Volume 5, Number 10, October, 1987

Copyright ©1987 M.T. Sanford "All Rights Reserved"

In this issue:

Varroa Found in Florida
Varroa Life Cycle
Quarantines and Controls for Varroa
Sampling for Varroa
Sanitation Issues
Damage and Symptoms

VARROA INTRODUCED TO FLORIDA

Introduction of the Asiatic bee mite (Varroa jacobsoni) is a nightmare come true for the North American beekeeping industry. Even as I write this, many persons are in a state of shock. As of this date (10-20-1987), some nineteen of Florida's sixty seven counties have had positive finds. Latest information is that there has been confirmation of the mite's presence in the states of Pennsylvania, Ohio, Illinois and Wisconsin. The great majority of finds so far have had some kind of Florida connection.

As a first step in attempting to assess the situation, the Commissioner of Agriculture on the advice of Varroa Mite Task Force and the Honeybee Technical Council (see the August 1987 issue of APIS for a discussion of bee committees and their duties) has placed a two-week moratorium on bee and beekeeping equipment movement. This is to try to get an idea of the mite's present distribution. Emergency teams made up of Florida bee inspectors and APHIS (Animal Plant Health Inspection Service) of the U.S. Department of Agriculture are now combing the state for infested colonies.

Whether the moratorium will be continued and what will be the Department of Agriculture's reaction to these surveys is only conjecture at this moment. Meanwhile Mr. Henry Will, President of the Florida State Beekeepers Association, has sent an open letter to the membership encouraging every concerned beekeeper to become involved by keeping abreast of all information and contacting their elected representatives on the issue.

It is extremely important to ensure that Varroa is not confused with the tracheal honey bee mite (Acarapis woodi), first found in 1985. There has been and continues to be a great deal of controversy about the latter mite which lives in the breathing tubes of bees. It is difficult to find and the damage it inflicts on colonies is a matter of great debate. At present there is no legal chemical control and experiments on a number of aspects of the biology and control of this mite are continuing. Both the general and beekeeping public, however, may think the present mite crisis is a continuation of the tracheal mite affair. THIS IS NOT SO!

The Asiatic bee mite (Varroa jacobsoni) is another story entirely. There is near unanimous support that it is potentially the most serious pest ever to threaten U.S. beekeeping. As evidence for this, consider that both Canada and Mexico have sealed their border to U.S. bees because of the recent finds. Reports from other areas where the mite has been introduced, especially temperate climatic regimes, indicates great losses of colonies have occurred.

A good deal of information is available on the Asiatic bee mite (Varroa Jacobsoni), but there is much to be learned. Perhaps the most authoritative review has been published by W. Ritter of the German Federal Republic ("Varroa Disease of the Honeybee Apis mellifera," Bee World, Vol. 62, No. 4, 1981, pp. 141-153).

According to Dr. Ritter, the mite parasitizes the European honey bee (Apis mellifera L.) whenever it comes in contact with it and sometimes does great damage, far more than when it parasitizes other honey bees such as Apis cerana, the Asian honey bee. Because colonies of European bees do die from parasitism by Varroa, this indicates the development of the host(bee)/parasite(mite) relationship is not complete and thus, the mite's effect can be much more severe than that of other parasites.

LIFE CYCLE OF VARROA

Numerous studies have pieced together the life cycle of the Asian honey bee mite, but it has yet to be cultured artificially and many aspects of its complicated biology are unknown. The adult female leaves the brood cell and attaches to an adult worker or drone where she begins to feed by cutting a hole in the intersegmental membrane of the bee's hard outer skeleton. Little is known about the length of time required for this phase. Next, the well-fed female drops off the adult into a brood cell and hides in the brood food (jelly). Normally, once the brood food is consumed, the female then begins to feed on the larvae itself by piercing its delicate skin. She then lays a number of eggs of both sexes which hatch into six-legged larvae. After 48 hours, the larvae molt into an eight-legged protonymph which, after feeding on the bee larva, molt into a feeding deutonymph. Three days later, the last molt to an adult occurs. Approximately twenty-four hours later the mites mate inside the capped honey bee brood cell. The males die after copulation in the brood cell and the female mites emerge to begin the cycle again.

Developmental timing in both the honey bee hosts and parasitic mite is extremely important in determining resulting infestation levels of mite populations. There is evidence to show that shorter development times in bees do not allow the mites to fully complete their life cycle, thus interrupting population growth. This is particularly true for tropical races of bees, including Apis cerana and Apis mellifera scutellata (African/Africanized bees).

The above details and concerns have been reviewed in "Developmental Phases in the Life Cycle of Varroa jacobsoni, an Ectoparasitic Mite on Honeybees," by W. Ramirez and G. Otis, Bee World, Vol. 67, No. 3, 1986, pp:92-97.

QUARANTINES AND CONTROLS:

According to Dr. Ritter, spread of Varroa has been largely caused by transport of bees and suggests the following:

1.  Develop and use more effective treatment methods
2.  Control importation of all species of honey bees
3.  Diagnose infestations in the latent stage (before damage is seen)
4.  Isolate infested colonies and those in the immediate area
5.  Control and coordinate treatment of infested colonies

Worldwide, most control is now accomplished by chemicals, however, not all authorities agree on specific control measures. Many of the chemicals used in other parts of the world could not be labelled in the United States, and those that have possibilities might require two years before a label is acquired.

Dr. Ritter counsels the following concerning control. The aim in the German Federal Republic has been to isolate the source of infestation and eradicate the mite in specific localities. However, where it has been spread over a wide area, infestation can at best only be reduced, particularly where there are feral colonies. A further danger lies in the uncontrolled use of chemical agents for treatment. Unsuitable highly toxic substances are coming into use and their improper application can contaminate honey. Frequent underdosing can also result in resistant strains of mites, already observed in Japan with phenothiazine. Frequent use of chemicals can also make beekeeping unprofitable, says Dr. Ritter, and a biological control should be a first priority in research for a long-range answer to Varroa control.

SAMPLING:

Beekeepers in Florida are encouraged to sample their own bee colonies for presence of Varroa. The mite is the largest associated with honey bees, about the size of a "seed tick," and visible to the naked eye. The mite may be confused with the bee louse, Braula coeca, which has been reported in Florida.

The following methods are recommended for detecting Varroa in a colony, according to M. Delfinado-Baker, USDA, ARS, Beneficial Insects Laboratory, Bldg 476, BARC East, Beltsville, MD, 20702:

Adult female mites are pale to reddish brown and measure about 1.1 millimeters long by 1.5 millimeters wide.

1.  Examination of hive debris:  
 
    a.  Collect debris from hive floor with brush and dustpan and examine
        on a sheet of white paper.
 
    b.  Immerse dried debris in 95% alcohol and examine for mites which may be 
        seen floating or sinking to the bottom.
 
2.  Examination of adult bees:
 
    a.  Collect 50 to 100 bees from open brood comb.  Place in washing 
        solution- gasoline, 25% ethanol or isopropyl alcohol, detergent-water 
        mixture or hot water, and shake vigorously for 1 to 10 minutes.  
        Recover mites by straining through fine screen mesh.
 
    b.  Collect 100 live bees from open brood comb.  Place in small cage with
        wire mesh bottom on white paper.  Place in oven at 46-47 degrees C. 
        (114-120 F.) for 10 to 15 minutes and examine white paper.
 
3.  Examination of brood cells and combs:
 
    a.  Uncap brood (drone brood is preferred by the mites, but they can
        also be found on worker larvae) and remove white pupae with forceps.
        The mites are easily seen against the white color of bee larvae and/or 
        pupae.

Florida inspection teams have had good success doing the following: Put about 1/3 pint of live bees from the brood comb in a glass jar, add a one-second squirt of ether and alcohol (commercial engine starting fluids can be used), shake and roll bees around in jar. Look for mites on side of glass jar. Mites are reddish in color and uniformly shaped. It is emphasized that bees sampled MUST COME from the brood nest, NOT the entrance.

SANITATION:

Although the possibility of mites being transferred from one hive to another by humans is considered slight, this cannot be totally discounted. Division of Plant Industry personnel are aware of this and especially prepared to carry out adequate sanitation procedures between suspected colonies. Should a beekeeper suspect the presence of Varroa in a colony, the best plan of action is to immediately notify the nearest apiary inspector or Chief Apiarist above for further advice on sanitation procedures.

DAMAGE AND SYMPTOMS:

Bees in temperate climates with harsh winters appear to be more at risk than populations in other climatic zones, however, most authorities agree that all European bees in the U.S. (Apis mellifera) that become infested with Varroa must be considered to be in extreme jeopardy. The most observed symptom of the disease is deformed larvae, pupae and adult bees which are usually thrown from the colony and can be seen near the entrance.

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
©1987 M.T. Sanford "All Rights Reserved

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