Is Oxalic Acid vaporization temperature dependent?

[snl]

For those who vaporize using oxalic acid, is there an optimum outside temp range? Best times of day to use?


Thanks!

[westernbeekeeper]

I'm interested in this question too. I am also wondering where you can purchase this treatment.

[jean-marc]

Cool temperatures, just above freezing when bees are clustered and broodless (4 or 5 degrees Celcius). So for those that are further north late october , kinda before the snow flies. It's used a a cleanup treatment, after you used either formic acid or thymol. Those treatments are pretty good but not 98% or more effective, so the oxalic sublimation is used to get the last of the varroa. Colonies should be broodless or as close as you think you'll get for best results.

Work in the daytime so you can see what you are doing.

Jean-Marc

[snl]

JM......

I'm directing this to those that use OA as the main treatment, not a cleanup. Thanks!

[WWW]

snl, I have started my sublimation treatment this weekend and will treat two more times in the next two weekends to cover the 21 day brood cycle. To answer your question I like to treat in the early morning hours when most of the bees are still in the hive and I like the temperature to be above 50 deg so that the bees are not starting to cluster and will circulate the vapor by fanning. The temperature here was 60 deg this morning. I do not know if there is a maximum temperature limit with Oxalic vapor. Where I live here in Southeastern Ohio we like to treat our hives as soon as the supers are pulled in the fall, and that is around the end of August to the beginning of September time frame. The reason for this is to allow the bees time to raise another batch or two of brood before winter so the colony will go into winter with a good amount of healthy young bees.

Westernbeekeeper, Oxalic acid can be purchased through Amazon or Ebay and it is possible to find it sold as wood bleach at local paint stores or lumber yards.

http://www.ebay.com/itm/12OZ-WOOD-BL...item5ae5c8ef53

[johng]

No it is not temp. dependent. But, you have to understand the limitations of Oxalic acid vapor. I think this is what Jean-marc was trying to say. It will only kill the mites that are on the bees at the time of the treatment. Most of the mites are in the brood cells at any given time if brood is present. So you have to treat during a brood less period or you have to do multiple treatments a week or so apart. You can't just treat one time as a main treatment and expect it to work.

[AmericasBeekeeper]

Interesting, this study says there is a direct correlation of temperature and humidity. Remember vapor pressure is relative to temperature times humidity times a coefficient for the compound. When either goes up the vapor pressure goes up. The only conclusion I could determine with certainty is that oxalic is ineffective. http://www.medwelljournals.com/fullt...a.2011.802.805
University of Nebraska - Lincoln says it is good on package bees, temperature and humidity effect results but did not test either parameter digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1186...

[crofter]

A clip from that study ("The efficacy of oxalic acid was not effective alone to control varroa destructor. Neither oxalic acid with trickle, oxalic acid with vermiculite nor oxalic acid with in dust was significantly different. The result of oxalic acid treatments investigated in previous experiments was also evident in the studies" (Gregorc and Planinc, 2001; Brodsgaard et al., 1999).
This suggests that the heat vaporization method was not used on the oxalic treatment so that should be considered in assessing its effectiveness.

The thread post asks if the vaporization temperature is critical; to me this might not be referring to the weather conditions. I think the ideal temperature applied to the crystals should be in the neighborhood of 315 deg. F.
Since as noted it does not get under the cappings where 80% or more of the mites are, multiple treatments are needed to also pick off the emerging mites before they can re-enter cells.