claimed in a statement that the EPA’s findings “overestimate the potential for harmful exposures in certain crops” while ignoring its benefits.

But bee advocates say the study doesn’t look at the whole pollinator picture, leaving wild bees—which studies have shown are more sensitive than honeybees to pesticides—at risk.

“You can’t claim to do a ‘pollinator risk assessment’ and really only look at one pollinator, the honeybee,” said Lori Ann Burd, environmental health director at the Center for Biological Diversity. “That’s not only cheating on the purpose of this work but also cheating the native bees, birds, butterflies, and other species threatened by this pesticide.”

In its tests, the EPA found that if the nectar bees brought back to the hive contained more than 25 parts per billion of imidacloprid, effects such as fewer bees in the hive and a drop in honey production were “likely to be seen.”

The EPA conducted the research with the California Environmental Agency and collaborated with Canadian authorities on a similar study that also was also released on Wednesday.

The EPA is working on studies that will examine the impacts of three other commonly used neonics. Those findings should be released by the end of the year.

Last year, the EPA proposed a ban on the use of many pesticides when crops are in bloom and commercial honeybees are present. Fearing crop losses, European authorities last year suspended a neonic ban that had been imposed in 2013.