How bees defend against some controversial insecticides

Honeybees and bumblebees have a way to resist toxic compounds in some widely used insecticides.

These bees make enzymes that help the insects break down a type of neonicotinoid called thiacloprid, scientists report March 22 in Current Biology. Neonicotinoids have been linked to negative effects on bee health, such as difficulty reproducing in honeybees (SN: 7/26/16, p 16). But bees respond to different types of the insecticides in various ways. This finding could help scientists design versions of neonicotinoids that are less harmful to bees, the researchers say.

Such work could have broad ramifications, says study coauthor Chris Bass, an applied entomologist at the University of Exeter in England. “Bees are hugely important to the pollination of crops and wild flowers and biodiversity in general.”

Neonicotinoids are typically coated on seeds such as corn and sometimes sprayed on crops to protect the plants from insect pests. The chemicals are effective, but their use has been suspected to be involved in worrisome declines in numbers of wild pollinators (SN Online: 4/5/12).  

Maj Rundlöf of Lund University in Sweden helped raise the alarm about the insecticides. In 2015, she reported that neonicotinoid-treated crops reduced the populations of bees that fed from the plants. Rundlöf, who was not involved with the new study, says the new research is important because it clarifies differences between the insecticides. “All neonicotinoids are not the same,” she says. “It’s a bit unrealistic to damn a whole group of pesticides.”

Bass and his colleagues, which include scientists from Bayer, one of the main producers of neonicotinoids, investigated resistance to thiacloprid by looking at bees’ defense systems. The team focused on enzymes known as P450s, which can metabolize toxic chemicals, breaking them down before they affect the bee nervous system. The researchers used drugs to inhibit groups of P450 enzymes. When the family enzymes called CYP9Q was inhibited, bees became 170 times as sensitive to thiacloprid, dying from a much smaller dose, the researchers found. Discovering the enzymes’ protective power could lead to more effective ways to simultaneously avoid harming bees and help crops.

“We live in an era that uses pesticides,” Rundlöf says. “We need to figure out the ones that are safest.”