APIS Volume 10, Number 4, April 1992
In this issue:
- Registration of Beekeepers Becomes Law
- Lyme Disease Update
- Varroa Damage and Monitoring
- Fluvalinate Pros and Cons
REGISTRATION LAW PASSES
It is now official. Effective July 1, 1992, Florida's Beekeeper Registration Fee will go into effect. The bill implementing the fee was passed by the legislature and the Division of Plant Industry, Florida Department of Agriculture and Consumer Services is now setting up a proposed fee structure. For current information, contact Mr. Laurence Cutts, Chief Apiary Inspector, Division of Plant Industry, P.O. Box 147100, Gainesville, FL 32614-7100, ph 904/372-3505, ext. 128. For more on bee inspection, see the August 1991 APIS.
LYME DISEASE UPDATE
According to the newsletter of the Florida Mosquito Control Association (Buzz Words, April, 1992), there were 9344 cases of Lyme disease reported in 1991 versus 7943 in 1990. In Florida, the number of diagnoses went from seven in 1990 to 35 in 1991. However, the Communicable Disease Center in Atlanta does not consider the disease endemic in Florida and it is not yet a reportable disease in the state. Lyme disease continues to be poorly understood and little research on potential vectors is being conducted.
As the active tick season approaches in Florida, beekeepers should keep in mind that the disease is tick borne and know its symptoms. The February, 1992 issue of APIS contains detailed information on Lyme disease.
VARROA DAMAGE AND MONITORING
The rest of the United States is starting to realize what many beekeepers in Florida have learned in the last two years. Varroa mites are here to stay and monitoring the mite population is the best way to keep parasite populations low.
Dr. Eric Mussen in his January/February 1992 issue of From the UC Apiaries published a piece called "Varroa Getting Nasty." It seems many beekeepers in California got a surprise when their colonies collapsed last fall. The symptoms at first seemed to be classical for tracheal mites: 1. rapid loss of adults; 2. tiny clusters of bees with a queen; and 3. abundance of stored honey and pollen. Not characteristic was varying amounts of capped brood. The latter revealed that something else was going on; the adults were not being replaced. Developing pupae were killed in their capped cells by mites and never emerged.
To prevent colony collapse, Dr. Mussen suggests checking bees for Varroa two to four times per year. Finding a mite or two doesn't mean the colony is in immediate jeopardy, but it will require treatment sooner or later. And if another check, not too much later, turns up a lot of mites, then you are the unlucky recipient of someone else's failure to detect a problem. Choose your method of colony examination (ether roll, tobacco smoke, Apistan), he concludes, early detection is critical to colony protection.
"Looking for trouble," is the way Dr. Roger Morse categorizes the perpetual hunt for Varroa in the April, 1992 issue of Bee Culture. He concludes, "...in all probability every beekeeper in the continental U.S. and Canada will have infested hives within two to four years." He recommends, therefore, that beekeepers in the U.S., Canada and Mexico check colonies for Varroa at least twice a year.
Although it has been reported that colonies sometimes take years to die after being infested with Varroa, there are exceptions. Dr. Morse speaks of a New York beekeeper whose hives produced over 100 pounds of honey in July and August, yet were dead by late fall. And Dr. Mussen describes a California beekeeper, who after a good producing season, saw 75% of his colonies severely damaged or dead by Christmas. That beekeeper is no longer in business and had to sell out at submarket prices. These cases may be because of drift by bees from nearby heavily infested apiaries that were not treated. Also the fact that mites are hidden and protected in capped brood cells may mean a serious undercount in those found on adults or in bottomboard debris.
Fortunately, detecting Varroa is a fairly simple process. A number of methods are described by Dr. Morse, including: examining brood or adults; sorting through bottomboard debris; and using the ether roll. These are well documented in Varroa Mite Detection, VT 249, produced here at the University of Florida. I can have a copy made and sent upon receipt of a blank VHS videotape.
The technology to determine when a Varroa infestation reaches a treatable level by any detection method currently in use has not been well worked out. Detection results may vary and are dependent on bee/mite population dynamics. For example, in the fall, Dr. Morse says, with little or no brood, you are more likely to find mites on adults, whereas in the spring they will be easier to find in brood. Practical experience by the Florida Division of Plant Industry indicates that when 20 mites in an ether roll of approximately 300 adult bees are found, a colony should be treated with Apistan. However, Dr. Harvey Cromroy of the EntomologyNematology faculty, University of Florida, believes more than five mites is a treatable level. Dr. Morse concludes finding 30 to 40 mites per hundred bees (ether roll) is serious and the colony may be beyond saving. The ability to correlate ether roll with other detection methods is not presently available. For recommended detection levels in Europe see October 1989 issue of APIS. A Varroa quiz was published in August 1990 and current conditions on movement certification in Florida in November 1990.
FLUVALINATE PROS AND CONS
Recently, I've taken to answering questions about the impact of Varroa in Florida by saying there is no problem. This raises a few eyebrows, but in fact with widespread use of Apistan (R), the Varroa problem is under control. And if colonies are not treated by a beekeeper, he/she very shortly has no bees and is also eliminated from the "problem" category (see the article above).
Beekeepers in the U.S. and elsewhere, especially where Varroa was introduced from 1987 on, are extremely lucky. That's because by that year a technology to effectively treat colonies for mites was developed. The formulation was fairly benign to humans and had little potential to contaminate honey. In summary, the development of fluvalinate-impregnated Apistan (R) plastic strips has caused a predicted disaster in beekeeping to become no more than another, admittedly onerous and expensive, management task.
A recent article, however, by Israeli authors Yossi Slabezki, Hani Gal and Yaacov Lensky in Bee Science suggests that Varroa control based on fluvalinate is not without its problems. Writing in Volume 1, No. 4 of the October, 1991 issue, the authors discuss effects of long-range usage of fluvalinate with reference to honey contamination and sub-lethal effects on bee populations. Two procedures in the study were used that are not legal in the U.S. and so will have little direct correlation with methods used in this country: (1) colony infestation level was established by fumigation with fluvalinate smoke strips; and (2) treatment was with Mavrik (R)- soaked plywood inserts, not Apistan (R). In spite of this, however, the study has direct implications for beekeeping in the U.S. Here are some of the recorded observations:
"In most colonies the mite infestation level was reduced from several hundred to 0-10 mites/colony. However, out of each group of 30-40 colonies, one or two still had 30-60 mites/colony.
"Mite populations increased during eight months in all three climatic zones, reaching the highest levels in the hottest region. The different population levels of Varroa mites, however, may not only be due to temperature but to the availability of nectar and colony strength at a particular site.
"Monitoring Varroa populations in a bee yard was useful for subsequent selective control only in heavily infested colonies...If the three (most heavily infested) colonies had then been selectively treated against Varroa, the build- up to a population reaching an average of 256 (+/- 21.3)/colony (in the other hives) might have been prevented.
"Long-term treatment (6 to 8 months) with fluvalinate inserts ...resulted in an almost zero level of Varroa ...Short-term (6 weeks) exposure resulted in increased mite populations. There were no significant differences in the populations of brood and adult bees between the colonies that were exposed to (fluvalinate) 6 weeks or 6 to 8 months. However, the average honey yields per colony were 7 to 15 kilograms (1kg = 2.2 lbs) higher from colonies...exposed to fluvalinate for the shorter interval.
"No detectable residues were found in samples of honey removed from colonies exposed to fluvalinate for 6 weeks. However, in honey samples removed from colonies exposed...for 6 months, the level...reached 0.06 +/-0.05 ppm (parts per million)...above the level established in the U.S. by the EPA."
"In beeswax, fluvalinate residues were higher than found in honey. They reached 0.83 +/-0.77 ppm...in colonies exposed to fluvalinate for 6 months, compared to 0.54 +/-0.21 ppm in wax samples obtained from colonies exposed to fluvalinate for six weeks.
"The placement of fluvalinate inserts at the entrance or inside the brood nest resulted in efficient Varroa mite control in both treatment groups. By placing fluvalinate inserts at some distance from the brood nest combs and by removing them after six weeks, we minimized or eliminated fluvalinate contamination of honey and beeswax." "Under the subtropical conditions of Israel, where egg-laying and brood rearing by honey bees is year- round...two treatments per colony per year are sufficient to keep Varroa mites below a level of economic damage.
"By monitoring colonies for mite populations...we were able to selectively treat only highly infested colonies...to reduce both the number of treatments and the amount of acaricide used in the apiary.
"Sublethal doses of...insecticides, including pyrethroids (fluvalinate is classed as a synthetic pyrethroid) have been shown to modify mating, feeding, and other insect behavior. While a beekeeper may feel that extended treatment might provide prolonged protection from Varroa mites, our data indicate that it will result in reduced honey yields and honey and beeswax contamination at levels above established tolerances.
"Fluvalinate residues in wax from bee colonies that had previously been treated with two Apistan (R) strips...may be due to the increased surface area... 250mm X 30mm X 2 strips, which is about five times greater than that of a plywood insert (180mm X 20mm) as well as increased amounts of active ingredient per treatment.
"In Israel, honey is extracted only from full-depth supers that are separated from the brood nest by a queen excluder. Even though fluvalinate has been used for three and a half years, no traces of the compound have been found in samples of honey in the marketplace."
The authors conclude that beekeepers should be able to reduce the frequency of fluvalinate treatments by carefully monitoring their colonies for mites and only treating those which exceed a certain threshold level. They also state that the possibility of reducing strip surface area and placing strips at the colony entrance could lead to changes in fluvalinate treatment practices. The closing statement: "...development of alternate acaricides, especially those from plant origin, would permit the beekeeper to alternate treatment products, thus extending the life of fluvalinate as a part of an integrated control program for Varroa jacobsoni.
As an epilogue to this study, several qualifying statements must be made. Work at the University of Florida suggests that treatment strips (plywood or plastic) on the bottom board are prone to get wet, even wash away, during rainstorms; placement on the top bars has not been found to be effective. Although less active ingredient is found in Mavrik (R)-soaked plywood inserts, there is evidence that more fluvalinate is released from the wood strips earlier and less later as treatment proceeds. This suggests that plywood, or treatment using any other carrier (e.g. paper toweling), is much more variable than Apistan (R) formulated on slow- release plastic. The above study reveals, for example, that colonies treated for six weeks with plywood inserts had a resurgence in mite populations and the treatment was not uniform in killing mites in all colonies. As far as I can tell "established tolerances" referred to in the study have yet to be fully determined.
Although many continue to believe that they are paying too much for Apistan (R), the benefits beekeepers are enjoying (research and development costs as well as expenses involved in making the material legal to use) are very real. It means a lot to the industry to have a material that, when used according to the label, is certified effective for mite control as well as safe in protecting the honey crop from contamination. As the authors of the above study conclude: "Because beeswax retains fluvalinate residues, because honey and section- honey enjoy a 'natural food' image and because Varroa mites may develop resistance...in the future, it is in the beekeeper's best interest to carefully apply fluvalinate." >. For other comments see December 1987 APIS and the Varroa quiz published in August 1990.
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (904) 392-1801, Ext. 143 FAX: 904-392- 0190
http://www.ifas.ufl.edu/~entweb/apis/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1992 M.T. Sanford "All Rights Reserved
