According to a new study published in the journal Chemosphere, certain insecticides common to U.S. orchards appear to make honey bees substantially less busy — and no, they are not neonicotinoids.
The study suggests that exposure to sublethal doses of insecticides known as pyrethroids may reduce honey bee movement and social interaction.
The authors found that honey bees treated with moderate and high doses of a pyrethroid called esfenvalerate moved 61 and 71 percent less, respectively, than untreated bees over a 24-hour span. Bees exposed to high doses of esfenvalerate and its cousin permethrin also spent 43 and 67 percent less time interacting with their neighbors. The researchers gathered data on the honey bees by recording them on video and tracking their behavior via a software program.
But why, one might ask, would anyone expose bees to pesticides and then be surprised that they were somehow affected negatively?
“I think the issue is not that we are surprised there may be effects, but what is the dose-response relationship?” said Bob Wright, a research and extension entomologist at UNL. “Looking at sublethal effects like behavior is a relatively less well-studied area than straight toxic effects, and using video recordings to analyze behavior is a relatively new technique to look at this for insects.”
Though legislators have put limits on pyrethroid use, the National Agricultural Statistics Service has reported that the insecticides are applied across roughly one million acres of U.S. orchards. Growers regularly place honey bee colonies in these orchards, where pollination improves the yield and quality of crops ranging from almonds and cherries to peaches and pears.
While cautioning that the study was conducted under laboratory conditions, lead author Erin Ingram said that behavioral changes similar to those found by the UNL team would have significant consequences if manifested in natural environments.
“The strength of a (honey bee) colony relies on the proper functioning of its members to perform all of the necessary duties, such as foraging for food and communicating with other bees,” said Ingram, a doctoral student at the University of Nebraska-Lincoln. “If bee locomotion, social interaction, or ability to feed are impaired by sublethal exposure to pesticides, this could potentially impact colony survival or performance. Animal behavior has typically been studied manually through time- and effort-intensive observation. With additional work, this system could potentially be developed into an efficient and relatively cost-effective way to examine changes in honey bee behavior in response to low levels of pesticide exposure as part of the risk assessment process.”
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