A new study revealed that the world's best-selling and most commonly-used insecticides, neonicotinoids, could impair the ability of the queen bees to lay eggs and maintain healthy bee colonies.
The study, published in the journal Scientific Reports, showed that queen bees exposed to imidacloprid, which belongs to a popular class of nicotine-based insecticides known as neonicotinoids, have substantially laid fewer eggs. It was revealed that the queen bees lay about one-third to two-thirds less than their normal egg production, depending on the imidacloprid doses used in the colonies.
"The queens are of particular importance because they're the only reproductive individual laying eggs in the colony," said Judy Wu-Smart, assistant professor of entomology and lead author of the study, in a press release. "One queen can lay up to 1,000 eggs a day. If her ability to lay eggs is reduced, that is a subtle effect that isn't (immediately) noticeable but translates to really dramatic consequences for the colony."
For the study, the researchers gave colonies populated by 1,500, 3,000 and 7,000 honey bees either a normal syrup or a syrup with imidacloprid in doses of 10, 20, 50 and 100 parts per billion, or PPB.
The researchers discovered that the colonies given with normal syrup have 10 percent empty cells, the signature hexagonal hollows that serve as cribs for honey bee broods. On the other hand, the colonies exposed to 20, 50 and 100 PPB of imidacloprid have 24, 31 and 48 percent empty cells, respectively. This suggests that exposure to imidacloprid promotes poor brood health.
Furthermore, the researchers discovered that the exposed colonies collected and stored far less pollen. Unexposed hives have more than four percent of their cells filled with pollen, while the hives exposed with 10 PBB of imidacloprid have less than one percent of its cell containing pollen.
The hygienic behaviors of bees were also affected by imidacloprid exposure. In a 7,000 -bee colonies, the bees were able to remove more than 95 percent of mite-infested and disease larvae. However, colonies exposed to 100 PBB only eliminated 74 percent of their ailing brood, while a 50 PBB colony just removed about 63 percent.
With their findings, the researchers recommend regulating the use of neonicotinoids to protect bee colonies. They also advise growers to avoid planting seed-treated products to prevent winds from sweeping some the chemicals that can harm the bee colonies.