The debate over the causes of bees dying around the globe continues as a recent Harvard study points to pesticides and a USDA report suggests mite infestation. The Harvard study conducted by Chensheng Lu compared the impact of neonic pesticide application on 12 hives against six other hives in which the chemical was not applied. Half of the hives receiving the pesticide collapsed and none of the hives without pesticides collapsed. One of the non-pesticide colonies did die off due to a common bee malady nosema, but the bees did not vanish as with the pesticide treated colonies. As to the United States Department of Agriculture (USDA) report, a survey of beekeepers revealed that hives treated for mite infestation fared better in terms of collapse than hives left untreated or treated less vigorously. Instead of one cause, the problem of colony collapse disorder could be derived from several; therefore, the Harvard study and USDA report may not conflict so much as point toward two different causes of colony collapse.
The European Union recently banned the use of neonicotinoids for two years. These pesticides are produced from a variant of nicotine and impact the nervous systems of insects. Some scientists believe that the use of neonic pesticides impedes the ability of bees to find their way back to the hive. If enough bees cannot navigate back to the hive, then the hive collapses. Studying the results of the ban should be helpful in clarifying the continuing debate over the causes of mass bee deaths. Nevertheless, if neonicotinoids are the true culprit, eliminating the problem could take years as the pesticide will still be present in plants and the soil.
One of the producers of neonic pesticides, Bayer, criticized the Harvard study for applying too much pesticide to the applicable hives for too long a period. Bayer noted that the dose administered was 10 times the normal exposure the bees would encounter. Bayer also criticized 13 weeks of exposure as being too long. While these may be valid criticisms of how the study was conducted, the exposure to neonics did kill off half the hives.
As to the USDA report, beekeepers are reporting a reduction in hive losses. Over the past eight years, beekeepers have reported bee losses at over 30 percent. In the most recent reporting period the losses were reduced to 23.2 percent. The USDA says that beekeepers who treat the hives for varroa mites suffer fewer losses than those who do not treat for mites. Further, those who treat four times a year obtain better results than those who treat the hives only once or twice.
While the colony collapse causation debate continues, bees are still dying in droves, just not as many as a few years ago. The European Union ban on three types of neonic pesticides will add more data to study as scientists continue their work to determine the cause of mass bee deaths. The presence of the mites confuses the issue for now. The producers of neonicotinoids will continue to criticize pesticide studies and point to the mites as the cause until more data is available.
By William Costolo