Common pesticides used to keep apples, broccoli, corn and other crops insect-free may be causing severe learning and memory deficits in honeybees.
Researchers from the University of Otago collected honeybees from 51 hives across 17 locations in the province of Otago in Southern New Zealand. Low levels of pesticides were detected at three of the 17 sites and in six of the 51 hives they examined. Their findings suggest that even the smallest doses of the pesticide chlorpyrifos can be devastating to the success and survival of honeybees.
To test its effects, researchers fed this potent and mobile pesticide to a number of lab bees and put them through a series of learning performance tests. This revealed chlorpyrifos-fed bees had worse odor-learning abilities and could not remember familiar odors, even though they were fed doses that are considered "safe" to spray on crops. This largely effects a honeybee's ability to find nectar and pollinate flowers.
"For example, the dosed bees were less likely to respond specifically to an odor that was previously rewarded," lead author Elodie Urlacher said in a news release. "As honeybees rely on such memory mechanisms to target flowers, chlorpyrifos exposure may be stunting their effectiveness as nectar foragers and pollinators."
Therefore, researchers suggest enforcing a new threshold of 50 picograms of chlorpyrifos be ingested per bee to avoid lethal impacts. Their findings were recently published in the Journal of Chemical Ecology.
"This amount is thousands of times lower than the lethal dose of pure chlorpyrifos, which is around 100 billionths of a gram. Also, it is in the low range of the levels we measured in bees in the field," Urlacher added. "Our findings raise some challenging questions about regulating this pesticide's use. It's now clear that it is not just the lethal effects on bees that need to be taken into account, but also the serious sub-lethal ones at minute doses."
In addition to remembering familiar odors, some bees rely on what researchers call "search images." The idea is that on each foraging trip, bees retain a mental image of flowers that prove to be a promising source of food. Therefore, a recent study from the University of Cambridge suggests flowers tailor their coloring to attract bees, who, in turn, spread their pollen.
