> Chiesa (1991) was able to control V. jacobsoni in honey bee colonies with 
> thymol without noticeable damage to the colonies at temperatures ranging 
> from 5 to 9 C (41-48 F). However, Gal et al. (1992) found thymol 
> applications deleterious to bees when temperatures reached 27-28 C (80-82 
> F).

I have used thymol crystals at 30C without problems (but not often - 30C is 
unusual here), but it should be remembered that I have fully open mesh 
floors.

With lower temperatures I find that thymol works well in colonies with 
plenty of brood, but is much slower to evaporate (or deliquesce) in colonies 
with little brood.  This is very noticeable with our bees (A.m.m.) as poor 
weather in July can cause queens to go off lay temporarily.  We seem to have 
no problems using thymol on colonies returning from the heather moors in 
September when the weather can be much cooler - these colonies normally 
return with large areas of brood after the stimulation of working heather. 
So in my view it is the warmth from the brood that makes all the difference.

Have researchers considered the varying effects of mesh floors, amount of 
brood and the sub-species of bee?

Best wishes

Peter 

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