(Beyond Pesticides, March 10, 2010) A study investigating the sublethal effects of pyrethroids, bifenthrin and deltamethrin on honeybees finds that the chemicals significantly impair the pollinators’ reproduction. The researchers also point out that the concentration of each pesticide that produced adverse effects in the experiments was at or below those that bees could encounter while pollinating treated crop fields.
“Effects of sublethal concentrations of bifenthrin and deltamethrin on fecundity, growth, and development of the honeybee Apis mellifera ligustica” published in the March issue of Environmental Toxicology & Chemistry, investigated the effects of the two pesticides at sublethal concentrations on fecundity, growth, and development of honeybees were examined with the feeding method for a three-year period (2006-2008). It was shown that both bifenthrin and deltamethrin significantly reduced bee fecundity, decreased the rate at which bees develop to adulthood, and increased their immature periods. Queens in the control group in 2006 laid a little more than 1,200 eggs each day, compared to not quite 900 a day in the bifenthrin group and roughly 600 per day in the deltamethrin group. In general, the hatch rate of pyrethroid-exposed eggs was also significantly depressed. The success rate of hatchlings, that is the share that reached adulthood, varied from 75 to 95 percent in the control hive — making it between 20 and 40 percentage points higher than in hives where bees had been exposed to a pyrethroid. The researchers conclude: “The impact of pesticides on the colony may be severe.”
Both pyrethroids, bifenthrin and deltamethrin, are neurotoxic, typically causing paralysis in target pests. Pyrethroids are synthetic versions of pyrethrin, a natural insecticide found in certain species of chrysanthemum. It initially was introduced on the market as a ”˜safer’ alternative to the heavily regulated and highly toxic organophosphates such as chlorpyrifos and diazinon, which were banned for homeowner use in 2001 and 2004, respectively. Despite the fact that there are plenty of effective pest control methods that are not nearly as toxic, it is now one of the most popular class of household pesticides, available in the form of powders and sprays to control ants, mosquitoes, fleas, flies, and cockroaches. These high-volume uses of pyrethroid pesticides are cause for concern to consumers because of their link to serious chronic health problems. Synthetic pyrethroids are suspected endocrine disruptors, have been linked to certain cancers and are particularly dangerous to aquatic life even at low concentrations.
Research into Colony Collapse Disorder (CCD), the widespread disappearance of honeybees that has killed off more than a third of commercial honey bees in the U.S., has been linked to larval exposure to a cocktail of frequently used pesticides. Research is ongoing as to the cause of the CCD phenomenon, but pesticides have been implicated. CCD can be especially devastating since honeybees are essential pollinators of crops that constitute over one third of the U.S. food supply or $15 billion worth of food.
David Hackenberg, the beekeeper who first discovered a mysterious disappearance of honeybees now known as colony collapse disorder (CCD), is schedule to speak at Beyond Pesticides’ 28th National Pesticide Forum, Greening the Community, April 9-10 at Case Western Reserve University in Cleveland, OH. Mr. Hackenberg believes that pesticides contribute to CCD and that honeybees are a barometer of the environment. Featured in several films and news investigations, he has been front and center in this important fight to protect our pollinators. Read about Mr. Hackenberg, other Forum speakers and how to register, for the Forum at www.beyondpesticides.org/forum
For more information on pollinators and CCD, read our factsheet: Pollinators and Pesticides: Escalating crisis demands action.