The story of the tracheal mite’s impact on honey bees is full of contradiction and confusion. Those examining the effects on bee populations of future plagues and pests would do well to study the history of this controversial parasite.
Great losses of bee colonies on the Isle of Wight in the British Isles during the years 1901-1905 were correlated with the eventual discovery of Acarapis woodi by Dr. J. Rennie in 1919. This prompted a furor which to continues to this day. Leslie Bailey a renowned authority on bee diseases1 has written extensively on the mite. He called the “Isle of Wight Disease,” presumably caused by the tracheal mite, a myth.2
Dr. Bailey says a primary reason for the notoriety of “Isle of Wight Disease” was sensationalized press releases which caught beekeepers’ attention. His observations on the issue include:
1. Major symptoms described, such as bees with distended abdomens or that cannot fly “crawlers,” are indicative of many kinds of diseases, including Nosema. Prior to discovery of the mite, Nosema was in fact diagnosed as the problem. Crawlers were often not as infested with mites as were normal individuals.
2. The disease correlated with a time of disastrous winter weather; there were at the same time no losses in other beekeeping areas from mites.
3. The assumption that all parasites cause “serious damage” is not valid. Although tracheal mites shorten infested bees lives, according to Dr. Bailey, it is only by a “relative amount.”
Dr. Bailey’s conclusion was that the mite was a scapegoat for large colony losses. He also stated that beekeepers did not understand the disastrous effects of their own actions including experimental treatments, moving bees and especially transferring bees from skeps to moveable-frame hives. Finally, he said that beekeepers were not aware of all possibilities and were searching for specific answers to a complex problem. This parallels to a great extent some of the continuing controversy over another more recent condition called “colony collapse disorder.”
There is another side to the tracheal mite issue. Brother Adam, a monk at Buckfast Abbey, contradicts Dr. Bailey’s ideas on “Isle of Wight Disease.”3 He concluded that it was a new disease and the spread was very rapid since many incidences were reported on the British Isles when infested bees were moved in. Weather factors were not contributive; honey flows were better than average; nor were beekeeping practices at fault. With reference to the latter, Brother Adam says, a transition period from skeps to moveable-frame hives did occur, but beekeepers did not lack skills nor experience.
In addition, symptoms of Nosema disease, Brother Adam said, were different than those found in “Isle of Wight disease.” They were more like “disappearing disease” and the queen was usually not affected, which is the case in Nosema.
Brother Adam’s answer to tracheal mites was breeding resistant bees. He says the mites reached his Abbey in 1915, when crawling bees were seen and even though all colonies produced excellent spring clove(r and heather crops, some 30 died that winter. Only Italian bees (Apis mellifera ligustica) survived; all British bees (Apis mellifera mellifera) died. This may be the reason that most honey bees currently in the U.S. are Italian; they presumably were considered tolerant to many traditional bee diseases, including tracheal mites. Efforts in breeding tracheal mite-resistant/tolerant bees at the Abbey continued until Brother Adam’s death. At least one strain of so-called “Buckfast Bee” is now available commercially in the United States, but the actual effectiveness of breeding this bhoney bee is an open question. Those purchasing this brand of bee should ask the producer to provide specific data backing up any advertising claims as noted by Contributor Dave Cushman.
The tracheal mite Acarapis woodi was detected in the United States in 1984. Principle points of introduction appeared to be in the southern U.S (Texas and Florida). At first honey bee colonies were destroyed by Animal PLant Health Inspection Service (APHIS) in an effort to control the mites, however, this policy was soon abandoned. Whether or not tracheal mites were a “problem” for beekeepers took on many of the same dimensions as described above for “Isle of Wight Disease.” In some areas, the mite was declared to be responsible for many colony deaths; in others, there appeared to be no impact.
It is not yet known exactly how the tracheal mite actually affects a honey bee colony, remaining an enigma. Losses appear to be worse in areas where winters are severe. There were a good many colony deaths in the first few years in the U.S., however, many areas have recovered. Menthol, a natural product, is now labelled for treatment of mites, but requires specific environmental conditions to be fully effective.
The tracheal mite’s life cycle is not fully understood nor are its population dynamics in a bee colony known. There are no recommended mite thresholds. Research on tracheal mites is confounded by a lack of statistically valid sampling procedures and the problem that detection requires a great deal of time-consuming labor in dissections. Finally, it is almost impossible to isolate the effects of tracheal mites on a colony, especially when other ailments (foulbrood, chalkbrood, nosema) might also be present.
Most recently it appears that tracheal mites have taken a back seat to many other problems that currently affect beekeepers. In Mexico, and possibly Clifornia and Florida, there is evidence that tracheal-mite-resistant honey bees might have spontaneously developed in the face of great losses with little subsequent treatments.
1 See the classic volume, L. Bailey, Honey Bee Pathology, London: Academic Press, 1981.
2 L. Bailey, “The ‘Isle of Wight Disease’: The Origin and Significance of the Myth,” Bee World, Vol. 45, pp. 32-37, 1964.
3 B. Adam, “‘Isle of Wight’ or Acarine Disease: Its Historical and Practical Aspects,” Bee World, Vol. 49, pp. 6-18, 1968.