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OSU Honey Bee Lab
Wooster, Ohio
Fact Sheet:Controlling varroa mites in a bee hive
| Call no.: | Unknown |
|---|---|
| Author: | James E. Tew, David J. Heilman, Jason G. Ferrell |
Varroa mites (Varroa destructor) were first recorded in the United States in 1987. By 1992–1993, Varroa mites had become widely established in Alabama and have continued to cause extensive bee colony deaths. The Varroa mite is a reddish-brown, external honey bee parasite about the size of the head of a pin. Varroa mites attach to adults and developing brood, where they feed on their blood. If left untreated, Varroa mites can deform bees and eventually kill the colony.
Contents |
Symptoms
Varroa mite symptoms include:
- Disfigured adult bees (deformed legs and/or wings),
- Mite infested capped drone brood,
- Bees discarding larvae and pupae,
- Spotty brood pattern,
- Reddish-brown spots (adult mites) on white pupae,
- Cells being uncapped and destroyed.
Some beekeepers describe Varroa infestations as being similar to foulbrood but without the smell.
A second comparison of a Varroa kill is to that of an insecticide kill. Colonies can die so fast from high Varroa infestations that thousands of dead bees will pile in front of the hive—a symptom usually reserved for pesticide kills. Most problems with Varroa mites occur in the fall. They need bees (either immature or adults) to survive and, without bees, will die within a few days. Therefore, combs, frames, and equipment is safe to reuse. Wait approximately 7 days before reusing.
Inspecting a Hive for Varroa
To inspect for Varroa mites, check pupae for reddish-brown spots (adult Varroa). It is best to open capped drone brood for this inspection though capped worker brood can also be used.
A second method for surveying for mites is to collect about fifty worker bees in a canning jar and spray them with a 2-second burst of automobile starting fluid (ether). Most auto-parts stores have starting fluid sprays. The spray will kill test bees and any attached mites, causing then to fall from the bees. Swirling the treated bees for 10 seconds will cause dislodged mites to stick to the side of the jar where they can be counted. If even ONE mite is found, begin Apistan strip treatment as instructed below, and then maintain a regular treatment cycle.
Treating for Varroa Infestations
Apistan (fluvalinate), along with specific instructions for use, is available through all major bee suppliers. Generally, the Apistan label calls for two fluvalinate-impregnated plastic strips to be hung in each hive body between frames 3 and 4 and frames 7 and 8 for at least 42 days (six weeks). During treatment with any drug or pesticide, all honey supers for human consumption MUST be removed.
- Important:
- No other chemical compounds other than those listed in this leaflet are approved for use in bee hives.
- Always follow label instructions for handling and applying any chemical in the bee hive. Dispose of waste chemicals as directed on the label instructions.
- Never have any type of disease or pest treatment program underway while surplus honey supers are on the hives.
- Rate:
- Use one strip for each 5 combs of adult bees in all deep brood chambers. Strips should never be in supers.
- Exposure Time:
- For Survey -- leave strips in the hive for 7 days (to see if Varroa is present).
- For Treatment -- Install strips 8 weeks prior to the beginning of the spring flow. (See Comments and Suggestions below)
- Treatment Period:
- 42–56 days (6–8 weeks)
- Location:
- In a single deep hive having 10 frames of bees, place one strip between frames 3 and 4 and between frames 7 and 8. Attach strips with staple or thumb tack. Strips also have a tab that can be used to support themselves between frames.
Comments and Suggestions
- Strips MUST be in contact with brood nest bees at all times for them to be effective.
- Though Apistan is safe, wear gloves when handling strips.
- Though the treatment cost is twice as great, beekeepers have reported greatly improved results if the entire treatment procedure is repeated as soon as the spring honey crop is removed.
Alternative Treatments
Treatment with Apistan strips has proven successful against varroa infestation in the past, however mite resistance to the active chemicals in Apistan have become a recent problem. Other treatment options include coumaphos (CheckMite+), formic acid, and thymol. It should be noted that, while these different chemicals are used for similar purposes, neither their potential dangers nor their efficacy are necessarily equivalent. For example, the USDA recognizes coumaphos as posing a moderate hazard to honey bees and a serious health risk to humans if handled improperly. It is imperative to follow manufacturer instructions while using any chemical treatment.
Testing for Chemical Resistance
Required Materials
To prepare the equipment, fashion the hardware cloth into circular pieces that can substitute for the original lids of the mason jars. Set the original lids aside, as they will be needed later. Next, cut small (3/8x1”) pieces of the Apistan or CheckMite+ strip to affix to separate index cards. Each index card is then placed into its own jar, with the chemical strip facing toward the interior of the jar.
To begin the test, select a frame of bees from within the brood nest area of the infested hive. If the queen is present on the frame, return her to the hive. Shake the bees into a cardboard box, then scoop ¼-cup (2 oz.) of bees into the jar. Affix the mesh lid and allow the jar to set in a warm, dark area.
Note: It is important that the temperature of the storage area is warm enough that the bees move around, thus coming into contact with the strip. Also, exposing the strip (of either chemical) to sunlight for any length of time can render it inert.
After six hours, hold the jar upside-down over a white piece of paper and strike it three times using the palm of the hand. Record the number of mites that fall on the paper.
To calculate the percent of mites killed, it is necessary to separate the remaining mites from the bees. This can be accomplish by washing the bees with alcohol or by incubating the jars at 105–115°F (40–45°C) . Using the incubation method, jars should be placed upside down over sticky paper. This should cause the mites to fall from the bees onto the paper, where they can be counted.
Alternatively, the jar can be filled half-way with an alcohol solution and shaken for five minutes (after replacing the mesh with the original lid). After shaking, replace the mesh lid and pour the liquid over a straining cloth. Refill the jar with water, swirl it around, and pour out a second time. Count the mites on the cloth and record the number.
To determine the efficacy of the chemical treatment, the number of mites initially collected is divided by the total number of mites collected. If the chemical treatment eliminates less than half of the total number of mites, the mites are resistant to that treatment. If more than half of the mites are killed, the chemical is a successful treatment.
Disclaimer
Use pesticides only according to the directions on the label. Follow all directions, precautions, and restrictions that are listed. Do not use pesticides on plants that are not listed on the label.
The pesticide rates in this publication are recommended only if they are registered with the Environmental Protection Agency or the Alabama Department of Agriculture and Industries. If a registration is changed or cancelled, the rate listed here is no longer recommended. Before you apply any pesticide, check with your county Extension agent for the latest information.
Trade names are used only to give specific information. The Alabama Cooperative Extension System does not endorse or guarantee any product and does not recommend one product instead of another that might be similar.
For more information, call your county Extension office. Look in your telephone directory under your county's name to find the number.