WASHINGTON — A common type of pesticide is dramatically harming wild bees, according to a new in-the-field study that outside experts say may help shift the way the U.S. government looks at a controversial class of chemicals.

But in the study published by the journal Nature on Wednesday, honeybees – which get trucked from place to place to pollinate major crops like almonds – didn’t show the significant ill effects that wild cousins like bumblebees did. This is a finding some experts found surprising.

A second study published in the same journal showed that in lab tests, bees are not repelled by the pesticides and in fact may even prefer pesticide coated crops, making the problem worse. Bees of all kinds – crucial to pollinating plants, including major agricultural crops – have been in decline for several reasons. Pesticide problems are just one of many problems facing pollinators; this is separate from colony collapse disorder, which devastated honeybee populations in recent years but is now abating, experts said.

Exposure to neonicotinoid insecticides reduced the density of wild bees, resulted in less reproduction, and colonies that didn’t grow when compared to bees not exposed to the pesticide, the study found.

Scientists in Sweden were able to conduct a study that was in the wild, but still had the in-the-lab qualities of having control groups.