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Opinions on oxalic and mineral oil fogging for varroa?


#1

So at the local meeting last night they had an “ask the expert” presentation. Most of the questions and answers revolved around dealing with varroa. Apparently it is a massive problem here in the dessert. Several treatments were suggested, “grease patty”, oxalic acid vapor, and food grade mineral oil fogging.

Can I get some “second opinions” on which of these is the most effective/necessary/useful? No one in the club is vocally or outwardly doing treatment free which would be my preference but I am starting to think it might not be possible here.


#2

Once varroa is present you will never rid the colony entirely. The best you can aim for is to keep the levels tolerable so that they don’t damage the colony.
It is possible to go treatment-free but that is an entirely separate consideration.
It’s important to understand how and when varroa levels are important. The single most crucial treatment, in my opinion, is in late summer/autumn after you have taken the honey for the last time and before winter bees are made (these are the ones that will take your colony through to spring).
They need to be as healthy as possible; they have a long time to live and much work to do when brooding starts anew.
After harvest is when the brood nest contracts and there comes a time when varroa will outbreed bees. You need to take action then.
There is a choice of using Thymol/Formic acid/Oxalic acid as the “non chemical soft options” or going for pesticides.
I personally fog oxalic after harvest. You don’t need the colony to be brood-less for oxalic to work. You just have to repeat the process every five days for three treatments. I fog from under the mesh floor from the back of the hive. The bees hardly notice.
Most people who use thymol or formic (MAQS, say) will dribble oxalic on the cluster mid winter. I personally think that if your autumn treatment was effective, this is unnecessary.
When the colony starts making drones I uncap a few to see the level of infestation and put in a short frame if there is a problem. The bees make drones which will take most of the varroa and you can cut it off after capping.
Artificial swarming will create a brood-less period further slowing varroa build up.
There are other methods of trapping the queen and sacrificing newly laid brood to remove varroa.

PS treatment free options include removing drone brood as explained above, letting the bees build their own comb. Some bees exhibit hygienic traits and have high levels of DWV type B which is asymptomatic and displaces the harmful type A which causes deformed wings. These bees seem to cope somehow on their own. Personally I don’t think you can go treatment free unless you are lucky enough to have this scenario or breed for it.


#3

Dee is correct; Oxalic acid vapor kills phoretic mites only hence the treatment every week for about 3-4 weeks, at least here in the USA. Basic bee biology tells you that when the broodnest starts to get smaller to prepare for winter the mites are at a peak.


#4

Gee I don’t know. I find that once the beetles get into the dessert all the honey in the world doesn’t help!


#5

This from BIBBA is interesting
The most urgent problem in apiculture, not only in Britain and Ireland but throughout the world, is that of protecting the Western honey bee against extermination by the varroa mite. The initial preferred treatments were products containing synthetic pyrethroids, but after a time there quickly appeared pyrethroid resistant varroa. Softer substances such as thymol were used, but these needed the support of IPM techniques and organic acids including oxalic and formic. The ultimate hope is that varroa-resistant strains of bees may evolve, but at best this is likely to be a very long term solution to the problem. If, as is supposed, the separation of the cerana and mellifera species occurred in (relatively) recent times, the gene which enabled cerana to develop a defence against varroa may still be lurking somewhere among the genes of the mellifera races. There is a danger that the development of resistance among apiary stocks might be concealed by the normal anti-varroa treatments and that a resistant strain might be lost through the death of the queens. A case might be made out for encouraging feral colonies in suitable areas. In due course most if not all feral colonies will be wiped out by varroa and the argument that they would act as centres of infection for apiary colonies need scarcely be considered as they would never exist in sufficient numbers to threaten apiary stocks – unless of course a resistant strain evolved in the wild, in which case they might transmit through the drones resistance to the apiary colonies.


#6

So during the main season treatment may not be necessary, it’s mainly as the hive shrinks for winter that treatments are most necessary?

Are there any drawbacks or issues with treating year round?

During the meeting several people talked about having hives abscond and it was theorized that it was because mite counts were too high and bees abandoned the hive because of this.

I’ll ask more at the next meeting but I’m trying to get an idea of an application “calendar” for oxalic acid treatments.


#7

You need to see what the infestation rate is before you put supers on.
If treatment is necessary then I might think about MAQS which is best put on with a super in place so you’re not losing any honey gathering time or space anyway. I personally wouldn’t use MAQS later in the season as it can lead to queen loss at a time when the colony can’t replace her.

This article by Randy Oliver is the bees knees.
http://scientificbeekeeping.com/fighting-varroa-reconnaissance-mite-sampling/
Take your time to read it all, there are a couple of very useful graphs towards the end.


#8

Hi Dee, can you please explain what you mean by putting in a short frame?


#9

I have my bees on 14x12 frames in the brood so I put in a super frame. The bees will make drones which you can then take away and slice off the bottom when it has been capped. Common practice here is to repeat this maybe twice.
I don’t do it much anymore. There are better ways of coping with varroa than sacrificing drones