Evaluating the Efficacy of Oxalic Acid Vaporization

[Walrus]

New research published:
https://www.ncbi.nlm.nih.gov/pubmed/31909423

Evaluating the Efficacy of Oxalic Acid Vaporization and Brood Interruption in Controlling the Honey Bee Pest Varroa destructor (Acari: Varroidae)
Cameron J. Jack,1,3, Edzard van Santen,2 and James D. Ellis1

Abstract:
A successful Integrated Pest Management approach to Varroa destructor Anderson and Trueman control in managed colonies of western honey bees Apis mellifera Linnaeus (Hymenoptera: Apidae) must be an improvement over conventional control methods and include cost-effective treatments that can be readily employed by beekeepers. Herein, we tested the efficacy of oxalic acid (OA) vaporization and brood interruption as Varroa controls. Sixty experimental colonies were randomly assigned to one of six treatment groups with 10 colonies per group. The six treatments were: 1) OA applied once, 2) OA applied three times, 3) brood interruption, 4) OA applied once + brood interruption, 5) OA applied three times + brood interruption, and 6) no OA or brood interruption. The OA was applied via vaporization, with each application being 1 g OA applied through the hive entrance (label rate), on the bottom board. Brood interruption was accomplished by caging a colony's queen in a queen cage for a period of 24 d. An additional 10 colonies were treated with amitraz (Apivar - positive control). Varroa levels were estimated before, during, and after treatment applications using sticky boards left in colonies for 3 d. Our data suggest that queen caging to achieve brood interruption during the fall season can negatively impact colony strength and survival. We observed high colony mortality in some treatments, despite diligent colony management to alleviate the side effects of the treatments. Colonies treated with amitraz were healthier and had better survival than those treated with OA vaporization. In conclusion, OA and/or brood interruption did not provide sufficient Varroa control.

The "forced brood break" didn't work out very well, and an OA dose of 1g per brood box (Lang) was not enough according to this. The experiment was in very different conditions to here in the UK. There are problems with it, as there often are, but at least they tried. It seems to me that measuring mite falls is not necessarily the same as measuring mite loads.

There has been discussion elsewhere about how to consistently ensure a known dose of OA by sublimation, because it can break down into formic acid, carbon dioxide & carbon monoxide at higher temps.

It makes the case for testing varroa levels with alcohol wash or sugar shake all the more compelling IMO.

 

[SDM]

Breakdown to formic acid etc isnt an issue at all imo.
And i cant see why they tested such a small dose of oxalic acid when other studies have identified a far larger dose as both harmless to bees and optimal for mite control . All in all it looks like a study designed to fail.
Thats just an initial thought , I'll read it properly now.

 

[domino]

I've just read this paper. This is the mite levels.

This is the regime

OA is delivered every eight days, which I assume is because they cage the queen day one and release her day 24 for the full brood break.

This technique is almost as good as the Amitraz control, my key takeaway is their comments about the amount of OA to use.I@ll be using 2g even per box from now on.

 

[domino]

Breakdown to formic acid etc isnt an issue at all imo.
And i cant see why they tested such a small dose of oxalic acid when other studies have identified a far larger dose as both harmless to bees and optimal for mite control . All in all it looks like a study designed to fail.
Thats just an initial thought , I'll read it properly now.

Because that's the number they got from published studies

 

[SDM]

Because that's the number they got from published studies

I haven't seen the full study , but assuming they were using langstroth deeps, the published studies indicate at least 2g per treatment .

 

[Dariusz]

Im newbie but from this type of test,stinks away monopolistic advert.
looks especially for purpose dozing such small amount of OA compared to amitraz.
because OA 2.5gr and above per hive its very effective and not showing side effects,like for example amitraz where just touch too much and problem all ready.

 

[Walrus]

"We used the commercially available Varrox-Vaporizer (OxaVap LLC, Manning, SC) apparatus to vaporize 1 g of OA dihydrate (Sigma Aldrich, St. Louis, MO) per brood chamber, per label instructions."

They tested with 1g per brood box according to the label instructions. Shame they didn't also try 2g or 3g as well, but maybe they were obliged to follow the instructions

 

[Newbeeneil]

They tested with 1g per brood box according to the label instructions. Shame they didn't also try 2g or 3g as well, but maybe they were obliged to follow the instructions

Couldn't have been male if they followed instructions

 

[charlievictorbravo]

"If all else fails, read the instructions"

or

"Instructions are what you use to find out what you did wrong."

Incidentally, I have not read the paper yet but to save me time, did they comment at all on the exact way that vaporised OA kills Varroa mites. The assumption has always been that the acid burns either the soft tissue foot pads or the soft mouth parts but it would be helpful to have this confirmed and that the OA is not actually poisoning them.

CVB

 

[SDM]

Im newbie but from this type of test,stinks away monopolistic advert.
looks especially for purpose dozing such small amount of OA compared to amitraz.
because OA 2.5gr and above per hive its very effective and not showing side effects,like for example amitraz where just touch too much and problem all ready.

From the abstract it does look like a study designed to promote amitraz but having read the whole thing( thanks Steve), amitraz is criticised for resistance issues.
I still think the study was loaded, but loaded to highlight the inadequate dosage of oxalic vapour allowed in the US.

 

[domino]

From the abstract it does look like a study designed to promote amitraz but having read the whole thing( thanks Steve), amitraz is criticised for resistance issues.
I still think the study was loaded, but loaded to highlight the inadequate dosage of oxalic vapour allowed in the US.

They had two controls amitraz and nothing. Reading the study I don't think it was either designed to fail or to promote anything. It was designed to test what happens if you cage a queen and treat with oxalic.

In their discussion, they even say that the literature around the most effective oxalic treatment is lacking or largely unpublished.

 

[SDM]

Designed to test what happens with a dose believed to be inadequate for the hive type.

 

[madasafish]

If this study is typical of US practise, I now understand why US losses are so high.

 

[Erichalfbee]

Designed to test what happens with a dose believed to be inadequate for the hive type.

Looks like it doesn’t it?
My nucs get 1g the 14x12s get 3g all delivered above the omf by sublimox.

 

[SDM]

Looks like it doesn’t it?
My nucs get 1g the 14x12s get 3g all delivered above the omf by sublimox.

Yes, and in that sense it's an important study despite the results being predictable. The USDA or whoever licensed oxalic at 1g needs a slap to wake them up to the opportunity their making their beekeepers miss out on. Mind you, that's a bit rich coming from us, at least they had the sense to license pure oxalic instead of selling the rights to someone to print money while making an inferior product.