Varroa

Causal agent		Varroa destructor (was Varroa jacobseni)- Parasitic mite
Age group
Egg	Larvae			Pupae	Adult - worker			Drone	Queen
No	No			Yes	Yes			Yes ++	Yes
Clinical signs
		The mites are classically seen in stressed hives in late Autumn
		Drones are preferentially affected as they have a longer pupation and more mated females can be produced
Worker with mite to indicate size						A pupae removed from its cell with a mite on it.
The dorsal surface of the mite						Ventral surface of the mite – note 8 legs – member of the spider family not an insect.
Secondary infections			Colony Collapse Disorder
			Bees infected early in life may have deformed wings – associated with Deformed Wing Virus A number of other viruses are also associated with Varroa infestation.
Infectivity
		The adult female mite infests a larvae as the larvae is about to be capped. The larvae pupates and the mite feeds off the pupae haemolymph. The mite lays eggs. The first egg hatches is a male and the subsequent mites are female. The male mates with his sisters. The adult female mite can live for months when no brood is available to allow multiplication. With brood the life expectancy is 27 days. The Varroa mites can also infest other native bee species – Bumblebees (Bombus pennsylvanicus) for example. However, while they do not multiply on other bees, they can act as a transportation system – horizontal spread
Transmission
		Horizontal - Drifting and robbing. Concentration of hives in an area. Can live on other bees. Vertical –through the brood
Evolution		The Varroa mite appears to have jumped between bee species having originated in Apis cerana. Apis cerana have various adaption’s to manage Varroa. Only the drones are affected. The capping of drone brood is hardened and weak drones are unable to open the cocoon caps and the Varroa die in the capped cell. The workers also seem able to detect the infected pupae and will uncap and remove the infected pupae. Apis cerana also display a range of grooming more intensely than Apis mellifera and are able to remove or damage the mites. In addition they perform a “dance” to call up help from other workers to remove the mites. The combination of these factors enable Apis cerana to remove 98% of mites from their colonies.
Post-mortem Lesions
		Presence of mite
Diagnosis
		Mite seen on the bee
		Monitoring mites with a screened bottom board with a sticky surface – spray on cooking oil for example. When the number of mites exceed 150 in a day – treat.
		Take 500ml of car windscreen washer fluid (alcohol). Shake around 500 bees into the solution (one frame). Shake the fluid and bees. The bees are killed in the fluid. Count the mites which appear. The mites will generally float to the top. If less than 10 then hive infestation acceptable. If more than 40 the hive needs treatment.
		Ether roll – Collect 200-300 bees into a jar and anaesthetise with ether – from an car store used in air to start engines. Use 1-2 second blast. Roll jar for 10 seconds, mites dislodge and adhere to side of jar. Remaining bees can be spread on a white paper to see additional mites if required.
		Icing sugar- Collect 200-300 bees in a jar. Replace the lid with another lid cut with #8 sieve in the top. Introduce a 10g of icing sugar through the sieve. Roll the jar around. Allow the jar to sit for a couple of minutes. Pour the sugar and mites out of the jar through the #8 sieve onto a clean sheet of paper.
Treatment
		None of the treatments achieve elimination only control
Chemical		Tau-Fluvalinate (Apistan) or Flumethrin (Bayvoral) both synthetic pyrethroids Start treatment when sticky boards reveal over 200 mites after 3 days exposure. The strips are normally applied for up to 6 weeks Note these chemicals can build up in the honey and eventually will affect the bees. 2 years of application has affected queen bee fertility. These products may be more useful in the Autumn.
		Apiguard – Thymol. Once the temperature is above 15°C Thymol products can be used. Use two applications 10 to 15 days apart.
		Api Life Var – Thymol, eucalyptus oil, menthol and camphor. This is used two 14 days apart.
		Organophosphates - Coumaphos (Checkmite+).The checkmite+ strip hangs down between frames in the broodnest so bees can walk on it and pick up minute amounts of the active ingredient. Do not put the strip on the bottom board, tops of frames.
		Apiguard in Autumn Varroa control UK					Mite control in Korea
		Be careful when medicating with products that may affect honey quality
		Organic acids treatments are being developed
		Oxalic acid – This is not authorised in the UK. Oxalic acid can kill brood and therefore has to be used in brood-less colonies – in the wintertime. Mix 6% of oxalic acid with 30% sugar solution and apply by the trickling method. Note the products have to be used fresh and breakdown products can be toxic to the bees –hydroxymethylfurfuraldehyde. This product works by damaging the clapses of the proboscis of the Varroa mite.
		Sucrose octanoaten – a sugar and soap solution. Need to repeat 3 times to kill mite eggs.
		Formic acid can be used on the bottom boards. This can be useful to control tracheal mite. Administer 30 mls every week for 3 to 5 applications in the spring. Then again in June. Air temperature needs to be above 22°C but below 30°C
Mechanical		Drone brood sacrifice – drone trapping
		Queen trapping
		Artificial swarm technique
		Shook swarm technique
		Powdered sugar dusting (using icing sugar) – encourages better grooming of the bees. Have sticky paper on the screening board to capture any falling mites. The mites start appearing within 15 minutes of application.
		Screening bottom boards – sticky boards. With a moderate to heavy mite infestation the sticky board will have 150 to 500 mites stuck to it.
		Use more resistant lines of bees –some subspecies have slightly shorter pupation periods which reduce the Varroa population and thus impact.
Others		Reducing drifting
Common differentials
		Braula coeca may resemble Varroa. However, Braula is an insect with 6 legs whereas Varroa as a mite has 8.
Zoonosis		None

Global distribution of Varroasis as of 2010

The global distribution: Positively confirmed countries/areas indicated in red
Life cycle of Varroa

From this a generation time can be calculated:

Time	Event	Time	Event	7.5 days queen would emerge
3 days	Male laid	8 days	Male matures
4.5days	Female laid	12.5 days	Females matures	12 days worker would emerge
6 days	Female laid	13 days	Females matures
7.5 days	Female laid	14.5 days	Females matures	14.5 days drone would emerge
9 days	Female laid	Female not mature in time to be mated

This explains why the queen larvae are rarely infested with Varroa mites, but the longer pupation of the drone allows for large number of mites to reach maturity and fertility.

On average, the female mite produces a new female (as well as herself) for each worker larvae infested and 2 female mites for each drone larvae infested.

Varroa management techniques over the year

Technique	Winter	Spring	Summer	Autumn
Open Mesh Floor sticky paper
Drone brood removal
Drone comb trapping
Apiguard - thymol products
Apistan/Bayvoral – tau-fluvalinate/flumathrin
Checkmite - Coumaphos
Oxalic acid
Icing Sugar Dusting

It is vital to read and follow all manufacture’s advice regarding withdrawal times and bee product sales.

Some of these techniques may not be legal in your area – check with your veterinarian first.

Using drone monitoring to decide on the appropriate level of control required:

	Proportion of intested drone pupae
Spring/Early summer	Less than 2% Less than 1 mite per 50 drones	2-4%	More than 4% More than 1 mite per 25 drones
Summer	Less than 3% Less than 1 mite per 30 drones	3-7%	More than 7% More than 1 mite per 15 drones
Later summer	Less than 5% Less than 1 mite per 20 drones	5-10%	More than 10%
Action suggested:	No action	Light control/plan	Severe risk