So I know this is a very late follow up but I thought it may be helpful for me to review my own actions and this may bee helpful for some other newish bee keepers. The short book is both of my remaining hives are doing well, and one is doing extremely well BUT 6 weeks after treatment with Oxalic Acid sublimation I am reaching levels where I need to treat again. Hive #1 had 6 varoa in a half cup of bees using the sugar roll method and Hive #2 had 12 varroa. Now hive #2 is very rapidly expanding so I would expect more varoa.

Hey Richard,

Happy to hear about your gangbusters hive.

What's the mite load after the three OA treatments?

I agree with you on the solid sugar patties.  When there are other food sources, they tend to ignore them, however, as an emergency feeding in winter, I've found frequently they work.

Have you been seeing any drones yet?

Allen Engle

Richard, Here is my two cents worth.  What I am about to write applies mostly to Langstroth hives. Ware, top bar, or long hives may require a little more creativity to use an Oxalic acid vaporizer.

  Oxalic acid is used in the midwinter time slot because most hives in colder climates (I think we qualify) have very little to no brood then. And, the treatment does not require the hive to be opened other than possibly temporarily enlarging the entrance a bit if you have made it very small for the winter.  Most discussions I've seen say that the brood-less (or low brood) period is late December or early January. As you suggested, that would mean that the mites are therefore riding on an adult bee and exposed to the vapor. Not protected in a sealed brood cell.  I (actually a friend cause I'm recovering from surgery) treated several of my hives this winter on February 3rd with vaporized oxalic acid. Even February 3rd might be a little late for getting the most effect from the treatment.  That doesn't mean that a treatment won't help. I had the hives treated that had higher mite counts prior to treatment with Formic Acid in August.  I figured they would benefit the most because they seem to have the least natural resistance.  I will do a mite count in March or April when the weather is warmer and we will see how things look then.

Good question Clyde. My thinking was this. As Oxalic Acid is only affective on hatched bees (not on Brood), then an early application when the hive is essentially bloodless will be the most effective, this is also supported by most of the reading that I have done. In reading around the net (I know, that is not always a reliable source of information), there has not been a resistance to OA treatment with many years/decades of use in Europe and other countries (yet). This would be more of a prophylactic treatment to help start off the bees season in a nearly mite free state. Last year it seamed to work well but I did not do a side by side comparison of early treatment and not as I only had 3 hives. Much of the reading that I have done does indicate a late fall or winter treatment is very effective and that summer OX treatment is less so due to presence of brood. so, One treatment now or a succession of treatments later in the summer when there is brood present, or using Apivar or one of the other chemicals which I do not like to use in my hives.

I was putting this question out there to hopefully start a discussion to get more information for myself and other back yard beekeepers so thanks for the reply and please keep it coming.

And, no, if there were still snow and cold weather in Bend I wouldn't be thinking of this but it has been warming up lately (very early) and the girls are flying and so I'm trying to get ahead of the season. I'm hoping my bees don't just burn through their available food supplies before spring actually arrives and nectar and pollen are around so I am starting to use sugar patties and some frames of honey saved from last year and the girls are going through it for sure.

Again, thanks for the reply.

Hey all, I was just wondering if during this unseasonably warm weather here in Central Oregon if it would be to early to do an Oxalic Acid sublimation to treat for Varroa? I am under the impression that it is not to early and intend to do a treatment on my 2 surviving hives on the next day it cracks over 50 degrees.

Last year I did an OA sublimation during a similar early season warm spell and I had very low mite counts throughout the summer so I'm personally under the impression that it is a good idea but are there any reasons not to???

So Far, 2 of 3 hives are still going strong, plenty of bees and good food stores. The one hive which has not survived was my weakest going into the winter and I think they just starved out. There was still honey in the edges of many frames and a couple of nearly full frames but not right where the main body of bees was (Damn!).