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 •  Preference for drone brood •  Mother leaves the brood cell with ca.2 young mites •  Drone brood contains 2 more young mites •  Mother can survive several broods

[Type text]

2

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

[Type text]

3

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 •  Temperature 15 – 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

Bee Together beetogetherlux@gmail.com

4

Formic acid treatment

•  Cauterization of varroa

•  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)

Bee Together beetogetherlux@gmail.com

5

Winter treatment with oxalic acid

•  Cauterization of varroa

•  3 weeks after the first period of frost

•  Spurt treatment –  Apply drops of oxalic acid onto the bees

–  18 g oxalic acid/ half a litre sugar water 1:1

–  20-­­40 ml/colony depending on size

–  One treatment only

•  Evaporation –  Evaporation of 2 g oxalic acid with a gas or battery operated evaporator

–  Duration ca. 3 minutes

–  Close exits for 10 minutes

Bee Together beetogetherlux@gmail.com

6

Conclusion •  Years ago, colonies were able to survive with a higher infestation rate

•  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.

Bee Together beetogetherlux@gmail.com

7

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.

Bee Together beetogetherlux@gmail.com

8

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.