The results of their experiments, detailed in this week’s issue ofthe Journal of Experimental Biology , have implications for what pesticides should be applied tobee-pollinated crops and shed light on one of the main culpritssuspected to be behind the recent declines in honey bee colonies. Since 2006, beekeepers in North America and Europe have lost aboutone-third of their managed bee colonies each year due to”colony collapse disorder.” While the exact cause isunknown, researchers believe pesticides have contributed to thisdecline. One group of crop pesticides, called”neonicotinoids,” has received particular attention frombeekeepers and researchers. The UC San Diego biologists focused their study on a specificneonicotinoid known as “imidacloprid,” which has beenbanned for use in certain crops in some European countries and isbeing increasingly scrutinized in the United States. Jewelry Packaging Boxes
“In 2006, it was the sixth most commonly used pesticide inCalifornia and is sold for agricultural and home garden use,”said James Nieh, a professor of biology at UC San Diego who headedthe research project with graduate student Daren Eiri, the firstauthor of the study. “It is known to affect bee learning andmemory.” The two biologists found in their experiments that honey beestreated with a small, single dose of imidacloprid, comparable towhat they would receive in nectar, became “picky eaters.” “In other words, the bees preferred to only feed on sweeternectar and refused nectars of lower sweetness that they wouldnormally feed on and that would have provided important sustenancefor the colony,” said Eiri. “In addition, bees typicallyrecruit their nestmates to good food with waggle dances, and wediscovered that the treated bees also danced less.” The two researchers point out that honey bees that prefer only verysweet foods can dramatically reduce the amount of resources broughtback to the colony. Further reductions in their food stores canoccur when bees no longer communicate to their kin the location ofthe food source. “Exposure to amounts of pesticide formerly considered safe maynegatively affect the health of honey bee colonies,” saidNieh. Acrylic Jewelry Stands
To test how the preference of sugary sources changed due toimidacloprid, the scientists individually harnessed the bees soonly their heads could move. By stimulating the bees’ antennae withsugar water, the researchers were able to determine at whatconcentrations the sugar water was rewarding enough to feed on.Using an ascending range of sugar water from 0 to 50 percent, theresearchers touched the antennae of each bee to see if it extendedits mouthparts. Bees that were treated with imidacloprid were lesswilling to feed on low concentrations of sugar water than thosethat were not treated. The biologists also observed how the pesticide affected the bees’communication system. Jewelry Display Stands
Bees communicate to each other the locationof a food source by performing waggle dances. The number of waggledances performed indicates the attractiveness of the reward andcorresponds to the number of nestmates recruited to good food. “Remarkably, bees that fed on the pesticide reduced the numberof their waggle dances between fourfold and tenfold,” saidEiri. “And in some cases, the affected bees stopped dancingcompletely.” The two scientists said their discoveries not only haveimplications for how pesticides are applied and used inbee-pollinated crops, but provide an additional chemical tool thatcan be used by other researchers studying the neural control ofhoney bee behavior.
The study was funded by the North American Pollinator ProtectionCampaign and the National Science Foundation.