APIS Volume 9, Number 6, June 1991
In this issue
- Tracheal Mite Enigma
- Disease Diagnosis Booklet
- National Honey Board Referendum Vote
TRACHEAL MITE ENIGMA
There are a good many beekeepers and scientists scratching their heads about tracheal mites. Nobody seems to be able to reconcile why high mite levels last fall did not necessarily translate into large colony losses this spring. Informal reports from California to Michigan reveal this quandary. Dr. Roger Hoopingarner in his last B-Plus, the beekeeping report from Michigan State University, summed it up:
"I still have not figured out the tracheal mite...A year ago one of the colonies that survived the winter was headed by a daughter queen from the Lonesome Hive (a colony Dr. Hoopingarner keeps in his yard). It had a tracheal mite level of about 80% at that time. It still has the same queen this year, and yet the tracheal mite levels have dropped from 33 to 45% in the two samples that we have examined this winter. At the inspection yesterday (April 18, 1991), I had to divide the colony since it had five hive bodies (3/4 depth supers) full of bees. They were starting queen cells!"
Other pieces of evidence add to the confusion. It seems that researchers in the Rio Grande Valley of Texas, where the first detection of Acarapis woodi occurred in 1984, are unable to keep mite levels high enough to do effective research on the critter. Early studies in Florida were also plagued with very large variation in mite populations that confounded investigators. Some California beekeepers had high mite levels in their colonies last fall and were expecting the worst, but in contrast to previous years' experience, most hives came through the winter with flying colors. Beekeepers in Florida's panhandle have not experienced losses similar to those in 1986-1988, which many attributed to tracheal mites. Some colonies in Florida have traditionally had high mite infestations, but never suffered the devastation visited on those in the panhandle.
All this is not surprising considering the tracheal mite literature and its subsequent introduction into the United States. It may be instructive, therefore, to review 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 the Tracheal mite, Acarapis woodi, by Dr. J. Rennie in 1919. Dr. Leslie Bailey, a renowned authority on bee diseases, called the "Isle of Wight Disease," presumably caused by the tracheal mite, a myth (L. Bailey, "The 'Isle of Wight Disease': The Origin and Significance of the Myth," Bee World, Vol. 45, pp. 32-37, 1964). Dr. Bailey said 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:
- Major symptoms described, such as bees with distended abdomens or 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.
- The disease correlated with a time of disastrous winter weather; there were at the same time no losses in other beekeeping areas from mites.
- 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. After detection in the United States, Dr. Bailey stuck to his guns and predicted the mite would not be a problem here.
There is another side to the tracheal mite issue. Brother Adam, a monk at Buckfast Abbey, disagreed with Dr. Bailey's ideas on "Isle of Wight Disease." (B. Adam, "'Isle of Wight' or Acarine Disease: Its Historical and Practical Aspects," Bee World, Vol. 49, pp. 6-18, 1968). 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 said, a transition period from skeps to moveable-frame hives did occur, but beekeepers did not lack skills or 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.
When the tracheal mite (Acarapis woodi) was first detected in the United States, several hundred 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." Six years after its introduction, the arguments continue.
This brings us back to Brother Adam. His answer to tracheal mites has been breeding resistant bees. He reported the mites reached Buckfast Abbey in 1915, when crawling bees were seen and even though all colonies produced excellent spring clover and heather crops, some 30 died that winter. Only Italian bees survived; all British bees died. The surviving stock became the nucleus of the Abbey's breeding program.
A recent article in the Wall Street Journal touts Brother Adam's work in developing resistant bees, calling his Buckfast queen, the "Breakthrough Bee Bred by a British Monk." According to the article, the U.S. Department of Agriculture brought in 15 Buckfast queens; one died enroute, but the remaining 14 survived a six-month quarantine on a Louisiana island. They are now being propagated on a large scale; it is hoped the descendants will produce disease resistant colonies in areas of the U.S.
As Brother Adam concludes, according to the article,"Americans have always taken the health of their bees for granted. Now they must pull up their socks--or lose their colonies." Presumably this means using his "disease resistant" stock. Unfortunately, the tenor of the article is more journalistic jargon than anything else. There is no mention of controversy surrounding either introduction of the stock itself or the methods used by Brother Adam to determine resistance. Nor is his long-standing debate with Dr. Bailey referred to. The fact remains that, like many beekeeping issues, the tracheal mite story is too long to fit in a prescribed number of column inches in any newspaper.
Several major gaps in our knowledge lead one to be skeptical about experiments with and claims for tracheal mite resistance. The mite's life cycle is not fully understood; nor is its population dynamics in a bee colony. There are no recommended mite thresholds above which it is suggested to treat colonies. The one material currently registered for treatment is tricky to apply and thus, its reliability is always in question. Research on tracheal mites is confounded by a lack of statistically valid sampling procedures and the problem that detection is destructive of bees and the required dissections are extremely labor intensive. Perhaps the biggest unknown is how the tracheal mite actually damages a bee colony. According to the article mentioned above, mites "...clog the breathing tubes of bees,...leaving millions of honey bees gasping for breath." This scenario is possible considering the packed condition of many heavily infested tracheae. However, holes are also punctured through the tracheae and hemolymph is probably sucked up by mites. Secondary infections of fungus or virus are always possible. 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. Until much of the above information is known, the tracheal mite enigma will continue.
The tracheal mite situation parallels many disease and pest situations in beekeeping which appear to ebb and flow through the years. For example, I now have reports of an extreme chalkbrood epidemic in Israel and the Brazilian-Argentinean border continues to be affected with an outbreak of American foulbrood. It seems that beekeepers are not immune from situations that plague other agriculturalists. Prevailing environmental conditions will favor certain disease or pest problems each year in ways that are often not predictable. It's the kind of thing that causes beekeepers, and in spite of Brother Adam's protests to the contrary as reported in the Wall Street Journal, bee scientists, to have sleepless nights.
DISEASE DIAGNOSIS
A new booklet has just been published by the USDA's Agricultural Research Service. It is Agriculture Handbook 690, written by Drs. H. Shimanuki and D. Knox and entitled: Diagnosis of Honey Bee Diseases. The purpose of the publication is to acquaint readers with laboratory techniques used to diagnose diseases and detect and identify parasites, pests, and other abnormalities of the honey bee.
The handbook accomplishes its objective very well. Several methods of detection for brood diseases are described and accompanied with helpful line drawing. A table of comparative symptoms for American and European foulbrood, sacbrood and chalkbrood is also included. Adult diseases pests, parasites and predators are also described in some detail in the publication. Nine methods are shown to detect tracheal mites. Diagnosis of both Varroa jacobsoni and Tropilaelaps clareae are detailed. Finally, there is a section on Africanized honey bees and pesticide poisoning.
Although the information is excellent in the 57-page booklet, getting a copy looks to be a potential headache. Inside the cover it states that copies are available from the National Technical Information Service, 5285 Port Royal Rd., Springfield, VA 22161. However, phone calls (703/321-85470) to the service have resulted in the agency not being able to find the publication. A problem appears to be that the handbook is so new (April, 1991) that it is not yet in the system. Maybe by the time this newsletter gets to you, the publication will be ready for sale to the public.
NATIONAL HONEY BOARD REFERENDUM
The long-awaited referendum on the Research, Promotion and Consumer Information Order for honey will be held this August, according to the U.S. Department of Agriculture's Agricultural Marketing Service. The referendum period will be August 1 through August 31, 1991. All ballots must be postmarked by August 31 and received by September 6. Two questions will be on the ballot: Question No. 1: Do you favor a continuation of the Research, Promotion and Consumer Information Order for Honey?
A "YES" vote on question No. 1 means you are in favor of the continuation of the order. A "NO" votes means you are opposed to its continuation.
Question No. 2: Do you favor termination of the refund of assessment provisions of the Research, Promotion and Consumer Information Order for Honey?
A "YES" vote on question No. 2 means you are in favor of the termination of the refund provision. A "NO" vote means you are opposed to the termination of the refund of assessments.
Both questions will be tabulated independently. Voters should respond to both questions. Questions left unanswered will not be counted. Eligibility to vote is limited to any person who produced or imported honey into the U.S. duirng the period January 1, 1990 through December 31,1990 and who is now a producer or importer of honey. For further information on eligibility, contact your local ASCS Office.
Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (904) 392-1801, Ext. 143 FAX: 904-392-0190
INTERNET Address:MTS@GNV.IFAS.UFL.EDU
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