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Honey Bee Colony Collapse Disorder

April 25, 2007

There has been a recently reported die-off of bee colonies that has been called serious in some parts of the United States; yet in other areas, beekeepers have not been affected. It has not yet been reported in Illinois, although it has been reported in several midwestern states. This is a threatening situation to beekeepers, as well as those who grow and consume many fruits and vegetables that are primarily pollinated by honey bees. This situation is being called Colony Collapse Disorder (CCD). Similar situations have been labeled in the past as Spring Dwindling, Fall Collapse, Autumn Decline, May Disease, or Disappearing Disease. The term Colony Collapse Disorder is being used instead for a variety of reasons, including that the situation is not necessarily associated with any particular time of the year and that it is not known whether a disease-causing pathogen is involved.

Other than general symptoms, essentially nothing is known about the causative agent. Consequently, everything becomes suspect. Nutrient shortages, viral infections, bacterial infections, genetic paternity conflicts, chemical misuse, high mite populations, digestive diseases, amoeba infestations, immune system failure, and fungal infections are common suggestions for possibly causing the unexplained colony deaths.

One possible cause that is being investigated is the impact of pesticides on honey bees, particularly the insecticide imidacloprid. This insecticide is widely used to control insect pests of fruit, vegetables, turf, and landscape plants. It is sold as Merit, Marathon, Provado, Admire, and Gaucho. There is research indicating that honey bees that contact imidacloprid can lose their memory of where their hive is located. This feature is being used by some to explain why CCD-affected hives have no bees in them—that the bees left to forage and never returned to the hive.

However, even though imidacloprid is systemic and moves through the plant, it is known to not get into the flowers of a number of plants. With bees primarily visiting flowers, there are questions as to how the bees would pick up the imidacloprid. Another question is when the honey bees pick up the imidacloprid. Many imidacloprid-treated crops finish flowering by midsummer, allowing time for seed or fruit to be produced and ripen before frost. Honey bees tend to feed in late summer and fall on late-season flowers such as goldenrod and native asters. These plants tend to be most numerous in noncrop areas where insecticides are unlikely to be applied. If the bees died earlier in the season from visiting flowering crops, beekeepers surely would have noticed this when they collected honey from the hives.

There have been media reports that this new problem may have been ongoing for 3 to 4 years. The numerous general symptoms combined with the broad timeframe become encompassing enough to include nearly any dead colony. It is important that hysteria does not overtake scientific investigation. Apparently, CCD has so far been found in bees that have been recently stressed, that is, bees that have been moved to different locations. The problem is being found primarily with migratory commercial beekeepers. In discussions of CCD characteristics, it is frequently said that hobby beekeepers are not as observant as commercial beekeepers; consequently, their colonies that recently died were simply counted as mite-afflicted or caused by a poor queen. However, many hobby beekeepers are very observant of their hives and would have readily observed symptoms as those exhibited by CCD, especially if it had been going on for several years.

A recent survey (March 14 to 19, 2007) of Ohio beekeepers found that on average there was a 72% loss of live colonies from September 2006 until March 2007. A closer breakout indicated that beekeepers with fewer than 100 colonies had an average 55% loss, those with 100 to 500 colonies averaged 67%, and those with over 500 colonies averaged 75% loss. There did not appear to be any difference by area of the state. Perhaps the reason why the percentage of loss as the size of operation increases is due to the amount of time spent by the beekeeper per colony. At one time, a 10% or less loss was considered normal, but when parasitic mites became common, that number rose to nearly 30%. The 72% is an unheard of amount.

It is difficult to determine what caused the loss of so many colonies. Fall of 2006 in most parts of Ohio had a dearth of nectar, resulting in poor diets for the honey bee colony. In some cases, the queen reduced egg-laying due to the dearth of nectar, resulting in older bees in the colony and a reduced population. Many beekeepers fed their bees, but it may not have been the proper diet. With various medications being used by the beekeeper to control mites and disease within a colony, perhaps these medications are reacting with each other and affecting the bees. As beekeepers breed bees to resist mites, perhaps they are also affecting bee longevity. There are a number of other factors that could also be related, all of which need to be considered when thinking of CCD. In the above-mentioned survey, the two most often cited reasons beekeepers believed to be the cause of their loss were starvation and small clusters. They believed both of those were brought on by the fall of 2006.

A study group called the CCD research group (comprised of university researchers, state and federal regulatory officials, Cooperative Extension educators, and industry representatives) is working to determine if the cause is related to chemicals, management, breeding stock, environmental, bee stress, or some other factor. The CCD group and Bee Alert Technology are requesting that beekeepers fill out the National Bee Loss Survey, which can be found at http://www.beesurvey.com. This survey can be filled out beekeepers with operations of any size, whether or not a loss has been suffered; the more information obtained, the better the chance of finding a cause.

If historical precedents hold true, with the arrival of the spring season, the symptoms will fade into remission. Although the situation is frustrating, no one knows the cause or the scope of this disorder. Don’t panic and do question much of what you hear.
(Phil Nixon; primarily modified from the CCD research group Web site and articles by James E. Tew and John Grafton in the February and March issues of the Ohio Info Bee newsletter.)