Study sheds light on bee decline threatening crops
A study by researchers at the University of Toronto suggests that a disease is being spread to wild bumble bees from commercially reared bumble bees used to pollinate greenhouse crops, and this could be a factor in declining populations.
It concluded that improved management of domestic bees, for example by reducing their parasite loads and their contact with wild bees, could diminish or even eliminate the spread of disease.
The research, published in the Public Library of Science journal PLoS ONE, said: “The conservation of insect pollinators is drawing attention because of reported declines in bee species and the ‘ecosystem services’ they provide. This issue has been brought to a head by recent devastating losses of honey bees throughout North America, so called Colony Collapse Disorder (CCD), yet we still have little understanding of the cause(s) of bee declines.
“Wild bumble bees have also suffered serious declines and circumstantial evidence suggests that pathogen ‘spillover’ from commercially reared bumble bees, which are used extensively to pollinate greenhouse crops, is a possible cause.”
In North America, greenhouses have used commercial bumble bees extensively for the pollination of tomato and bell pepper. Generally, bee pollination is valued at $15b annually to US agriculture and honey bees are responsible for pollinating more than 130 different crops.
For the last few winters, more than 25 per cent of the US honey bee population has vanished, with early reports from beekeepers indicating this phenomenon was continuing in 2008.
The various reasons for the decline in bees include poor nutrition, invasive mites and CCD, where bees from a colony desert the hive and die.
Colony collapse
The US Department of Agriculture has a long-term action plan to address the problems affecting honeybees and last month it announced $4m in funding to the University of Georgia to study the causes of CCD and other problems affecting bee populations.
Meanwhile the food industry is also taking action. In February The Häagen-Dazs loves Honey Bees campaign was launched to raise research funds and awareness about the plight of the bees.
A Häagen-Dazs spokesperson told FoodNavigator-USA.com: “More than 40 percent of Häagen-Dazs ice cream flavors are dependent on honey bee pollination, but honey is not a major ingredient in all of our ice cream.
“Ingredients like almonds and berries are foods that are bee-dependent, and since Häagen-Dazs ice cream is dedicated to remaining an all-natural brand, if we find some of these items difficult to source we’ll eventually have to reexamine our flavor line.”
Other food companies have also warned of potential crises if crops are not correctly pollinated.
And there is a honey shortage, according to the Sue Bee Honey cooperative marketing organization which said that in the last year the US crop was about 150 million pounds, compared to the average of 200 million pounds.
Research results
The research into bumble bees said that the CCD “epidemic” which destroyed 50–90 percent of colonies in affected honey bee operations in the last year appears to be the result of a contagious pathogen. Wild bumble bees are also suffering serious declines throughout North America and the UK and the authors looked how disease has spread among them.
They created a model of the pathogen spillover (disease spread) and looked at a destructive pathogen called Crithidia bombi seen in commercial bumble bees. They also monitored bumble bee populations in the wild near greenhouses for evidence of the pathogen spreading.
They found that the pattern of infection in the wild was consistent with the model, which predicted that “during the first three months of spillover, transmission from commercial hives would infect up to 20 percent of wild bumble bees within two km of the greenhouse”.
However, it added that a travelling wave of disease is predicted to form suddenly, infecting up to 35–100 percent of wild bumble bees and spread away from the greenhouse at a rate of two km per week.
Source: PLoS ONE 3(7): e2771. doi:10.1371/journal.pone.0002771
“Does Pathogen Spillover from Commercially Reared Bumble Bees Threaten Wild Pollinators?”
Authors: Michael C Otterstatter, James D Thomson
