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Varroa Mite

91-10     
BEEKEEPING INFORMATION
OHIO DEPARTMENT OF AGRICULTURE
Division of Plant Industry – Apiculture
8995 East Main Street
Reynoldsburg, Ohio 43068-3399


VARROA MITE


Cause: The Varroa mite, Varroa jacobsoni is an external parasite of honey bees that attacks adult bees and their developing brood.

Identification: In the life cycle female mites lay up to 12 eggs in a bee brood cell. Preference is for drone cells. However, mite eggs are soon laid in worker brood cells. Nymphal stages of the mite feed on immature bees. After the mites mature, females are fertilized and the males die. Female mites may then alfach themselves to adult bees. Older female mites may move from one brood cell to another, continually feeding and laying eggs. The mites are dark red-brown and measure .04- .08 inches wide, about the size of a pinhead and shaped like a tiny clam shell.

Spread: Varroa was originally confined to tropical Asia. Since 1950 the mite has been found on Apis mellifera in Europe, Africa and South America. South American infestations were thought to be a result of imported queens. In 1987 the mites were first diagnosed in Ohio.

During their life span, adult female mites continue to feed on adult bees. The female mites eventually migrate to bee larvae in brood cells that are about to be sealed. There, the mites lay eggs and renew the life cycle.

In summer, female mites can live for about two months. Later in the year they can live for up to eight months, surviving the winter with clustered bees.

Effect: The mites feed on adult larvae and pupae, weakening the bees and causing disfigurement or death to developing brood. Some bees emerge crippled or with their wings incompletely formed. Heavily infested colonies may show very reduced bee populations.

Detection: Two methods are currently being employed. They are ether roll method and Apistan (fluvalinate) method.

First the ether roll method is a quick and simple diagnostic examination for Varroa mite infestation, It consists of a three part process.

  1. Examine young bees.
  2. Uncap brood.
  3. Use ether roll test.

Examine bees: When a frame is removed from the brood chamber, closely examine the adult bees. Sometimes the mites can be seen crawling on the bees’ thorax or abdomen. However, don’t count on a visual exam only; many times the mites will be hidden within the abdominal segments. It is not necessary to spend excessive time examining adult bees.

Uncap brood: The varroa mites develop within the brood and feed on larvae and pupae. Therefore, it is important to uncap brood, looking at both drone and worker. You might want to remove cell contents from the comb to examine closely. Uncap approximately ten to fifteen cells.

Use Ether Roll Test: When doing the ether roll test a clean jar (pint or quart) and carburetor starter spray (aerosol) are needed equipment. Procedures to follow:

  1. Collect bee sample from brood combs. Fill jar about 1/3 full of bees.
  2. Sample should be from a minimum of 20% of the colonies.
  3. Give bees a short burst of ether. Result: inside of jar is slightly moist with all bees down.
  4. Cover jar and roll bees for about 20-30 seconds.
  5. Examine side of jar for mites.
  6. Dump remaining bees from jar and clean before next test.

The apistan detection method is probably the most effective. A plastic strip impregnated with the pesticide fluvalinate is used to detect the mites. Fluvalinate kills mites, but does not harm bees. Two strips are hung between the frames in a beehive’s brood chamber. If mites are present, they fall onto a white sheet of sticky cardboard placed in the bottom of the hive, where they can be seen.

Control: Presently fluvalinate is recommended to beekeepers for varroa control, trademark being “Apistan” Strip. All honey supers are removed before treatment, however, they can be replaced after treatment. Follow label directions carefully. Other controls are currently being tested for possible use. Apistan can be obtained from most bee supply dealers.

 

Prepared by: Gordon Rudloff
State Apiarist
Ohio Department of Agriculture

Permanent link to this article: http://www.ohiostatebeekeepers.org/resources/ohio-fact-sheets/varroa-mite/

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