Varroa Mite Controls Methods:
Disclaimer: This assay is compiled and intended for educational purposes only. No recommendations or approval is implied for the use of any product mentioned in this assay.
For further information consult with your local State or Professional Apiculturists. A lot of the text and wording is written and copied here is available on the internet.
The Varroa mite (Varroa destructor, formerly V. jacobsoni) parasitizes only honeybees. Its specialized mouthparts enable the mite to feed on bee brood and adult honeybees. The mite brood development is closely synchronized with bee brood development. Without the use of mite controls, the colony will die. The interaction between the honeybee and mite populations is a complex and dynamic process involving many variables. Beekeepers, who use only chemicals as their mite control strategy, will fail. Suppressing the pest population and simultaneously maximizing the bee population requires the implementation of a mite control program that involves the integrated application of management techniques and chemical controls. Such integrated management program is characterized by the following:
1. Successful mite management is accomplished through the combined application of controls, where none would offer sufficient control when applied on their own.
2. A mite control program demands ongoing beekeeper involvement through monitoring and strategizing. Frequent monitoring is essential for making management decisions based on information, instead of speculation.
3. An integrated mite management program aims at keeping mites at manageable levels. Other than killing the colony, mite eradication is not possible or sensible because the colony will be quickly re-infested.
This paper lists chemical and non-chemical Varroa mite controls. Note that physical conditions including temperature, humidity, colony size and condition, time of year, etc., all influence the effectiveness of any control method or product being used.
Fluvalinate (Apistan strips)
• Fluvalinate is the active ingredient of Apistan strips. It is a synthetic pyrethroid applied as a contact miticide. Highly effective during the 1990s, and noted for its low toxicity and ease of application.
• Controls Varroa mites only; not effective against tracheal mites (Acarapis woodi).
• Product delivered in an impregnated plastic strip suspended between brood frames.
• Formulation is not water soluble; no danger of honey contamination. Product is fat soluble and after prolonged use, small quantities will migrate into the wax.
• Product is applied in early spring or fall, outside the period of honey production.
• Widely used throughout the world. Illegal formulations, inappropriate applications, under-dosing, reusing old strips, and un-abated use has led to the development of resistant mite strains in North America and Europe.
• Read label directions closely before use.
• Note: Fluvalinate-resistant Varroa mites have been confirmed in some parts of the continent. The efficacy of fluvalinate may vary. Advice: Contact your Apiary Inspector for details and recommendations.
Coumaphos (CheckMite+ strips)
• Coumaphos is the active ingredient of CheckMite+ strips. The product is an organophosphate, applied as a contact miticide. Highly effective in controlling Varroa mites and noted for its ease of application.
• Care must be taken during application by following label instructions closely. Organophosphates have proven highly effective pesticides, but there have been concerns about persistence in the environment, toxic residues, and applicator safety.
• Product delivered in an impregnated plastic strip suspended between brood frames.
• Formulation is not water soluble; little danger of honey contamination. However, the product's volatility during initial strip installation may cause some absorption in stored honey and wax.
• Note: Coumaphos-resistant Varroa mites have been confirmed in some parts of the country. The efficacy of coumaphos may vary. Advice: Contact your Apiary Inspector for details and recommendations.
• Effective against Varroa and tracheal mites (Acarapis woodi).
• Different application methods and formulations have been developed with variable efficacy.
• Efficacy dependent on factors including size and condition of colony, time of year, humidity, temperature, etc. Efficacy of any one method may range from low to high.
• Formic Acid is corrosive and can cause burns! Rubber gloves and safety glasses should be worn, and inhalation of vapours must be avoided!
• One effective method applied to a two-supered colony in the fall:
• Remove lid and smoke bees off the top bars. Place paper napkins on the top bars and pour acid on the napkins. Prevent dripping. Close the hive.
• Each application equals 30-45 ml (1 - 1.5 fl. oz) of 65% formic acid.
• Apply three to four treatments, four to seven days apart.
• Outside temperatures must be at least 12oC (55oF) in late afternoon.
• Best results when there is no brood in the colony.
• Mite drop can be monitored with sticky boards.
• Formic acid treatments may increase risk of queen loss. Replace queen annually or bi-annually.
• Oxalic acid (Oxalic acid dihydrate) should only be applied in late fall when the colony has no brood. Any open brood in the colony is likely to be killed by oxalic acid.
• Even though the product is not as volatile as formic acid, always wear rubber gloves and safety glasses when handling the product. Avoid inhalation of vapours.
• Oxalic acid treatment should be applied only once.
• Oxalic acid can be applied at cool temperatures, either through vapourization (crystals heated and converted directly into a gas vapour) or trickling an acid-sugar syrup solution onto the bees.
Acid-sugar syrup solution:
• Prepare 1 litre of 1:1 sugar solution.
• Add 35 g of oxalic acid crystals to the warm solution and stir gently until fully dissolved. The sugar syrup solution will have an acid concentration of 3.5%.
• With a syringe or applicator, trickle 5 ml of solution directly onto the bees in each of the occupied bee spaces between frames in each brood box.
• The maximum dose is 50 ml of acid solution per colony whether it is a nuc, single or multiple brood chambered hive.
• Seal all upper hive entrances and cracks, and reduce the main entrance.
• Smoke bees up from the bottom board.
• Place 2 g of oxalic acid dihydrate into the vapourizer. Insert vapourizer through the bottom entrance. Follow manufacturer’s instructions for vapourizer use.
Timing of Application
• Remember that Varroa mites may be quickly re-introduced following a mite control treatment. Timing of treatment is therefore very important. When Apistan or Coumaphos is applied too early in the fall, the end of the 6-week treatment period may be at a time when there is still good flying weather, allowing for mite reintroduction.
• For fall treatment of Apistan or Coumaphos, select the end date of the treatment when the colony has little or no brood left. In warmer areas, the date may be in the first or second week of November. For a 6-week treatment plan, the date of strip installation should then be on or about October 01.
• For many areas, the period of surplus honey comes to an end by mid- end of August. Immediately after honey removal, monitor the colonies for mites. It is recommended to use formic acid as a temporary control measure until strips can be applied later in the fall.
• Alternatively, an Apistan or Coumaphos treatment can be started after honey harvest in late summer, when mite levels demand treatment. The end of the 6-week treatment period would fall on or about October 01. Mites may be re-introduced to the colony but a single oxalic acid application in the middle of November would prevent mites from wintering with the colony.
• To reduce the risk of resistance development, it is recommended to alternate between different control products. Experience has also shown that the efficacy of a product such as Apistan or Coumaphos can be re-established after a couple of years of non-use. (Note that mites are not expected to develop resistance to formic or oxalic acid).
Other Control Products
• Over the years, many other products have been tried to control Varroa mites, including thyme oil, peppermint and wintergreen oils, clove oil, sucrocide octonoate, mineral oil, etc. None of these products have been registered for use in beehives. Do not apply any non-registered products to the colonies from which you will sell honey or other hive products.
• Some control products may have proven effective against mites but may pose a risk of honey or wax contamination, or are hazardous to the beekeeper and the bees.
• Essential oils, including thyme oil, have been reported effective in the control of Varroa. Research so far indicates that these oils are labour intensive and costly, and not consistently effective.
Non Chemical Control
• Non-chemical controls may involve management techniques that hinder the development of the mite population or reduce the risk of rapid re-infestation following chemical controls.
• The 'freezing drone brood method' offers good control but is labour intensive and may weaken the colony. The method depends on the placement of a frame with drone brood comb in the central part of the brood nest (drone brood foundation is commercially available). The queen will be attracted and fill the comb with drone brood. When the drone brood has been capped (> 12 days), remove the frame after all the adult bees have been swept off. Place the frame in the freezer for 24 - 48 hours. Allow the frame to reach room temperature before scratching the drone brood caps. Return frame back to the hive; worker bees will remove all dead drone brood, including dead mites.
• Another Varroa mite control method is the 'queen arrest method' where the queen is temporarily confined to a single brood frame or portion thereof. this method is labour intensive, slows down colony development and may only be suitable for the dedicated, small time beekeeper.
• None of these management techniques offer sufficient mite control on their own but may be used as part of an Integrated Pest Management Program where a range of controls (including chemical controls) are employed.
Physical Control (Traps and Oils)
• Varroa mites cling to their adult hosts and often lose their grip. When mites fall onto the bottom board they will climb up again and return to the bee cluster. The placement of a sticky board on the bottom board prevents mites from returning to the cluster. Sticky boards are commercially available or re-usable sticky traps can be easily constructed at home.
• Screened bottom boards allow mites to fall through, preventing them from crawling back up. The screened bottom board is a passive mite control device which has been reported to reduce mite levels by as much as 40 per cent. Today, most beekeepers use screened bottom boards, with the additional benefit of improved air circulation in the hive.
• It has been reported that strips of cardboard dipped in mineral oil and suspended between brood frames, similarly to Apistan strips, offer limited Varroa mite control. Vegetable oils have been reported to offer good control of tracheal mites.
The Honeybee Tracheal Mite (HBTM) was first introduced into Canada in the late 1980s and has since spread to most of Canada’s beekeeping areas. This microscopic mite called Acarapis woodi, parasitizes adult bees causing the weakening of the colony and increased winter mortality.
• Disease caused by tracheal mites is called Acarine disease, or Acariosis, named after its scientific name Acarapis woodi Oudemans.
• Tracheal mites can’t be seen with the naked eye. Confirmation of infestation requires microscopic examination.
• Infected colonies are most likely to show signs of infestation in spring and fall when mite populations reach their peak.
• In cases of severe infestation, large numbers of adult bees crawl in front of the hive incapable of flight and coordination. Many adults extend their wings outward, often described as “K-Wing”.
• Infected adult bees may be lethargic. Even on good days, a high proportion of bees are in the hive instead of flying.
• Colonies are slow in population build up in the spring and lack vigor. In the fall, a higher than normal proportion of the bee population dies before the onset of winter.
• Colonies show variability in their sensitivity to tracheal mites. Some colonies are resistant and unaffected by tracheal mites, while other colonies may be severely affected and collapse.
• Since the mite introduction, many beekeepers have selected for tracheal mite resistance and in general, the disease is no longer considered serious.
Collection of Bee Sample
• Randomly selected adult bees can be collected in the apiary and placed in alcohol water solution (50%). In case ethanol or rubbing alcohol (propanol) is not available, bees can be temporarily placed in windshield wiper fluid containing methanol.
• Tracheal mite infestations in an apiary are often un-equally distributed. Typically, there are “hot spot” infestations. For this reason, each colony in the apiary must contribute equally to the bee sample being collected.
• A sample of bees from an apiary, regardless of the number of colonies, must contain at least 75 bees in order to detect a general tracheal mite infestation of 2.5 % or higher in the apiary, at 95% confidence (= 19 times out of 20).
• Acarapis woodi is an obligate, endo-parasitic mite affecting the trachea or breathing tubes of the thorax of adult honeybees.
• Using a dissecting microscope in the laboratory, adult bees are placed on their back, decapitated and the frontal section (collar) of the thorax is removed with a surgical blade or pulled with fine forceps. The major tracheae are exposed and can be examined.
• Healthy, non-infected tracheae appear milky-white in color and almost transparent. Infected tracheae are mottled, sometimes bronzed in appearance, and with darkened patches. Higher magnification sometimes allows for the identification of adult mites.
• Light infestation generally involves one tracheal tube affected by mites (mono-lateral) while heavy infestation involves the damaged tissue of both tracheal tubes (bi-lateral).
• Since bees originated from different colonies, the testing results only reflect the condition of the apiary. Reading of these composite samples can only describe low or high infestations or “an apparent absence”.
Control and Treatment
• Before applying chemical controls, closely examine the colonies for signs of HBTM infection. Look for adult bees crawling in front of the hive, lack of vigor, display of K-Wing.
• When symptoms have been noted, a chemical control may be applied without having to collect bee sample for laboratory analysis first. Lab analysis is slow, labor intensive and expensive.
• In Canada, menthol and formic acid have been registered for control of HBTM.
• Apply chemicals only in spring or fall, with honey supers removed.
• Select for tracheal mite resistant bee stock, or purchase resistant stock from a bee breeder.
• Increased incidence and severity of infestation is worsened when bees are stressed. Stress factors may include presence of other diseases, poor forage availability, too many colonies placed in one location causing interference and robbing, lack of feed and pollen, poor beehive equipment, inclement weather, etc.
• Other preventative measures include: don’t collect swarms whose origins are unknown; reduce movement of colonies and avoid high density areas; don’t introduce colonies from infected areas or colonies that have not been tested into the beekeeping operation.
Varroa Mite Detection Methods:
Effective mite control is dependent on frequent and reliable detection. Varroa mites spread rapidly between hives and bee yards due to drifting, robbing and hive movement. Mite levels rise rapidly in late summer and early fall. In heavily infested areas, individual colony infestations can grow from being undetectable to life-threatening levels within a few months.
It is important to monitor mite levels by sampling all or most colonies on a regular basis. Larger beekeepers should sample at least 10% of the colonies in each yard in the spring and the fall. Unusually large or small colonies and those at the end of rows should be tested.
How Often To Monitor
Early detection offers the best opportunity for effective Varroa control. Frequency of colony testing is as follows:
1. twice per year (spring and fall) - when mites are not thought to be around;
2. every two months (excluding winter) - when mites are known to be around.
There are different detection methods available, some more sensitive than others. Some methods require a mathematical conversion to estimate the actual number of mites in a colony. A colony's mite load will indicate the treatment necessary.
The following are a number of detection methods to choose from:
Up to 85% of the mites in a colony are in capped brood cells and not visually detectable. Varroa mites are more attracted to drone brood than worker brood, so look there first. Sample about 100 cells. Locate a patch of drone cells in the purple eye pupal stage. Slide the prongs of a de-capping fork along the comb face and into the protruding drone cappings. Pry upward and remove the pupae. Carefully examine the bodies and the interior of the cells for mites.
Boards are available commercially or can be prepared by beekeepers. The commercial boards are covered with a sticky film and require a screen (8-gauge) to prevent bee entanglement. For home-made preparations, white sheets of paper, cardboard or corrugated plastic (eg. Tenplast) can be cut to cover most of the hive bottom surface (40 x 30cm / 16 x 12in). One side of the board surface should be covered with a 1:1 mixture of cooking oil and petroleum jelly, or the surface can be sprayed with a thin coating of PAM vegetable oil. A cover screen is not required. Boards must be cleaned thoroughly before reusing them to prevent mite transfer. Install sticky board for 24 hours only. When the board is left longer, there will be too much debris, making it difficult to count mites.
Apistan Strips (10% fluvalinate)
Apistan is applied in plastic strips and is a contact miticide. It does not have an effect on mites developing in capped (bee) brood cells. The use of Apistan strips in combination with a sticky board for 24 hours has proven to be a very effective method of determining infestation levels. For detection purposes, use recommendations below under "CheckMite+".
Coumaphos is applied in plastic strips under the trade name CheckMite+. Coumaphos does not kill mites in sealed brood cells. When there is no brood in the colony, the mite count on a sticky board will accurately reflect the colony's infestation level. When brood is present, as much as 85% of the mite population is hidden under the capped brood cells. For detection purposes, use one CheckMite+ or Apistan strip per nucleus or two strips for a standard two-supered hive, where the strips are placed between frames in the central brood area. Daytime temperatures should be 10 degrees C or higher. Strips and sticky board should be removed after 24 hours. For treatment purposes, follow label instructions.
Mite Level Determination: Multiply the number of mites on a board by 6.
Note: CheckMite+ or Apistan trips only used for detection purposes can be re-used 10 times for 24-hour tests before disposing of them. Please make sure that the strips are not exposed to sunlight. When not in use, store in a marked container in a cool, dry and dark place.
Note: There has been and is development of mite resistance to Apistan and CheckMite+
Formic acid is used to control both Varroa and tracheal mites. Several application methods have been developed. It is important to recognize the factors that influence the efficacy of formic acid, including colony size, weather, condition and behavior of the colony, etc. Notwithstanding its variability, formic acid has been recommended for use as a component of overall mite control strategy.
For detection purposes, apply 40 ml (1.5 oz) of 65% concentration formic acid liquid onto several layers of paper towels placed on the top bars of the upper brood chamber. Use enough paper towels to prevent acid from dripping. Install a sticky board and check after 24 hours.
Note: Do not apply Coumaphos, Apistan, formic acid or other chemicals to a hive when honey supers are in place. Use the Alcohol Wash, Ether Roll or Icing Sugar Roll method instead.
Mite Level Determination: Multiply the number of mites on a board by 6.
Alcohol Wash Method
This method is simple, quick and quite accurate when applied to a larger number of colonies in the apiary. It doesn't require a second visit after 24 hours. The test is carried out as follows:
• Use a wide-mouth glass jar and scoop about 300 bees (~1 cup) from the brood area. Make sure that the queen is NOT included!
• Add 50 ml (~ 2 oz) of windshield wiper fluid (or diluted methyl hydrate, or rubbing alcohol) to the jar and shake for several minutes.
• Remove lid and pour contents into a container covered with light metal wire-mesh screen (8 mesh/in) or a coarse sieve. Repeat.
• Pour alcohol solution into a second container covered with cheesecloth or fine sieve. Count number of mites.
Mite Level Determination:
No Brood: Multiply by 100 to estimate the total Varroa mite population.
Plenty of Brood: Multiply by 600.
This test is simple but less accurate than the Alcohol Wash method because it is more difficult to obtain an accurate count of the number of mites in the sample.
• Select a brood frame with plenty of adult bees, and preferably with drone brood. Make sure the queen is NOT on the frame!
• Gently scrape 150-300 young bees from the frame using a wide-mouth jar.
• Apply a two second burst of ether (automotive starter fluid) into the jar, replace the top and shake vigorously for 30 seconds.
• Gradually rotate the jar horizontally and look for any mites sticking to the sides. Normally, the ether causes the bees to regurgitate, making the sides sticky. If not, add a bit of syrup or water.
Mite Level Determination:
No Brood: Multiply by 100 to estimate the total Varroa mite population.
Plenty of Brood: Multiply by 600.
Icing Sugar Method
Instead of Ether Roll where all the bees are killed, icing sugar can be used.
Procedure is as follows:
• Collect a lightly packed cup of bees (about 300 bees) from a frame of uncapped brood.
• Quickly place bees into a wide-mouth jar fitted with a 1/8th wire mesh screen lid.
• Place two heaping tablespoons of sugar powder through the screen.
• Shake jar thoroughly, tip it and shake five times like a salt shaker.
• Dump the sugar containing the mites on a white flat surface.
• Repeat the above two steps until virtually no more sugar shakes out.
• Count the mites.
Mite Level Determination: When 5 mites or more are counted, treat the colonies.
When to Treat?
After determining an estimate of the total number of mites in a colony, it must be decided if and when to treat. In the spring, before honey supers are in place, or in the fall, when honey supers have been removed, treat when 15 mites or more are counted.
When honey supers are in place, use the following guidelines:
# Mites/Col. Recommendation
less than 100 *not an immediate problem * treat in September and October, after honey removal
continue to monitor bimonthly
100 - 999 *mite infestation will have an economic impact *treat as soon as possible after removing honey; start in August, even if some crop potential is lost (winter bee population must be protected) continue to monitor bimonthly
1000 mites + *colony collapse imminent *remove supers and treat immediately *treat again in October
Pettis Test-Detecting Varroa Mite Resistance to Apistan and Coumaphos
Disclaimer: This assay is intended to screen for resistant mites and is not intended to indicate the exact level of resistance.
The information on this assay has been modified (from internet sources) Dr. J. Pettis of USDA-ARS Bee Research Laboratory, Beltsville, Maryland ([email protected])
This test can be used to determine mite resistance when a beehive doesn't appear to respond to chemical mite control measures. It uses fluvalinate (Apistan®) or coumaphos (CheckMite+TM) strips and can test both products simultaneously on the same group of colonies by taking two samples from each hive. Each sample, whether Apistan or coumaphos, requires one jar.
Materials required for each test:
• 500ml jar with lid (wide-mouth canning jar)
• light metal mesh cover for the jar (8 mesh to the inch hardware cloth)
• index card (or similar) and stapler
• 3/8" X 1" piece of a new Apistan® or CheckMite+TM strip
• 1/4cup (60 ml) measure to scoop up bees
• 25% alcohol or windshield washing fluid
• straining cloth and 6 clothes pins
• plastic or rubber gloves
• plastic bucket
• sheet of white paper
Staple a 3/8" X 1" section of an Apistan® or CheckMite+TM strip to the center of an index card. Make sure to handle the Apistan® and CheckMite+TM with gloves. Place the card in a jar with the section of the Apistan® or CheckMite+TM strip facing inwards. Replace the solid, round metal section of the canning jar lid with a piece of wire mesh. The holes in the mesh should be large enough to let Varroa through easily.
Shake bees from one or two brood combs into an up-turned hive lid, bucket or box. Scoop up 1/4 cup or 60 ml of bees (~150 bees) and place them into each jar, being careful not to damage the bees. Screw the lids on the jars to stop the bees from escaping.
Place the jars in an incubator or a warm room, in the dark, for 6 hours. Alternatively, place jars in a picnic cooler with a couple of hot water bottles. Refill the bottles with hot water after the first 3 hours. Make sure the lids of the jars are not covered so that the bees have air.
After 6 hours, hold the jar about 10cm above a piece of white paper and turn upside down so that the mesh lid is facing downwards. Hit the jar with the palm of your hand three times. Count the number of mites that fall on the paper.
Knock the bees to the bottom of the jar. Remove the index card with the attached strip and fill the jar half-way with alcohol or washer fluid. This should be done outside, using gloves. Remove the mesh lid and replace with the original solid lid for the jar. Shake the jar vigorously for 5 min.
Remove the solid lid and replace it with the mesh lid. Pour the fluid into the straining cloth pinned to the bucket. Refill the jar with fluid, swirl the bees around and pour through the strainer again.
Count the number of mites recovered on the cloth. If the total number of mites recovered in both samplings (Apistan®, CheckMite+TM) is less than 5, the results should be discarded.
To calculate the percentage of mites killed by Apistan® or CheckMite+TM, divide the number of mites that initially fell on the white paper before the bees were killed, by the total number of mites (total mites = white paper mite count + mite count from bee washing).
%kill by Apistan® or CheckMite+TM = initial kill, divided by total mites x 100
Resistance Test with Bees
If more than 50% of the mites were killed by the Apistan® or CheckMite+TM after 6 hours, the mites are susceptible and adequate mite control can be expected. If less than 50% of the mites are killed after 6 hours by Apistan® or CheckMite+TM, the mites are resistant to Apistan® or CheckMite+TM.
Critical Factors for the Success of the Resistance Test
• Prescreen hives using the ether roll technique (250-300 bees) and test only hives yielding 5 or more mites. This test gives meaningful results only when performed on hives with adequate mite levels. Do not expect levels of resistance to be the same among hives. Select 12 hives per apiary. More hives are better. This test is not designed to identify individual hives showing resistance. Use apiary averages to assess the results.
• Perform the test exactly as described. Jar size, size of Apistan® or CheckMite+TM pieces and temperature are important.
• Ensure that bees are mobile in the jars so they contact the strips. Cool temperatures may cause the bees to cluster away from the strips. If using darkened incubator, it may be helpful to open the incubator periodically to admit light and fresh air to encourage bee movement.
• It is best not to reuse strip pieces or index cards. Wash jars between tests.
Note: Do not expose jars with Apistan® or CheckMiteTM to sunlight for any length of time. It is best to keep the jars in their storage boxes before and after filling until they are incubated. Sample bees from brood frames. For accuracy and to avoid bee injury, use a measuring scoop. Do not scrape bees directly into jars.