APIS Volume 6, Number 2, February 1988
In this issue
- Inexplained Bee Kills Again: Varroa or Virus
UNEXPLAINED BEE KILLS AGAIN
There are reports again this year of widespread colony dieoff in the panhandle. The symptoms appear to be very similar to those reported last year where colonies went into winter in good shape, but dwindled to a handfull by February, in spite of large amounts of surplus food (both honey and pollen) on the colony. The previous kill was thought by many to be the result of drought induced pollen shortage. Others attributed it to a combination of several potential reasons including tracheal mites, amoeba disease, nosema, bacterial or viral infection.
Subsequent to my writings on the subject last year (February, March and April 1987 APIS), I received a good deal of correspondence on the subject, most of it in agreement that pollen shortage was indeed the culprit. Of particular interest, was a letter from Dr. Jovan Kulincevic (formerly at the Ohio State University) who now works for Pcelarski Kombinat in Belgrade, Yugoslavia. He compared the losses I reported to experiences in his country where some 50% to 80% of colonies died over a widespread area:
"We think the main cause for such bee kill in Varroa jacobsoni, but more than that the acute paralysis virus which is transferred and activated by Varroa. There are also other factors such as nosema and a very long winter, and also the problem of pollen could be taken into consideration. Anyhow it seems that the virus infection played a main role in the dieoff. According to Bailey this virus normally does not cause a disease in bees, but if Varroa transfers it from hemolymph or one bee and injects it into another, then fast replication of the virus happens and bees quickly die. Could Acrapis woodi (tracheal mite) in your case have a similar role as Varroa has here?"
The vast majority of samples sent to the Beneficial Insects Laboratory in Beltsville, Maryland to date in an effort to discover what is behind this latest dieoff do have heavy infestations of tracheal mite. Does this mean then that other reasons cannot be ruled out? The answer is no. In an effort to obtain more information on the situation, the Division of Plant Industry, Apiary Bureau in cooperation with the University of Florida (IFAS) is investigating the possibility of placing an experimental apiary in the panhandle area.
In the meantime, beekeepers are urged to bear in mind the words of Dr. L. Bailey in his classic book, Honey Bee Pathology:
"A wide variety of specific pathogens are endemic in honey bees, and most of them are perpetuated as inapparent infections. Colonies, and even individual insects, that are infected with certain, sometimes several, pathogens frequently seem outwardly normal of an indefinite period. Accordingly, it is often difficult to identify the causes of losses and disorders, and this has led to much confusion and many false diagnoses; especially when some pathogens, particularly viruses, have gone unrecognized.""The available evidence shows that honey bee pathogens multiply and spread to cause more damage than usual within those colonies that are most hindered in their development by adverse environmental events. Food shortage is the first result of these unfavourable conditions for bees in nature, and is often associated with an abnormal increase in pathogens. This is analogous to the nature of infectious diseases in other wild animal communities, in which severe disease is generally associated with food shortage and is a secondary cause of death."
Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (352) 392-1801, Ext. 143 FAX: (352)-392-0190
http://www.ifas.ufl.edu/~mts/apishtm/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1988 M.T. Sanford "All Rights Reserved
