By Lisa M. Campbell and James V. Aidala
Recently, the results of a three-year University of Maryland study assessing the potential chronic sublethal effects on whole honey bee colonies of a diet containing imidacloprid, an insecticide that belongs to the neonicotinoid class of chemicals, at 5, 20, and 100 μg/kg over multiple brood cycles have been released. The study, Assessment of Chronic Sublethal Effects of Imidacloprid on Honey Bee Colony Health, funded primarily by a Cooperative Agreement with the U.S. Department of Agriculture (USDA) Agricultural Research Service (ARS) Bee Research Laboratory, concludes that: “chronic exposure to imidacloprid at the higher range of field doses…could cause negative impacts on honey bee colony health and reduced overwintering success, but the most likely encountered high range of field doses relevant for seed-treated crops (5 μg/kg) had negligible effects on colony health and are unlikely a sole cause of colony declines.”
This study examines a number of recent controversial issues behind the bee health discussion, including: whether pesticides have an impact when one examines exposure levels approximating actual field condition exposure levels and whether the pesticide use has a substantial impact on hive and hive survival (and not just an impact on individual bees). The study results will likely be used by others to help evaluate the meaning of many of the studies various researchers have conducted over the past three to five years that are often cited in the media. Critics of these other studies have noted the “excessive” amounts of the pesticides used in the research protocol. They have also noted that, as insecticides, the neonicotinoid products are designed to kill insects, and since bees are insects, some bee mortality can be expected if exposed to the material. The University of Maryland study sought to emulate more realistic field conditions in the study protocol. Its conclusion, that there were “negligible effects on colony health” over a three-year period, is significant.
Also fairly recently, the Congressional Research Service (CRS) issued a report on bee health and pesticides, Bee Health: the Role of Pesticides. The report states that although the report focuses on bee exposure to pesticides, this does not imply that pesticides have a higher influence on the health and wellness of bees than other identified factors. The report states: “Although pesticides have been shown to damage bee health, it is unclear whether the level of harm is sufficient to attribute pesticides as the single or as the major cause of honey bee population declines.” The report further states that there is “the possibility that bees are being negatively affected by cumulative, multiple exposures and/or the interactive effects of several of these factors.” The CRS report refers to conclusions outlined in the USDA and the U.S. Environmental Protection Agency’s (EPA) joint Report on the National Stakeholders Conference on Honey Bee Health, including that “no research conclusively points to one single cause for the large number of honey bee deaths.”
The report details several actions the federal government is taking to promote the health of honey bees and other pollinators:
* The establishment of a Pollinator Health Task Force co-chaired by USDA and EPA that will “focus federal efforts on understanding, preventing, and recovering from pollinator losses.”
* EPA’s pesticide registration review of all neonicotinoid insecticides, and EPA’s development of new pesticide labels that prohibit use of some neonicotinoid pesticide products where bees are present, including products containing imidacloprid, dinotefuran, clothianidin, thiamethoxam, tolfenpyrad, and cyantraniliprole.
* The U.S. Fish and Wildlife Service (FWS) will be phasing out the use of neonicotinoid pesticides in all of its wildlife refuges as well as the feeding of genetically engineered crops to wildlife by January 2016.