Scientists say a widely used pesticide can affect honeybees’ ability to fly, making it harder for foraging bees to find their way home. They published their findings in the journal Scientific Reports.

Bee populations worldwide are currently facing a mountain of threats and difficulties. Parasites, habitat loss, and even antibiotics have all been implicated in the bees’ decline, but it may be pesticide that’s doing the most damage.

Foraging honeybees (Apis mellifera) regularly take in small amounts of chemicals like thiamethoxam, a neonicotinoid pesticide that’s regularly sprayed on monoculture crops like cotton, soybeans, and corn. A little dose won’t kill the bees, and it won’t keep them from coming back to consume more the next day. Over time, that chronic exposure can mess them up.

Biologists at the University of California San Diego’s Nieh Lab wanted to know if and how thiamethoxam could affect bees’ ability to fly. They exposed honeybees to low doses of the pesticide for two days, then strapped each one into this unusual contraption—the bee version of a treadmill.

At first, the pesticide almost seemed like it was doing the bees a favor. Thiamethoxam-exposed bees initially flew much farther and faster than bees who’d never been near the chemical.

The problem is that they weren’t flying anywhere in particular. They seemed disoriented and soon wore themselves out in their mad, flailing dash to get where they wanted to go. On the treadmill, this panic-type flying didn’t do them any harm, but in the wild, these erratic, exhausting flight patterns could keep the bees from ever getting home.

To make matters worse, given a choice, the bees almost always opted to consume pesticide, and they ate more when their food had been laced with the stuff.

"The honey bee is a highly social organism, so the behavior of thousands of bees are essential for the survival of the colony," co-author James Nieh said in a statement. "We've shown that a sub-lethal dose may lead to a lethal effect on the entire colony."

Header image by Luc Viatour via Wikimedia Creative Commons // CC BY-SA 3.0