Allen dick wrote
> Aren't we all?  Chemical residues are definitely something to be worried
> about.   I understand that oxalic and formic do not leave noticeable
> residues, but I had heard that thymol can get into honey enough to be
> tasted?  Have you observed that?
>
> Have these treatments affected your honey yields or wintering at all, or
> have you studied that aspect of this approach?

From my experience I would say that everything we use for varroa treatments ends up in small amounts sooner or later  to honey.  Formic acid treatments raise the amount of it in the honey. From Central European results we know that the natural amounts of  formic acid are very high in some honeydew honeys and the varroa treatments don't raise the  amount of formic acid even near these natural figures.

Oxalic acid has not had so many residue studies, but we can say that the residues are very small.

Thymol was a problem in the beginning in Switzerland and Germany when beekeepers just poured chrystals into hives. About the same way as menthol is used in the USA. If you have thymol treatment in the hive during the honeyflow you can get residues that you can taste.  We only recommend to use it in the fall once for about 3 weeks or whatever it takes to evaporate. We simply melt the thymol in water bath and pour 12 g for 5 cm *15 cm wettex ( a commercial kitchen cleaning cloth). One strip for hives with one box and two for a hive with 2 boxes.
Even this kind of short use leaves some residues ( from last summer we could detect residues in about 50 % of samples) but these are about 1 % from the level detected by human senses. The residues don't increase from year to year as they do with synthetic chemicals.
Thymol is used in some sweets and soft drinks.  Its also the main component of Apilife VAR varroa treatment.

As I told before all these three are also natural ingredients of  honey.

Overdoses kill bees, but when used according to recomendations we have had very  few problems. Thats why we have had the normal beekeepers to accept so widely this way of varroa treatment.

Ari

Ari Seppälä   MMM
Projektipäällikkö  Project Manager
Suomen Mehiläishoitajain Liitto r.y.
Finnish Beekeepers' Association
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