The Ulster Varroa Guidance Page

Monitoring and Control of Varroa Destructor   

Essential publications: ‘Managing Varroa’ and ‘Varroa jacobsoni: monitoring and forecasting
mite populations within honey bee colonies in Britain’ both published by MAFF (now DEFRA).
For web site see below at National Bee Unit.

The aim of the Ulster Beekeepers Association is to have an integrated pest management
method adopted by all our Associations, since, in time, Varroa destructor may become
resistant to the varroacides mentioned below. They should be used as infrequently as
possible to prevent the build up of such resistance, but always at the full recommended
dosage and for the recommended exposure period.

The purpose of this document from the Ulster Beekeepers’ Association is to give
members the information to enable them to control Varroa destructor with the use
of as few varroacides as possible and so prevent a build up of such resistance, as
mentioned above, for as long as is possible. The use of a broad spectrum of treatments
is known as an Integrated Pest Management (IPM) programme

 It is essential that bee colonies are monitored for levels of Varroa destructor

(i)                  before the confirmation of the discovery of varroa and

(ii)                after the confirmation so that varroa levels can be controlled when necessary.

  Monitoring.

(i) by natural daily mite drop

(ii) mite drop resulting from the use of Bayvarol or Apistan strips (for use see below)

(iii) by drone uncapping.

Methods (i) and (ii) require either varroa floors with an insert or open mesh floors
with a removable tray and disposable card or paper insert.

Method (i).The insert is left in for a number of days (preferably 5 to 7 for natural mite
drop), removed and the number of mites counted. The daily mite drop can then be
calculated, see below(the natural mite fall only).

Method (ii). If it is suspected that the varroa mite is present, Bayvarol or Apistan
strips are inserted for 24 hours, when the mite fall should be easily spotted if Varroa
destructor is present. (Supers must be removed). The strips are removed after the
testing period.

Method (iii). If using drone uncapping, at least 100 drone cells should be uncapped.

Every colony in the apiary must be monitored.

Monitoring should be in Spring and Autumn before Varroa destructor is discovered and
in Spring, Summer and Autumn after discovery (see summary).

The number of mites in the colony can be calculated using

(a)    the ‘Varroa jacobsoni: monitoring and forecasting mite populations………’
 (see above)

(b)   the website www.nationalbeeunit.com (click on ‘Varroa model and calculator’
in index, then on ‘Varroa calculator’)

(c)   Commercial Software

Control/treatment is recommended when certain levels of mite specified in the calculators
above are reached.

Control Methods.

No control is required if Varroa destructor is not found in the apiary but keep monitoring.

If varroa is found, the Quality Assurance Branch, Room 1019, Dundonald House,
Upper Newtownards Road, Belfast BT4 3SB, telephone number 02890 525001, must be
notified. The Bee Disease Control Order 1998 states that Varroosis is a notifiable
disease and that it is a legal requirement to notify DARD immediately infestation is
discovered. Treatment will be recommended by DARD and will be carried out
under the supervision or instruction of DARD.

Once the initial treatment has been carried out under the supervision of DARD, monitoring
must be continued and must form an integral part of the management programme of the
bee-keeper.

Control methods will depend upon the season of the year. Varroacides such as Bayvarol
and Apistan should not be used if honey supers are on hives. If the infestation is severe
supers may be cleared and removed for the duration of the treatment

These treatments must be used in accordance with the instructions on the packet and
must be removed after 6 weeks.

With the advent of mites resistant to Apistan™ and Bayvarol™ in England, Scotland and
Wales, we must be on the alert for their appearance in Northern Ireland. A method for
checking for resistant mites is given by the National Bee Unit in their web
site at www.nationalbeeunit.com.  The Central Science Laboratory, to which a link is
provided on the UBKA web site, also provides information in their documentation.

In addition, local bee inspectors will take random samples during the year.

If such resistant mites are discovered, please report the fact to your local Association
and to DARD.

An integrated pest management (IPM) programme will include, in addition to the
chemicals already mentioned, the following:

Open mesh floors.

A certain number of live varroa mites will fall from the colony, drop through the mesh
and be unable to return to the colony. Open mesh floors can be used all year round.
Figures suggest that  20% of mites can be lost in this way.

Sacrificial drone method.

The beekeeper can begin to use this method once a colony begins to rear drones
and when there is a reasonable nectar flow. It involves putting either a shallow (super)
frame, with drawn comb in it, or a brood frame with a 2.5cm deep starter strip of comb,
in the centre of the brood nest. The bees will construct drone comb below the existing
comb. Once the queen has laid this up and the cells are sealed, remove the frame, cut the
drone brood off and destroy it away from the apiary. The frame can then be replaced
in the colony and the process repeated.

Artificial swarm method

If, on monitoring, a large population of mite is discovered in the middle of the honey season,
the artificial swarm method can be used to reduce the number of mites and prevent
collapse of the colony. For more details see ‘Managing Varroa’ page 8.

Use of thymol, an essential oil.

The simplest method of administering thymol is to use Apiguard, following the instructions
on the packaging. Apiguard contains thymol which will leave a residue in wax and must
be used only when the honey crop has been removed.

Formic acid (unlicenced in UK)

This can be used in August and September, at temperatures in excess of 10°C, but
as a corrosive acid must be handled with care. The molecules of formic acid can enter
the cells through the cappings and destroy mites before they emerge. 20-30ml of 85%
formic acid is administered on an absorbent pad which can be placed on the mesh screen
below the brood chamber, keeping it away from the bees. If used above the colony
20-30 ml of 60% acid is used. These figures are based on research by the Swiss Bee
Research Centre. Because of the dangers to operatives (note strength of acid
used), this method is not recommended by UBKA.

Oxalic acid (unlicenced in UK but under review)

Oxalic acid can be used when there is no or little brood present but again must be
handled with great care. It also may leave residues in wax.

The trickle method described below can be used only once in a colony.

A 3.5% aqueous solution of oxalic acid, 5-6 ml per frame occupied by the
cluster, is administered, via a 100ml syringe to provide as many small droplets as possible,
over the occupied frames. (See Belfast Beekeepers web site for oxalic acid premade solution)

NB the use of any acids (including lactic acid) poses dangers to those who handle
them. Gloves and a special mask must be worn and the acids should be
diluted/decanted etc in a well ventilated area.

Each individual beekeeper should make his own risk assessment and adapt his
practices to ensure his own safety and that of others. If in any doubt consult,
Health and Safety regulations.

UBKA would strongly recommend that all beekeepers in an area would arrange to treat
for Varroa destructor at roughly the same time to decrease the likelihood of re-infestation.

Summary

Treat only when necessary.

Useful contact for further details: National Bee Unit, 

Updated : 21-Feb-2008