The following is a summary of:
Pettis JS, Lichtenberg EM, Andree M, Stitzinger J, Rose R, et al. (2013) Crop Pollination Exposes Honey Bees to Pesticides Which Alters Their Susceptibility to the Gut Pathogen Nosema ceranae. PLoS ONE 8(7): e70182. doi:10.1371/journal.pone.0070182
A study published by the University of Maryland and the US Department of Agriculture in late July offers tantalizing evidence of the cause of Colony Collapse Disorder.
Researchers in the study gathered pollen from honey bee hives throughout the East Coast from Delaware to Maine. They analyzed the samples to determine if the pollen contained pesticides. They found that on average each sample contained 9 different agricultural chemicals. All pesticide levels were sublethal, and the two most common chemicals found were a fungicide, chlorothalonil, and an insecticide, fluvalinate, used by beekeepers to control Varroa mites. Varroa mites are a common honeybee pest, and I will write another entry on them soon.
Researchers then fed health honeybees the contaminated pollen samples. They found that the honeybees lost their ability to fight off Nosema, a fungus that also affects honey bees, when they were fed the samples containing chlorthalonil. The results were surprising, and research Dennis vanEngelsdorp noted:
“We don’t think of fungicides as having a negative effect on bees, because they’re not designed to kill insects, Federal regulations restrict the use of insecticides while pollinating insects are foraging, he said, “but there are no such restrictions on fungicides, so you’ll often see fungicide applications going on while bees are foraging on the crop. This finding suggests that we have to reconsider that policy.”
The more I read on the topic, the more I am forced to conclude that there is not one smoking gun causing colony collapse disorder. I think there are probably a number of factors interacting to cause the colony collapses we have seen over the past decade. And, while this study is not direct evidence on the cause of colony collapse disorder, it does offer an explanation for at least one of the factors that is causing stress on the honey bee populations.
See here for the original study published online.
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0070182
BEE AWARE 