Much as I love Rusty’s thoughts and writing, I am going to have to check the reference for this statement:
In both 3-day old and 5-day old larvae, cell death occurred in 25% of the mid-gut epithelial cells after five hours of treatment with oxalic acid
Five hours of treatment? Wow. The approved vaporizing method has never taken more than 5 minutes in my hands. I can’t imagine topping up the iron, or rotating several through the hive for 5 hours! That must put hundreds of grams of the stuff into the hive.
OK, I just read the article. They made a 6.5% solution of OA, and sprayed it directly onto the larvae. They say each larva was given 0.121mg of solution, but it looks like they actually meant 0.121 mg of OA in the solution. That would be about 2 microlitres of the solution they made up. If they mean solution and not OA, that would be about 0.006mg of OA. I don’t know how they could put that little solution accurately onto the larvae. Even 2 microlitres is tough to handle!
If I put 1 gram of OA into my vaporizer, and put that into a single brood box with 8 full frames, it is vaporized over 8 x 7,000 comb cells = 56,000 cells. Assuming it distributes evenly, which is a little unlikely, but I try, each cell would get a dose of 0.018mg. That is only 15% or a little more than one seventh of the amount that the researchers found to be toxic.
I agree we need to be aware, but open-minded too. I routinely visit my hives the day after treatment, and I have never seen bees throwing out young, dead larvae. Maybe there is a difference in exposure to dissolved versus vaporized OA. My guess is that they were trying to reproduce the kind of dosing that would come from an OA trickle.
As far as formic acid toxicity goes, I totally accept that. I have heard numerous accounts of hives doing poorly and queens dying, particularly when it was used on a hot day.
I am still going to treat with OA vapor though. Either that, or my bees will die from DWV - they get symptoms every year.
While we are on this topic, The Bee Informed Partnership sent me a funky behavioral research survey, if anyone wants to do it. It is anonymous, so you can be honest. Odd questions, and some are hard to answer accurately, but I guess that is the nature of behavioral studies:
Thanks for participating in past BIP surveys.
In past survey efforts you let us know if we could contact you if we had other surveys. Well we do!
_We would like to encourage you to complete a short survey developed by collaborators from University of Liege in Belgium. The objective of their study is to better understand beekeepers’ perception of risk regarding Varroa, pesticides, and other factors. The survey also strives to understand how beekeepers make decisions when it comes to adopting or not adopting certain management practices. _
The results will help BIP as it will help us encourage best management practices adoption in US. By taking this survey, you would also support a young scientist’s PhD project!
If you are willing to participate in this survey, please follow this link: http://limesurvey.aesa-epid.be/index.php/677317?lang=en
The survey is composed on 19 questions and takes approximately 15 minutes to fill.
Please don’t hesitate to share this email invitation with other beekeepers.
Thank you for your contribution to research and bee health!
_ Happy New Year, from all of us at the very merry team of BIP_