Bee Informed - Adult bee diseases varroa

1. Adult Bee Diseases Varroa
Varroa; varroosis; varrosis
Pathogen
• Varroa destructor
• Mite stems from Apis cerana
Characteristics
• Imported to Europe around 1980
• Females: button shape, 1,6 mm
• Males: smaller, short lifespan in the brood cell (mating occurs in
the cell)
• 4 pairs of legs
• Moves quickly from bee to bee
Reproduction
• Looks for brood cells for reproduction shortly before capping
• Suck the haemolymph of brood and bees
• Transmits viruses
• In case of heavy infestation there are several mothers per cell
• Preferencefordronebrood
• Mother leaves the brood cell with ca.2 young mites
• Drone brood contains 2 more young mites
• Mother can survive several broods

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Damage of colonies
• Life span of bees reduced
• Entrance gate for viruses
• Increasing load of viruses on colonies
• Leads to colony collapse
• Varrosis with subsequent damages (viruses) is main
Reason for worldwide colony losses
Contamination
• No varroa-free colonies in the EU
• Straying, robbing, transfer
• Colonies collapse
Diagnosis /identification of infestation
• Monitoring of drone brood
• Detection of varroa on the bees
• Krippled, wingless bees > immediate treatment
• Monitoring natural mite infestation > 10 mites/day>
immediate treatment

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Treatment
• Nor survival without treatment
• No treatment during honey flow
• Removing capped drone brood in spring and summer
• Combs to trap varroa
• Interruption of brood
• Form shoots
• Monitoring infestation rate
• Summer treatment after honey harvest
• Winter treatment in the brood-free period
Thymol treatment
– Timing: mid-July, early August at the latest
– Thymol treament: Thymovar or Apilife
– 2 applications
• 1. after honey harvest
• 2. after 3 weeks
• Temperature15 – 30 °c
• Ideal 20-­­25 °c
• 2 sheets per chamber
• 3 half sheet for Dadant
• Ca. 90 % effective
• Long-term effect
• In case of heavy varroa/mite infestation mite fallout > 10/day formic acid
shock treatment required

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Formic acid treatment
• Cauterizationofvarroa
• Partly effective on brood
• High precision and experience required
• Protective measure when handling the acid
• Sponge/flash treatment
– 2ml/comb 60% acid
– 2-­­3 treatments with a 7-day interval
• Evaporator/long-term treatment
– Medicine bottle, evaporator, Nassenheider
– Evaporation principle 10-­­15 ml 60% or 85% acid/day
over 10 days
– Empty space required (reversed feeding tray, super)

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Winter treatment with oxalic acid
• Cauterizationofvarroa
• 3 weeksafterthefirstperiodoffrost
• Spurttreatment
– Applydropsofoxalicacidontothebees
– 18 g oxalic acid/ half a litre sugar water 1:1
– 20-­­40 ml/colonydependingonsize
– One treatment only
• Evaporation
– Evaporationof 2 g oxalic acid with a gas or battery operated evaporator
– Duration ca. 3 minutes
– Close exits for 10 minutes

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Conclusion
• Yearsago,colonieswereabletosurvivewithahigherinfestationrate
• Viruses are an important factor with increasing size
• Through consistent cultivation and timely varroa treatment, the loss can be kept 10%
• Successful beekeeping and harvesting honey is possible thanks to treatments
subsidised by the government
Goal
• Selection of a varroa-tolerant bee in the foreseeable future
Varroa sensitive hygiene (VSH) will be the topic of the 29 March colloquium.
This document was translated thanks to the financial support of natur&ëmwelt - Fondation Hëllef fir
d'Natur.

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Varroa Treatment
In mid-December, 3 weeks after the first frost, the bees should have no more brood. (We can check this
with a thermometer. With no brood we would measure much less than 30° Celsius in the middle of the
cluster.) This is the time when can treat them against the Varroa mites. First we rake-out if necessary the
dead bees from the base plate. We insert a board underneath the hive 3 days before the treatment. The
mites that have died already fall through the grid which is in the base plate. If we count more than 9 mites,
we should treat the colony.
Beekeepers can order oxalic acid when they register their colonies in April. We mix 18 grams into 500 ml
of a mixture of 1:1 sugar and water. It should have about 30° Celsius when we spurt it onto the bees
between the frames. 30 ml for a small - and 50 ml for a normal colony. For the next weeks to come you
will notice the mites on the board that that have been cauterized. This will allow us to start with very few
mites into the next year.
Using a mathematical formula we can calculate the number of varroa in our hives.
http://www.nationalbeeunit.com/public/BeeDiseases/varroaCalculator.cfm
Top Bar Hive Warré and Varroa
In regards to top bar hives (e.g. Warré, Kenyan/horizontal), you may be interested in an alternative view
on Managing Varroa:
“But any treatment of a colony against Varroa merely hinders the long-term co-adaptation of bee and
mite.”
“To treat or not to treat is thus a matter of personal choice. At the time of writing this, most Warré
beekeepers are not treating.”
http://warre.biobees.com/methods.htm
Varroa - Dr.David Heaf on Treatment-Free Beekeeping
https://www.youtube.com/watch?v=6gCY6EZkgxE
Varroa Treatment Discussion at Annual General meeting of the Capellen
Club, 31 January 2015
Annual General meeting of the Capellen Club (Apiculteurs du canton de Capellen, asbl)
31 January 2015 Kleinbettingen
Written by: Kerry Goergen-Todd
Capellen is one of the most active clubs in the country with well over 40 people participating in the
meeting.

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After the introductions, committee re-elections, activity and treasury reports an open discussion was
held on Varroa and the best methods to treat hives.
One method discussed in length was the caging of the queen method – in which the queen is caged with
in small cage built into the middle frame (about 7cm x 8cm). The purpose is to break the brood cycle for
a period of 3 weeks causing the Varroa to drop off. However, several disadvantages of this method
were also discussed, primarily that reintegrating the queen could be difficult, and the colony may well
reject her. A good time and opportunity to replace the queen if needed. Another disadvantage was that
it seemed that Varroa treatment was still needed in most cases after this “caging” causing most of the
participants to ask what the point was then.
Georges Gidt, who has been specialising in Varroa treatments, has tried and tested numerous
treatments. According to him, the best method on the market at the moment is a formic-acid
evaporator (Nassenheider) that gives the best results while being less invasive. The Nassenheider
evaporator has a capacity of up to 290ml meaning it only needs to be filled once.
Jos Guth pointed out that for the Dadant 10 frame 200-220 ml would be sufficient and for the 12 frames
260-280ml would be needed.
A follow-up treatment with oxalic acid at the broodless stage is necessary.
The lengthy discussion proved that many methods have been tried and tested, and trends have been
noted. For example, in one particular year the Varroa plague may be worse in the northern part of the
country and the next year worse in another region, but no one is close to understanding why. One
concern was that immunity against formic-acid will increase if the treatments continue to increase and
that Varroa could thrive once they develop resistance to it.