By KEVIN WALKER
COLLEGE PARK, Md. — Another study, published in the PlosOne online scientific journal late last month, may be another piece in the scientific puzzle that is colony collapse disorder (CCD).
CCD is the phenomenon in which honeybees disappear from the hive for no apparent reason, never to return. At first, scientists looked for one cause for the phenomenon, but as time went by they seemed to settle on a multi-causal theory of the bees’ mysterious behavior. “Scientists have gotten too excited too many times” about one possible cause of CCD, said Mike Hansen, Michigan state apiarist.
The study, published in the July issue of PlosOne, found that fungicides may play a bigger role in bee health and CCD than was previously thought. “I think there is consensus that the problem is multivariate – so, it’s several things coming together,” said Dennis vanEngelsdorp last week. He is a co-author of the latest study.
“Different things at different times, so that’s informative – think about cancer or heart disease – I think we have made advancements in those fields, but that doesn’t mean we have nailed down a solution.
“The problem is complex, as is the solution.”
This latest study found a pollen sample’s fungicide load significantly affected the bee disease Nosema’s prevalence, among bees fed that pollen. This is something new, as it was previously thought fungicides were among the safer products to be used around bees.
“The combination of high pesticide loads and increased Nosema infection rates in bees that consumed greater quantities of the fungicides chlorothalonil and pyraclostrobin suggest that some fungicides have stronger impacts on bee health than previously thought,” it states. “Nosema infection was more than twice as likely in bees that consumed these fungicides than in bees that did not.”
The authors note there is a need for more research into the “synergistic effects” among different pesticides found around bees as well as the relationship between pesticides and bee diseases. “Fungicides quite possibly play a role in affecting the mid-gut of the bee and might interact with Nosema,” Hansen said. “It’s like you and me – when we go through chemotherapy or something similar, it can affect the bacteria in your stomach. If you’re compromised and can’t take in food properly, then it affects your ability to fight disease.”
Could this be what’s causing CCD? Hansen said something else has happened with bee diseases in recent years. In North America, it used to be that Nosema apis was the more common disease; now, though, it’s Nosema ceranae.
“This change has been coming for quite some time, but recently it’s flipped over completely,” he explained.
Hansen noted in Canada beekeepers either wrap their bees for the winter or keep them inside heated buildings, so they can’t fly away. He said they are finding varroa mites or microsporidian, a kind of fungus, when the colony has died. In the United States there are 28 significant bee viruses. The most significant are deformed wing virus (DWV) and black queen cell virus. “They are a participating factor in the losses,” he said. “The fungicide thing is just part of this whole package of CCD.”
Meanwhile, just last week the U.S. Environmental Protection Agency (EPA) announced it had developed new pesticide labels that will prohibit the use of some neonicotinoid pesticide products where bees are present. This, despite the fact few studies have shown any connection between neonicotinoids and CCD.
“Multiple factors play a role in bee colony declines, including pesticides,” said Jim Jones, assistant administrator for the Office of Chemical Safety and Pollution Prevention at the EPA. The new labels will affect products containing the neonicotinoids imidacloprid, dinotefuran, clothianidin and thiamethoxam.