Varroa Check >Spin-off<

[Ben Framed]

On the topic Varroa Checks, some of us were discussed 3 day treatments with a total of 9. I have a question.
For those of you who do use Oxalic Vapor for treating mites, whether 3 day or other, in conservation intervals, have you noticed any effect on your uncapped brood. If so what are your observation?   

[rast]

I have not and looked today. But my state inspector says in hot weather, she has seen brood removal many times afterward. I have wondered if perhaps it would be extremely hygienic bees that may do it.

[TheHoneyPump]

End of summer and through fall OAV 4 to 5 day intervals here. 6 rounds. Finished last round by September 30. If weather permits there may be a mop-up round done at halloween.
No effect on open brood observed when done properly. Meaning know the limits, stay within it.  Overdose, on a per application basis, can and does kill open larvae. Same goes for dribble.
Have not observed any ambient temperature correlation with OAV or dribble.  Formic by contrast definitely has a strong temperature correlation. Perhaps your inspector is crossed between the two (OA vs Formic). Note that hot weather on its own can kill brood (overheat) and the tossing of brood may have nothing at all to do with the treatment itself.

[rast]

 "Perhaps your inspector is crossed between the two (OA vs Formic)."   No she is not. Discussion was about OA only.

[beesnweeds]

A recent study out of the University of Florida showed no ill effects of increasing from 1 gram to 2 grams of OA per brood box.  They did see an increase in efficacy.  I dont know if they will try and have the label changed to 2 grams or not.  Personally I never witnessed any observable ill effects to brood using 1 gram. 

[Ben Framed]

A recent study out of the University of Florida showed no ill effects of increasing from 1 gram to 2 grams of OA per brood box.  They did see an increase in efficacy.  I dont know if they will try and have the label changed to 2 grams or not.  Personally I never witnessed any observable ill effects to brood using 1 gram.

beesnweeds I feel sure they plan to present the label change request to the EPA. As I received the following correspondence form Cameron Jack April 2020. I do not know if the request has been placed as of yet and if so, if it has been approved.
 
Good morning Phillip,
I don't mind you sharing our conversation on a bee forum. I would say that the current legal limit of vaporizing 1 g is totally worthless. I don't necessarily mean that OA vaporization is a bust, because you start see some control at 2 g and a slightly better effect at 4 g. To be clear though, even after three rounds of treatment at 4 g once per week, we still had average mite loads of about 2 mites/100 bees. We started with high loads, so it did knock it down significantly, but we didn't see the efficacy you would expect from something like amitraz. However, with resistance issues cropping up with amitraz, it is important to have a few more weapons in our arsenal. All that said, I am not recommending anything, just telling you our research findings. As I said earlier, we do plan to take our research to the EPA to advocate for a label change.
 At this time, we are probably still getting our best control with amitraz, though we are starting to have some resistance issues ourselves. Thus, we use OA via trickle and vaporization during the winter and early spring. In Florida we don't have much of a spring and jump quickly into summer, so if we still need a treatment in the spring before the nectar flows, we use thymol.
 We really do try to practice what we preach and we use alcohol washes to sample our apiaries at least every other month to monitor Varroa populations. I feel strongly that frequent monitoring is a critical practice these days, especially after treatment, so you know if what you've applied is even working for you.
Best,Cameron
Cameron Jack, Ph.D.
Lecturer and Distance Education CoordinatorEntomology and Nematology Department
University of Florida
PO Box 110620
1881 Natural Area Drive
Gainesville, FL, 32611