Bee Die-Offs Linked to Pesticide Mixtures, Window of Exposure

(Beyond Pesticides, November 3, 2009) Research by scientists at the University of Florida (UF) links Colony Collapse Disorder (CCD), the widespread disappearance of honey bees that has killed off more than a third of commercial honey bees in the U.S., to larval exposure to a cocktail of frequently used pesticides. Led by UF Institute of Food and Agricultural Sciences bee specialist Jamie Ellis, PhD, the researchers have finished a first round of testing on bee larvae exposed to the pesticides most commonly found in bee hives. The results were presented on October 22 at a meeting of the North American Pollinator Protection Campaign (NAPPC), which funded the study.

The work gives insight into how the larvae react to these pesticides, which are usually only tested on adult bees, and sets the stage for the researchers to test the bees’ reaction to combinations of these pesticides. Just like mixing the wrong medications can have deadly and unpredictable results in humans, chemical mixtures pose a quandary for the bee industry. Bees are commonly exposed to multiple pesticides that are either applied to or nearby their hives.

“Beeswax, honey and pollen can contain low mixtures of fungicides, insecticides, and herbicides. The larvae develop in the presence of and consume these mixtures,” Dr. Ellis said. “Any one of these pesticides may not be that harmful to the developing larvae. However, it is possible that combinations of the pesticides can interact.”

The work is among the first to look at such combinations of chemicals introduced at the larval stage. The study examines the individual effects of herbicides, fungicides and insecticides commonly found in bee hives (chlorothalonil, mycobutanil, simazine, glyphosate, chlorpyrifos, coumaphos, fluvanlinate, imidacloprid and amitraz). To study these pesticides, the researchers transferred individual larvae to special containers where they were given a typical diet containing a dose of the pesticide.

Some of the pesticides yielded surprising results. For example, the bees seemed to show an erratic response to coumaphos and fluvalinate, which are commonly used to kill hive-infecting Varroa mites. This could mean that some bees have become resistant to the pesticide while others have not, said Mike Scharf, PhD, a UF entomologist and co-primary investigator on the project.

“There’s a really complex and unpredictable interaction of chemicals and genetics at play,” Dr. Scharf said. Even more so, he added, when the bees are exposed at the larval stage. Pesticide exposure at this developmental stage could have significant effects on the adult bees.

Later research will reintroduce these adult bees into the hive to see how the pesticide-exposed bees react to common stressors, such as Varroa mites and bacterial infections.

“It is going to be a lot of work to run through all these scenarios, but at the end of the day, it’s the only way to really find out how all these factors come together,” Dr. Ellis said. “It’s worth the work. Bees are a fundamental part of our ecosystem and our food chain.”

Dr. Ellis says the research will be submitted for publication by the end of the year.

Research is ongoing as to the cause of the CCD phenomenon, but pesticides, especially neonictinoids, such as imidacloprid, 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. For more information on pollinators and CCD, read our factsheet: Pollinators and Pesticides: Escalating crisis demands action.

Beyond Pesticides believes that pesticides are likely to be a part of the CCD equation and a precautionary approach must be taken. Solutions to the loss of bees and human productivity are clearly within our reach if we engage our communities and governmental bodies. We know how to live in harmony with the ecosystem through the adoption of sustainable practices that simply do not allow toxic pesticide use. Because our survival depends on healthy pollinators, we must do everything in our power to solve this problem.

Read other Daily News Blog postings on pollinators and pesticides.

Take Action: Email EPA Administrator Lisa Jackson and tell EPA to take a precautionary approach regarding pesticides that kill or have sublethal impacts on bees and other pollinators.