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Sick Bees Varroa problem – Remedial action for Deformed Wing Virus using OAV

We received a few Emails from folks sharing the news that their Wintering Bees were appearing out the front of the Beehive entrance, with Deformed Wings. Cause = virus – generally caused by Varroa Destructor Mite feeding on Larvae in capped cells.

Here is kiwimana's reply:
I beelieve some remedial action is required right now because…

…..if the girls are new Bees – it might pay to just open a few cappings in the centre of 1x honey frame near brood to see if they feed, new bees find it difficult to open cappings anyway but if they are emerging with DWV – they may not be able to feed at all.

….if there is DWV…. it means the girls are already at high risk – the reasoning ?
because when DWV is already present, its due to Varroa being inside the cells.

Therefore, the brood is already sick inside the cells, this means sick nurse bees are hatching/emerging – plus their first job is Nursing – so they will spread viruses to the new eggs/larvae
Deformities are caused by the Varroa feeding on the larvae after the cell is capped.
The act of feeding off the larvae by Varroa, leads to transference of viruses which in turn – cause the deformities
while Varroa are in cells they are also mating vigorously so inevitably new Varroa, emerge with hatching Bees

Important to share that – Deformed wings are not formed in older already walking worker bees, they will be only housing the viruses in their abdomens – deformities only appear with newly emerging bees.

– we would suggest that you need to treat immediately ! OAV – every 3 days – for 6 weeks.

Why 6 weeks ?

Mainly because your hive is sick.

It will take time for them to recover and your Queen needs to recover also.

So best to assume newer eggs will have viruses already, assume also that emerging varroa are now walking around the hive and hitch-hiking on the nurse bees. While the nurse bees feed the larvae, the Varroa are going into cells and the cycle starts again.

Realistically if you have eggs – its going to be 21 days for them to hatch – its best to assume, they will emerge sick also with viruses.

You really want to get the cover of the OAV in there now,

Benefits ?
OAV – will encourage natural bee cleaning and housekeeping behaviour – with lots of cell-cleaning.

Treating every 3 days will benefit the newer laid eggs which are your new-season bees and you want their cells to be free of Varroa.

So between the 14 to 21 days – you will probably see a large amount of mite-fall as the cells are hatching, you will also see Deformed-wing-bees emerging.

After another 3 weeks – You will expect what outcome ?
….the next hatching of 21 days
– require inspection of Cells there should be no Varroa or minimal
– there should be well-formed Bees emerging
– other deformed wing bees should have died or been removed from the hive

Which means it takes 42 days to recover = 6 weeks

You should see healthy Brood frames and Healthy Queen by week 6.

What Next ?
OAV – treat in 14 days again after inspecting which should reveal:
– new eggs
– improved and fuller laying patterns
– more capped cells
– no deformed wing Bees
perhaps Drone laying starting

After This ?
once you are confident
monitor by oiling your inspection board and checking varroa mite drops weekly.
move to treating fortnightly if you see under 6 mites.
if you see more than 6 mites – treat weekly until levels drop again.

Things you can't control !
The reality is your colonies are at risk all the time as Foraging is where your girls will obviously pick up varroa and rather sadly is that there may be a person around you, who has bees and is not treating at all !
So on-going treatment is generally going to bee more beneficial.

I hope that you find this of help – I think waiting might not be my thought mainly because I have lost hives when I waited to treat, unfortunately the varroa is such a challenging BEAST now compared to even a couple of years ago.



What is OAV ?
OAV means “Oxalic Acid Vaporisation”

How does it work ?
Vaporization is when there is heat-exchange from the vaporizer tool which ‘burns' off the oxalic acid crystals which creates a smoke vapour in the hive.
The smoke vapour is made of small particles which are spread around the hive by movement of the Honey Bees. It is unknown the exact action of the particles but scientists surmise that the particles may paralyse the Varroa Destructor Mite which then cannot feed and it dies. The other particles around the hive are then ‘cleaned-up' by the Bees in their normal behaviour of housekeeping which is all about removing ‘foreign' ‘things' from the hive.

It has been a treatment method used in Canada since 2001.

This treatment method has not been identified as causing any resistance to the Varroa Destructor Mite after 17 years of use, it is described as organic due to the oxalic acid crystals are produced from plant concentrates in the brassica plant family.

What is used in the OAV treatment method:

  • Kiwi Vaporizer
  • Oxalic Acid Crystals
  • Battery
  • Charger
  • Cloths
  • Timer
  • Protective gear including Mask and Gloves

Kiwimana uses OAV regularly, with integrated pest management equipment eg: kiwimana meshboard, sugar shake Jars, Drone management frames.
Meshboard used to check mite fall – weekly / 24 or 48 hours
Sugar Shake jar to check mites on walking Bees
Drone management Frames – added in August ready for Spring wax building
OAV is actioned on a fortnightly basis

Treating when Honey frames on ?
Oxalic acid smoke vapour particles do not appear to flavour the honey, the vapour tends to dissipate so is not intensely concentrated in the honey supers – the more boxes on your hive, the weaker the vapours are. The levels of oxalic acid are not assumed to be of harm to humans however, it is advised that Honey testing is recommended.

OAV does not appear to harm the queen, her laying patterns, walking bees, reproduction of queens, drones, eggs, larvae.

OAV is a legal treatment method in New Zealand.

Disclaimer: kiwimana do not accept liability for the actions taken by person/persons in the use of the OAV treatment method and the tools used in this treatment method, this treatment method is used at the persons own risk – further No liability is accepted directly or
indirectly from its application as conditions of use are outside kiwimana’s control. All safety use advice given when using this treatment method is provided at point of sale.
For point of reference : Material Safety Data Sheet link

Media Credits

Honeybee with Deformed Wing Virus flickr photo by klaas de gelder shared under a Creative Commons (BY-NC) license


Margaret Groot

Margaret is an avid 'Bee Enthusiast' who manages the Apiary, the Bees and their hives, she also provides Beekeeping Services and training for Beeginner Beekeepers.Phew...if that's not enough... she also works in the workshop assembling Beehive products for customers and the Apiary. (and delivers orders as well : )She loves to BLOG and chat about Bees, nature and Beekeeping.
She loves New Zealand native flora and fauna, her fav is the Kowhai...with Manuka honey close second ; )
Some of you may know that Margaret is a qualified Life Coach, she trained through the Coaching Academy in London and holds DipPC.Adv.

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2 thoughts on “Sick Bees Varroa problem – Remedial action for Deformed Wing Virus using OAV

  1. this is a really clear explanation. Very very helpful. Thanks 🙂

  2. OAV method you have set out, I read about on your site last year, I used in June 2017 after finding K wing bees ,white mummies and black mummies in front of the hive, It work out fine you could see the hive recovering each day.

    That hive is still going great, they re Queened them selves in march this year and went into the winter a strong hive with very low mite count.

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