Bee collapse still not understood

Bee collapse still not understood

Despite years of research, scientists still do not know cause of honeybee die-offs.

HONEYBEES should be on everyone's worry list, but not because of the risk of getting stung, an expert on the bee health said at the 246th national meeting and exposition of the American Chemical Society (ACS).

Dr. Richard Fell, a professor emeritus of entomology at Virginia Tech, said despite years of intensive research, scientists do not understand the cause, nor can they provide remedies, for what is killing honeybees.

Farmers use honeybees to pollinate more than 100 different fruit and vegetable crops around the country in an approach known as "managed pollination." It involves placing beehives in fields when crops are ready for pollination.

"Some estimates put the value of honeybees in pollinating fruit, vegetable and other crops at almost $15 billion annually," Fell said. "Without bees to spread pollen from the male parts of plants to the female parts, fruit may not form. That would severely impact consumers, affecting the price of some of the healthiest and most desirable foods."

Fell discussed the ongoing decline in honeybee populations in the U.S. and some other countries — a condition sometimes termed colony collapse disorder (CCD). Although honeybees have been doing better in recent years, something continues to kill about one in every three honeybees each year.

"The biggest impacts from decreased hive numbers will be felt by farmers producing crops with high pollination requirements, such as almonds. Consumers may see a lowered availability of certain fruits and vegetables and some higher costs," explained Fell, an authority on colony decline in bees.

Some of the leading theories about the cause of CCD include the use of certain pesticides, parasites, diseases and overall hive nutrition.

"There is a good bit of misinformation in the popular press about CCD and colony decline, especially with regard to pesticides," Fell said. "I think it is important to emphasize that we do not understand the causes of colony decline and CCD and that there are probably a number of factors involved. Also, the factors that trigger a decline may be different in different areas of the country and at different times of year."

Beekeeper and other organizations are pushing to stop the sale of certain neonicotinoids — insecticides that some regard as the main culprit of CCD. However, Fell said that move would be premature.

The U.S. Environmental Protection Agency recently reviewed the situation and concluded that there is no scientific evidence that neonicotinoids are causing serious problems with bee colonies.

Honeybees are not the only species of bee that can be used in managed pollination. If colonies continue declining, Fell believes that there will be an increase in the use of other species, including the bumblebee and alfalfa leafcutter bee. There are, however, measured declines in these species' populations as well. In addition, they are not as easily managed for pollination as the honeybee.

"The major advantages of using honeybees are ease of movement both in and out of orchards or fields, as well as the ability to manage colonies for higher populations. Honeybee colonies can be moved from one crop to another in a single season — something that cannot be done easily with bumblebees or solitary bee species such as the alfalfa leafcutter bee," Fell explained. "If we can gain a better understanding of the factors causing honeybee decline, we may be able to apply this knowledge to protecting other species."


Bee disease studied

In other bee-related news, scientists at the University of Warwick in the U.K. have modeled an outbreak of the bee infection American foulbrood using a technique that they say could be applied to other honeybee diseases such as European foulbrood and the varroa parasite.

As well as modeling how bee infections spread, the method also allows scientists to simulate various disease control interventions in order to measure their efficacy.

American foulbrood is caused by the bacterium Paenibacillus larvae, which affects the larval stage of honeybees. It can cause the death of an entire hive within a matter of months.

The researchers used two sets of data gathered two months apart during an outbreak of American foulbrood in New Jersey in the summer of 2010. This provided two "snapshots" of the disease from which they attempted to reconstruct the entire epidemic.

Reconstructions like this are common for livestock infections, but this is the first time the method has been applied to bee disease, the university explained.

The New Jersey data covered 450 honeybee hives, their location and their owners, from which the researchers built a computer simulation to model the speed at which the infection grew as well as how it spread geographically.

Dr. Samik Datta of the WIDER group, based at the University of Warwick School of Life Sciences

, said, "American foulbrood is an unusually virulent disease that can wipe out a hive within a few months. By understanding how it spreads from hive to hive, we then have a good basis to formulate interventions.

"This is the first rigorous statistical analysis carried out on a honeybee disease epidemic that we are aware of," Datta added.

The model suggested that just under half of the 2010 infection's spread was attributed to transmission by owners between their own hives. The distance between colonies was another important factor in the spread of the disease, which mostly spread between hives fewer than 2 km apart.

The model also simulated the impact of different strategies on controlling the epidemic and found that the measures taken by authorities in New Jersey at the time — to inspect and destroy infected colonies — were the most effective.

However, the model suggested that an earlier intervention would have made disease extinction more likely.

The researchers now hope to expand their model to investigate the spread of European foulbrood.

"Using just two snapshots of data, we have been able to reconstruct this epidemic, and we are confident that our technique can be applied to a wide range of other outbreak scenarios," Datta said.

The research was published in the Journal of the Royal Society Interface.

Volume:85 Issue:39

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