Peter Edwards wrote:

> That seems to be the convential wisdom, but I have dripped oxalic
> (3.5%, 5ml
> per seam) twice at an interval of two weeks with no apparent ill effect.

This is not a comment about Peter's observations, just that his is only
one data point, and there is a lot out there that indicates otherwise.

http://www.apis.admin.ch/host/doc/pdfvarroa/York/Charriere.pdf

The link is to one of many studies (I picked it at random from a quick
google search) that say the same thing, that multiple OA drips are
harmful to the bees. The studies also mirror what continental beekeepers
have observed and posted here.

The main problem with OA is treating when the colony is broodless,
something easily done in northern cold climates but not in warmer
southern climates. If you do it when the colony is broodless, you
effectively kill nearly all Varroa, or over 95% as a minimum. OA can be
applied down to freezing, so the colony is usually broodless (in
November in Maine. Still fairly tropical,  40sF in the day and 30s at
night.).

I have heard of multiple applications made here in Maine, but usually by
those who had no choice because of high Varroa loads and no broodless
period (summer). Problem with a report of no harm from them is how do
you tell what killed off the colony, PMS or OA? Or if they even noticed
a decrease in bees if it survived? If it was noticed, I am sure Varroa
would get the blame.

Which brings me back to a favorite topic. Unless you are conducting a
controlled study, I know of few beekeepers, no matter how experienced,
who can tell that 10-20% (or even more!) of their bees died during a
short period in the summer when you have brood being raised at the same
time. I know I am one of those. When you have wall to wall bees and
brood, you can lose a lot of bees and not even have it register since
new bees replace them.

Winter is where the real effect comes in, because then there is no brood
to replace those dead bees. Then you will see a difference in spring.

Part 2 of one of my favorite topics- if the beekeeper's practice yields
20-40% unnecessary bee deaths over the winter and they have been doing
the same thing forever, they will never know it since they treat all
their bees the same improper way and get the same small number of
survivors every spring. Hence, they will defend their practice as having
no effect since they see none. And blame their location for poor honey
crops.

Bill Truesdell (This post has been checked for unnecessary quotes and
has been approved by the Board of Unnecessary Quotes (BOUNQ- almost
pronounced bounce, the action of the Board to UNQ), Allen Dick, Chair
emeritus)
Bath, Maine

-- Visit www.honeybeeworld.com/bee-l for rules, FAQ and  other info ---