Bee Brothers Apiary
Silver Bay, New York
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Bee Diseases & Pests: Varroa Mites
Varroa mites are small tick-like parasites that are
native to Asia. There, they use the Asian honey bee
(Apis cerana) as a host. With the shipping of bees
worldwide, there are only a few places that remain
mite free. They were first discovered in the U.S. in
1986 and quickly spread throughout North America.
An adult mite, about the size of a pinhead, is visible with the naked eye. The adult female mites survive on the adult bees. The mite will pierce the bee's exoskeleton in soft spots, usually between the abdomen segments, and feeds on the hemolymph. Young, developing mites feed on the developing bee pupa.
The mites reproduce by the female mite entering the brood cells with the developing larva shortly before the cells are capped. Female mites tend to gravitate to drone cells rather than worker cells. More than one mite can enter into each cell. Once in the cell she will bury herself in the remaining royal jelly. After the cell has been capped for approximately 60 hours the female mite will begin laying eggs. She will lay eggs in 30 hour intervals. Typically, the first or second egg will develop into a male and all the rest will be female. It takes about 5-8 days for the mites to develop. Male mites develop approximately two days early than female. The newly developed mites will mate in the cell, as a result, if only one reproductive female entered the cell, will the young mites will be unable outbreed. Only fully developed mites will emerge with the adult bee and survive outside the cell. The males and immature mites will remain in the cell and die. Because the worker bees take 21 days to develop and drones 24, the reproductive cycle of the varroa mite is more suited for the drone brood. In fact, on average 1.8 fully developed mites emerge from a worker cell, while 2.7 mites emerge from drone cells. It is this fact that makes it important to monitor the quantity of drone cells you have in the hive.
Controlling varroa mites is a challenge. There are chemicals on the market that can be used. These have varying degrees of effectiveness. For years, Apistan was used and very effective; however, now many beekeepers are reporting the mites have become resistant to Apistan. As a result, many beekeepers have turned to Checkmite, which because of it's toxicity is only on emergency approval from the EPA. Yet again, beekeepers are reporting the mites have developed resistance. Resistance to both Apistan and Checkmite varies from region to region.
There other means to control varroa mites, some chemical and some non-chemical. There are several methods that have not met with EPA approval, such as formic and oxalic acid. As these have not been approved, we do not recommend their use, or any other non-approved treatment. There are approved alternatives to the hard chemicals, Sucrocide is just one of a few. This is a very effective method of treatment; however, it is difficult for beekeepers with numerous hives to use. It is very time and labor intensive. Each frame must be removed and sprayed 3 times on a 7-10 day cycle. For a beekeeper with only a few hives this is a very effective form of treatment.
Integrated Pest Management (IPM) is a method of controlling mites by using the biology and life cycle of the mite to the beekeepers advantage. No one single IPM technique will solve the mite problem, rather, several techniques must be using together. Together, benefits of the IPM techniques are often greater than the sum of the individual parts. A few examples of IPM techniques are screened bottom boards, drone frames, and interrupted brood cycle.