Varroa Destructor
Facebook like
Facebook share

 

Quick links to:

Apistan/Apivar Numerous interesting articles on the treatment for Varroa
Formic Acid
Oxalic Acid Build a Varroa floor
Thymol
Biotechnical Methods Tools for Varroa management -
A Guide to Effective Sampling & Control
Sugar Dusting
An historical record from 1988 - 1992 of the spread of Varroa World Wide.
Listing some of the early anti Varroa treatments tested.
Including the original design of the Thermal Cabinet used successfully in Russia from 1977

 

Economic Importance

In the UK, severe losses have been encountered resulting in the loss of entire apiaries. Infested colonies will usually die if left untreated, and colony loss may occur within a few months after infestation. In addition to the economic losses incurred by beekeepers, fruit and vegetable growers who depend upon bees to pollinate their crops could suffer shortages.  There has also been a similar reduction in feral/wild bee colonies ... It's difficult to believe that Noah only took two Varroa mites into the Ark

Mite Biology

Varroa mites attack honey bee colonies as an external parasite of adult and developing bees, by feeding on hemolymph (fluid of the circulatory system similar to blood), spreading disease, and reducing their lifespan. Evidence suggests that Varroa and their vectored viruses affect the immune response of honey bees, making them more susceptible to disease agents. For more information on this topic see here.  Reproductive Varroa mite on a developing pupa (reddish oval) and two immature Varroa (opaque ovals). Credit: Abdullah Ibrahim (arrows added for emphasis)

Mature female Varroa mites survive on immature and adult honey bees (worker, drone, and rarely queen), are reddish brown, and about the size of a pin head. Male mites are a smaller size and tan color, do not feed on bees, and are only found inside brood cells.
Varroa have two life stages, phoretic and reproductive. The phoretic stage is when a mature Varroa mite is attached to an adult bee and survives on the bee’s hemolymph. During this stage the mite may change hosts often transmitting viruses by picking up the virus on one individual and injecting it to another during feeding. Phoretic mites may fall off the host, sometimes being bitten when bees groom each other, or it may die of old age. Mites found on the bottom board of the hive or that fall though a screen bottom board are called the “natural mite drop”. But these mites that fall off of bees represent a small portion of the total mite population because the reproductive mites are hidden under cell cappings.

A "mother" mite may lay an egg every 36 hours on the side of a cell. The first egg usually hatches into a male and stays within the cell. The other eggs hatch into females and feed and grow within the cell. Next, they mate with the male and emerge from the cell when the bee emerges.

The mother mite will seek out another cell while her daughter mites may hitch a ride on an adult bee and feed for awhile before finding a new larval host. Mite populations increase slowly when starting from just a few mites, but the hitchhiking behaviour of the mite can spread large numbers of mites with drifting or robbing bees causing a hive to quickly become heavily infested. When a larvae is infested by two or three mites, it will usually die. As a colony reaches a point of collapse, bees sometimes abandon the hive and carry mites to neighbouring hives.
For a more indepth description see: Varroa Mite Reproductive Biology also Biology and control of Varroa destructor  (1Mb)

This is called "Re-infestation" and can cause a beekeeper who has looked after his hive and reduced varroa to less than 5%, to find his hive now infested back to 95% and on the point of collapse. Varroa mite on Larvae

 

Detection

Detection and monitoring are the first steps toward control. Even if you think your bees are not infested, check regularly every two months. Following are the common detection methods:

1. Extract drone brood with a de-capping fork and visually examine larvae and cells for mites.

2. A reliable method uses Apistan/Bayvarol strips. Place a piece of stiff white paper sprayed with aerosol cooking oil/something sticky, on the hive floor. Insert strips of Apistan according to label directions. Check the paper in one hour. If there are no mites, check again the next day. Extract drone brood with a de-capping fork

3. Trickle oxalic acid over the top of the frames in a 5% solution

Strategies for effective varroa control

1. Regularly monitor the infestation level in your colonies. This will warn you if the mite population is building up to a damaging level faster than expected, or if your control methods are not proving effective. Don't just treat and leave it to chance.

2. Don't assume that a single chemical treatment or a single biotechnical method will always provide sufficient control. Practise integrated control of varroa, using a combination of methods each working in different ways and at different times of the year. This will give you the most effective control.

3. Try to co-ordinate treatment programmes with other beekeepers in the area, to reduce mite re-invasion problems. Your local beekeepers' association will be able to help organise this.

4. Never leave infested colonies unmanaged. They will eventually be killed by varroa and in the meantime they will re-infest the colonies of other local beekeepers who are trying to control infestation. If you can't manage your bees, you should consider selling or giving them to others who can.

5. Be prepared to be flexible and adaptable and change your control programme as circumstances dictate

 

Control

Control measures are advised if any mites are detected in any hive in an apiary and hence on all hives within that apiary.

However it is impossible to apply treatments with substances suspected of leaving residues in honey during the honey flow period which is between April and the end of August.

Below is a table of natural mite drop.

Natural mite drop per day
Infestation level
1
Low
1 - 10
Acceptable
11 - 30
Approaching tolerance level
30
Liable to collapse

If your hive is approaching tolerance level or in danger of collapse, remove what honey you might have and treat.

 The 'Central Science Laboratory' or CSL have set up a 'beebase' on their web pages for anyone to check their varroa mite drop over a period of time and gives recommendations for treatment dependant on your mite drop.

Click here to find the pages

 

This video shows the juxtaposition of the life cycles of the honey bee and the varroa mite. It was created by Jeff Harris of the Agriculture Research Service.

 

What to treat with ?

Apistan/Apivar

Strips impregnated with chemicals ... (Apistan - Taufluvalinate/pyrethroids and Apivar - Amitraz), and are placed within the hive. Manufacturer's instructions on the packet should be followed precisely. Leaving the strips in longer than recommended will lead to resistant mites developing.

These chemical residues are not permitted in honey.

Chemical residues due to Apistan/Apivarl treatments, present on wax surfaces, continue their action even after the end of treatment. Thus, they prevent normal development of the varroa population. This is the reason why it has been observed in the majority of apiaries treated with pyrethroids in the past that the mite fall is 2 to 3 times smaller than in apiaries treated with alternative methods.

Many beekeepers in the UK are now reporting that they have resistant mites, making Apistan totally ineffective.
Apivar is not licensed in the UK as such ... however it is used on mainland Europe and under present legislation, a veterinary can issue a prescription for individual use by beekeepers.

One such veterinary is Robert Thurlow, BVetMed MRCVS, who will issue a prescription and supply Apivar

Contact:Robert D. Thurlow BVetMed MRCVS
Ark Vet Centre Ltd
51 Glasgow Street
DUMFRIES
DG2 9AG
Tel:  01387 259111   e-mail: Robert Thurlow   Web site: Ark Vet Centre

Formic acid

Formic acid is the only treatment for varroa that penetrates the wax cappings of sealed brood to kill the mites. Formic acid also controls wax moth and acarapis woodii (tracheal mites)

There are various formic acid dispensers that are commercially available ... Apidea - Nassenheider - Liebefelder - Universal evapourator - Krämerboard.

Krämerboard

The use of the Krämerboard is one of the most popular methods and is used by 60% of the beekeepers in Denmark.
      The Krämerboard involves putting 60ml of 60% formic acid on a 20 x 24 x 1.5cm piece of soft fibre building board or absorbent flat 'kitchen' sponge, then sealing it in a plastic freezer bag.

Assuming a strong colony covering 10 frames and calculating at 2ml of acid per frame

  1. Day 1 ... Place the flat sponge on the wooden strips, carefully squirt 20mls 60% acid onto it.
  2. Day 4 ... Carefully squirt another 20mls, 60% acid onto the sponge.
  3. Day 7 ... Carefully squirt another 20mls, 60% acid onto the sponge.
  4. Day 10 ... Remove the sponge

The total payload is 60mls

Buying Formic acid at 85% solution and wanting to dilute to 60% ?

  • Dilution problems are needlessly intimidating
  • Concentration x volume = amount
  • Diluting a volume of a solution does not change the amount of the solute.
  • Starting concentration (C¹) times starting volume (V¹) must equal final concentration (C²) times final volume (V²):

Therefore  … C¹V¹=C²V²

*** When mixing always pour the acid into the water
and NEVER the water into the acid ***

 

Nassenheider evapourator

Nassenheider evaporator

Nassenheider evapourator was developed for slow continuous evapouration of 60-65% formic acid for combating varroa mites

 Filling a Nassenheider evaporator

Evapourator fixed into a frame and being filled with Formic acid

This evapourator is placed close to the focus of bee activity and the brood. Bees regulate a constant temperature of 35°C next to the brood, that is why the evapouration rate is largely independent of external temperatures

Conditions for effective control

Brood should be present for all formic acid application and wire mesh floors should be blanked off. Treatments when temperatures exceed 25°C are not advisable as evapouration rates might get too high causing damage to bees. For the Nassenheider evapourator temperatures should not drop under 5°C

Time of application

It is normal to apply formic acid in July, August and September. The first application should take place after honey harvest (give them some sugar first), the second application directly after wintering is completed.
Research shows that formic acid can also be used in spring, for example in combination with swarm prevention.

Efficacy

Formic acid has a knockdown success rate of 85% to 98%. At low evapouration rates the efficacy is lower. Use a floor insert a few weeks after the treatment and check effectiveness.
Optimum efficiency is obtained when treatment begins in late summer after the honey flow, and when ambient temperature is 18-25°C, with minimum night temperature no lower than 12°C

Bee tolerance

Formic acid damages the brood and causes some bee mortality, but both effects are negligible. Drones however are hindered by formic acid. Do not use formic acid in colonies purposely used for drone production. A further drawback is the use of a high 85% acid concentration causes loss of queen bees.

Safety measures

Formic acid is a corrosive chemical that is potentially hazardous to humans unless proper precautions are taken and needs to be handled very carefully with full protective clothing. Avoid skin and eye contact as well as inhaling vapour. Always wear protective gloves and safety goggles. When using formic acid use a gas mask. Dust masks are not sufficient. The acid also damages clothes.

Residues

Honey contains naturally low levels of formic acid, ranging from 5 to 600ppm, depending on the type of honey. Formic acid used for varroa control in autumn results in increased formic acid in syrup stores and honey, although levels drop to those normally found in honey after a few months. Autumn treatments can be recommended without affecting honey quality, although spring treatments should only be made on an emergency basis because residues may not evapourate in time

*** More information on the "Verification testing for varroa & trachea mite infestation, resistance and treatment efficacy" can be found at MitGone  ***

 

Oxalic acid

Oxalic acid can be applied by various methods and has become one of the more popular methods for the 'hobbyist' beekeeper and please note:

API-Bioxal, VarroaMed and Oxuvar are the only forms of OA that may legally be applied to hives for the control varroa in the UK

 

Oxalic acid/Glycerin strips

Oxalic acid/Glycerin strips Oxalic acid dissolves to some extent in water, but has a notable fondness for glycerin. This makes food-grade glycerin an attractive carrier for oxalic acid in the hive, especially since its oily nature also confers upon it an affinity for bee (and mite) cuticle.
Practical application: by dissolving oxalic acid into glycerin, and then saturating a cardboard strip with the solution, one can obtain an extended release application method for the acid into the hive, thus continually killing mites over more than one reproductive cycle, thereby overcoming the limitation of the dribble or vaporization application methods.
Click here to download .pdf file of the full details.

 

Application by trickling

See also Archives/Oxalic acid trickle

This method requires a relatively small amount of labour using a syringe.

35g of oxalic acid and 200g sugar are dissolved in 3/4 litre of water, then add more water to make up to ONE LITRE of solution.

Or use the ...calculator

Trickling Oxalic acid

5ml of this solution are trickled into a bee-way of bee occupied comb.

50ml of this solution is required for a strong colony with only 30ml for a weak one.

This method should only be carried out once every year to avoid increased acidity levels in the bees.

Treatment efficacy in broodless colonies is in general more than 95% and is very well tolerated by the bees. It has no effect on varroa mites within the brood cells.

The natural oxalic acid content of honey is not altered by a single treatment with oxalic acid. In beeswax there is no notable risk of residues, because the acids are not fat soluble.

 

Or ...

Trickle VarroaMed
VarroaMed

Application by spraying

For this method a solution of 30g of oxalic acid are dissolved in one litre of water.

3 to 4 ml of the solution are sprayed to each side of the brood frame.

This treatment is well tolerated by the bees but is very time consuming.

Application by vaporisation

1.  Varrox

This equipment consists of a small dish approximately 25mm x 10mm and has two electrical cables attached to it. The small dish is inserted 4 cm into a sealed hive entrance and contains 2g of oxalic acid.

The electrical cables are connected to a 12v battery, the dish heats up and acid vaporises, with the same effect as the vaporisers mentioned below

Varrox

 

2. Isenring's vaporiser

This is a home made equipment and consists of two pieces of bent copper pipe with a block of wood connecting the two pipes. The open ended pipe is inserted into either the sealed entrance or the feed hole in the crown board. Isenring's vaporiser

3g of oxalic acid are feed into the sealed section of the pipe and shaken to the bottom. Both pipes are now connected via the block of wood and the sealed end is heated with a blow torch and the oxalic acid vaporises, passing up into the hive.

 

3.  OR

Roof vaporizer Convert a spare roof and fit a glass window in it. A copper tube fits into the side of the roof and protrudes across the roof's width, having it's underside peeled open to allow the oxalic vapour to escape.
Remove the hive roof and crown board. Place the vaporiser roof over the hive.
roof vaporizer

The open end of the copper tube, outside the roof, has a blanking cap fitted and is filled with 3 grams oxalic acid. This cap is heated with a blow torch and you can observe the oxalic vapour entering the hive.

The vapour condenses within a few minutes in the hive on the bees, honeycomb and stores. Each time the bees move over the condensed material they carry very small quantities of the crystals on their feet. The humidity in the hive makes the oxalic acid active and it corrodes the varroa mite proboscis.

The mites die of starvation after about three days.

The bees are very tolerant to these method:

 

Caution Caution Caution
Oxalic acid is very powerful oxidant and will cause serious injury if handled incorrectly. It must be treated with respect. Wear proper protective clothing and in particular, if vapourising a suitable face mask.

 

 

HappyKeeper varroa floor

Happy-Keeper floor This is a 'new' type of floor board which consists of a wooden frame with a removable centre made of polythene tubes, 3.5mm apart, held together by three struts. It has kept an apiary in Parisian region healthy without any treatment against Varroa mites since the 28th April 1997.

Users also benefit from its other advantages:

More info at www.apiculture.com/happykeeper

Thymol

Apiguard Product name of 'Apiguard' and 'Api-Life VAR' comes in a shallow tray. Peel off the top and place on the top of the brood frame.

Biotechnical methods

Drone trapping

Varroa have a preference for drone brood. By inserting drone foundation and removing sealed drone brood, populations may be kept in check.

Comb trapping

During the summer months varroa spend most of their life cycle within the brood cells. By exercising control over where the queen is laying, it is possible over a period to trap large numbers of varroa within the brood cells. These can be removed for destruction or treatment to destroy the varroa mites.

Dust and Talcs (birds enjoy dust baths)

Dust or powders such as ground pollen, glucose, chalk flour and icing sugars can be used for this purpose. Approximately 50ml applied over the bees on top bars repeated every four days for six applications. mites are not killed and have to be trapped as they fall off and onto the floor.

Nuclei/swarms

In an artificial swarm most mites are likely to be within the cells or on nurse bees taken into split. By manipulation in parent colony, isolate remaining mites on one to two frames, remove and treat or destroy the frames. In new colony during brood stop, may use other control

Brood stop

Exploits the natural death rate of varroa mite by re-queening through de-queening. May include further caging. Summer mites are said to survive from between 1.5 - 3 months.

Biotechnical methods:

Advantages

Disadvantages

  • Do not require the use of chemicals
  • Can be combined with summer management
  • Inexpensive
  • Resistant mites unlikely to develop
  • May not be sufficient if used alone
  • Can be time-consuming
  • Can be complicated
  • Misuse can harm colonies

Chemical treatments:

Advantages

Disadvantages

  • Can be extremely effective
  • Generally quick and easy to use
  • No residues in honey if used correctly
  • Potential residue problems if misused
  • Mites may develop resistance
  • Can be expensive