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Pesticide Mixtures have Damaging Affects on Bees

Posted: October 14, 2013

Do combinations of pesticides have varying effects on different species of pollinators? Penn State researchers looked into the typical orchard environment to discover how different insecticides mixed with fungicides affect pollinator species such as honey bees and Japanese orchard bees.
Image: Penn State College of Ag Sciences

Image: Penn State College of Ag Sciences

Do combinations of pesticides have varying effects on different species of pollinators? 

Penn State researchers looked into the typical orchard environment to discover how different insecticides mixed with fungicides affect pollinator species such as honey bees and Japanese orchard bees.Their research was published in PLoS ONE, an online open-access journal for the communication of all peer-reviewed scientific and medical research.

According to Dr. David Biddinger, co-author and associate professor of entomology, many species of bees are important pollinators of tree fruit crops such as apples, pears, plums, cherries and nuts.  “Previous research into pollinator declines focused on detecting pesticide residues, parasites, diseases, and loss of habitat. However, little research has been done on the relative effect of pesticide mixtures that are typically found in orchards, and how these pesticides affect bees other than the honey bee” Biddinger explains.

There are currently registered over 75 pesticides of various classes of chemicals used for management of different pests and disease in orchards. The most critical period to reduce pollinators’ exposure to pesticide application in apple orchards is just prior to, during and just after bloom. This timing is also critical for control of fungal diseases such as apple scab and apple powdery mildew.

During the study, Biddinger and other researchers showed that pesticide effects can can vary between different species of pollinators, and that mixtures of insecticides with fungicides (which are normally thought to be safe to bees) can significantly increase the toxicity of the insecticide to bees. The researchers concluded that because of these varying effects, the pesticide registration process required by the EPA should be modified to include tests on additional species of bees since the honey bee is not representative and should look at common pesticide mixtures.

“Many pesticides are registered as ‘reduced risk’ or ‘organophosophate replacements’ and have toxicity tests with the honey bee, but are in fact toxic to non-targeted organisms, such as other species of pollinators and beneficial predatory and parasitic insects in an integrated pest management program,” says Biddinger.

Biddinger compared their findings to other studies that report detrimental side effects on other bee species despite the fact they passed risk assessments on honey bees. “Considering that the 4,000 species of bees found in the United States may significantly differ in their relative toxicity to pesticides, the EPA needs to review its current policy on testing only the honey bee to determine pollinator safety and include multiple species that are relatively easy to keep in managed colonies.  These include bumble bees, alfalfa leafcutter bees and the as the mason/orchard bees like the Blue Orchard Bee or Japanese Orchard Bees that belong to the genus Osmia. Since many new pesticides have sublethal effects on development, reproduction, or behavior,  adding studies of sublethal effects of these toxicants to bee adults and larvae would also be of great use in determining safety to all bees.

Other authors on the paper “Comparative Toxicities and Synergism of Apple Orchard Pesticides to Apis mellifera (L.) and Osmia cornifrons (Radoszkowski)” are Jacqueline L. Robertson, USDA Forest Service PSW Station; Chris Mullin, James Frazier, Sara A. Ashcraft, Edwin G. Rajotte, Neelendra K. Joshi, Department of Entomology, Pennsylvania State University; and Mace Vaughn, The Xerces Society.

For more information on pollinator research, visit The Penn State Center for Pollinator Research web site at http://ento.psu.edu/pollinators. The center, which is devoted to the study of pollination, pollinators and pollinator management and protection, comprises 26 independent faculty, including researchers, educators, extension specialists and outreach coordinators, spanning multiple departments and colleges at Penn State.