The old, pre-approval, folk wisdom was four vaporizations, five days apart. That covers a treatment period (from first day to last) of sixteen days, plus any active killing days as a result of the last dose.  This allows for the longer pupal stage of drones, where a large quantity of mites are reproducing.

I dutifully switched over to the three doses on seven day intervals after OAV was approved, which covers just one less day, but I felt it wasn't as  effective as the old-dosing schedule.  So I switched back to doing it the old way.

But the most effective OAV treatments are the broodless-period one-shots in early January in my northern NY climate.  If well-timed (both as to lack of brood, and warm-enough temps for a loose-enough cluster) they will nearly zero-out the mites which has an astounding effect on the mites' return to threshold levels.  That single treatment can buy you six or seven months of not needing any treatment at all.  

In practice, I am not always certain I hit it exactly right, so I often repeat it, trying to refine the definition of the sweet spot.  I have done additional one-shot treatments at various times into Feb., and even March.

Since I run sticky boards every week of the year on every colony, and monthly sugar rolls on each one, I can afford to watch and wait and wait and wait.  

In this atypical weather year, and also partly because of my EFB problems which hammer the mites doubly because of the ensuing lowered brood success, I still have not reached even a 0.25% infestation rate, even on very strong colonies showing no signs of EFB at all.  It seemed so incredible that I finally broke down and tried the alcohol wash techniques I learned from Randy last summer at the NYBeeWellness Conf.  But the alcohol washes confirmed the sugar rolls.  When I first discovered this extremely low level I attributed it solely to the fact that I happened to have been doing sugar rolls on the sickest EFB colonies, with the poorest brood patterns. When I repeated them on apparently unaffected colonies, with excellent brood patterns, I was quite surprised to find the same absurdly low levels.

But it intrigues me because I have never before had such success with my broodless period OAVs. Something (besides the EFB) is different this year.

Was it it the peculiar winter weather pattern, with active foraging for two weeks in Feb., followed by the long, cold, rainy spring? Did that kill off more feral colonies than normal?  Did that affect early season drone brood production rates?

Is it because I have finally made inroads among most of the beekeepers within my foraging area by offering to treat their bees (for free) with my fall and broodless period OAV-ing?

Did the EFB affect enough of my colonies, perhaps with emphasis on certain queenlines (one had 100% illness, one had 0%, two were mixed) that are coincidentally less drone-brood productive, or less mite-receptive, or something?

Did the fire in March which exposed all of them to substantial chemical-laden smoke (killing two outright) leave some protective residue inside the colonies?

I have no idea.

I'm just grateful my long-suffering bees have one less challenge this year.

Nancy

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html