Hello beel
I use a combination of drone removal (in spring), formic acid after last crop in
August or September and lactic acid in November or December. Sorry no experience
with oxalic acid!
I descirbed the method in detail on my homepage (
http://home.t-online.de/home/wolfgang.poehlmann/imkerei.htm) but at the moment
only in german; may bee I can try to translate it in english during christmas
time.
In short: Most of my hives have bottom boards with a mesh. Under this is a from
the backside removable thin board (drawer) from wich the bees are separated by
the mesh. After the last honey was harvested (August or September) I pull the
drawer and put on it a paper as it is used in the kitchen by housewifes (and
men) to clean spilled fluids. Here in Germany a brand is Zewa "wisch und weg".
On this paper I give 25ml of 80% formic acid for hives on one box with 10 frames
Zander (metric Langstroth) and 50 ml for hives on two boxes with 20 frames.
Close the drawer an you are done. You treated for varroa without geting in
contact with a single bee. The dead varroa fall through the mesh on the drawer
an you can see how many you have killed. The advantage of the formic acid is
that it kills mites on bees and in the brood, so you have a fall of dead mites
for roughly 14 days. Normaly I use it one or two times.
In November I remove the drawer and clean it from debris and dead mites. Put it
in for 4 - 8 days and count the dead mites on the board. You made a diagnosis
without bothering your bees. If you only see dark brown mites and no white or
light brown ones then the bees have no more brood. A mite drop of 2 - 3 per week
is ok and no further treatment is needed (one dropped mite per day means
roughly 250 mites in the colony). If it is more, then I use lactic acid in the
broodless colonies. Open the hive when it is over 0 C and not more than +8 C.
The bees cluster relativ tight on 5 - 6 frames. Aplly 20% lactic acid with a
simple mechanical sprayer (2$) on all bees by pulling each bee covered frame and
pressing 3 - 5 times depending on amount of bees. Dont make the bees so wet that
they get black! If the natural mite drop after the treatment is to high, repeat
it until it is ok. Normal is one or two applications. I used lactic acid in one
of my beeyards just this morning.
I applied this method since 4 or 5 years. What I think is important in fighting
varroa is to use not just one method, but several. No matter what method you use
(formic, lactic, oxalic, apistan, bayvarol, perizin, thymol, etheric or
mineralic oils, thermal, drone removal, making splits or what ever) the
efficieny of your treatment may vary. So it is more safe to combine several
methods.
Also diagnosis on each hive (if time permits) or on some hives is important to
monitor the varroa populations, that can be very different from year to year.
I am new on beel. I am a hobby beekeeper with 12 hives in southern Germany,
close to Stuttgart.
Wolfgang Poehlmann
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