OAG treatment results

 In forskning, metodutveckling, varroabehandling

OAG, OxalicAcidGlycerol is a promising method of treatment against varroa. It fills the need of a method not to stressful to the bees. To handle varroa hidden in the brood as it hatches and you dont want to contaminate coming crop with “hard” chemicals. In the US there is a great need for a treatment that could replace the labor intensive repeated sublimation of oxalic acid. Experiments performed by Randy Oliver has shown that the optimal ratio between Oxalic Acid, OA, and Glycerol is about 1:1 18gOA/14ml Glycerol depending on the absorbing substrate. Where a “dry” loaded substrate is preferred.
In our test we have applied on a paper used for drying plants in herbarium, 0,3 mm thick. We applied about 0,5 g OA per square cm. Maybe the optimal concentration with this type of paper might be somewhat less 0;4-0,3 g/sqcm. Oliver mentions full efficacy may take up to 50 days treatment, but we find it much faster under our circumstances. Actually 50% of the mites that had fallen after 14 days fell during the first 4 days. And on day 13, 98% has dropped compared to the dropping the 14th day.

Detection with BeeScanning

5 colonies. All normal or stronger than normal, colony strength about 14 full Dadant. Nr 29 and 42 strongest. We examined all colonies with beescanning. Only Nr 42 had detectable infestation, about 1-1,5 %. (One mite uncertain).

Treatment

We treated 3 colonies with OAG on top of brood frames. Doses 18 g OA (0,5g/sqcm). Dropping mites counted every 24 hours about 10 AM.


Please notify how bees doesn’t seem to stressed near OAG.

Boards for collection of mites.

Issues

1. Is OAG efficient?

2. What is the relation between the app and the downfall from OAG?

3. Is the app reading reliable for practical use?

Results

1. Very high efficacy 98 %?

2. 1-1,5% is about 200-450 varroa/at colony strengt 20 000-30 000 bees. How many mites were forensic when pictures were taken? During first 4 days fell 800, say average daily hatching is about 100 means. 800 – 4*100 = 400.

3. The app found both the sound colonies and the one in need of care.

Explanation of table

First coloured column E, I and M with sum 8, 16 and 1102 is the the actually counted mites. Total downfall, column F, J and N with sum 11, 27 and 1860 is calculated from (sum/720sqcm area of collecting bottom boards) * 2025sqcm of the whole bottom * % of bottom area under active, brood frames, volume of bees, as seen in the distribution of fallen debris. Agree this is a bit uncertain but from our best judgement)

Conclusions so far

Variation in an apiary may be huge! This may question the thesis about the importance of reinvasion.
With BeeScanning we managed to instantly identify colonies with very low infestation and also in great need of treatment.
OAG is very efficient killing mites. The 14th day fell 2% of what has dropped the previous days. The other way around during the first 13 days fell 98 %. From this colony alone dropped 1 800 mites with 50% dying the first 4 days.

Bees dont seem very stressed by OAG (no scent), especially compared to Thymol or formic acid. Bees chew slowly on the paper. Means will last for long.

Drawbacks

We dont know if OAG in the long term will harm the bees. To be cautious one should of course not treat if no need.
A few dead bees (1-2) has been observed  a few times on top of the bottom board. 14th day after freezing degrees during night, there were some 5-6 cleaned out adult bees on the landing boards. Those were only found at treated colonies. Not at the two untreated.

In nr 42 there also were about 10 undeveloped larvae and deformed pupea, see below. This behaviour showed after 13 days.


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