Subject: Varroa control by Formic-acid

From: Ulli Hoeger <[email-masked]>
Date: 11 Jun 1996 15:02:30 GMT

Maybe some of you are interested in an alternative way of Varroa 
control.  I hope that the main manuscript will be transfered to 
this newsgroup too.

Formic-acid (Formiat) for Varroa control

All the chemicals offered by the pharmacological industry for Varroa 
control
cause 2 main problems:
-The mites become resistant to the substances after some years, 
 new substances needed in future
-All these substances make residues in bees wax and honey, 
 not very good arguments for our business
Organic acids like Formic-acid make not such problems.  Formic acid is 
part of the honey and it is reduced in short time by honey enzymes and 
oxidation.
Different ways of Formic acid application for Varroa control were tested by 
german
beekeepers and research institutes in the past.  One method, successfully 
used by 
myself and many other beekeepers in the last 4 years is described in the 
following manuscript.  
I would like to thank Ian, a british beekeeper who point out that there 
might be somebody else interested in a alternative way of Varroa control, 
and so I decide to post the following.

Formic acid for Varroa control,  Kraemers way!

The Kraemer-Platte is a way of applying formic-acid for Varroa control. 
This
treatment has been used successfully for several years by many german
beekeepers.  It requires for each hive one Kraemer-plate, an empty super, 2
small wooden frames (comb-frames), and some old newspapers for isolation. 
These
methods may only be suitable for beekeepers with a small number of hives.

Mr. Kraemer is a german beekeeper (an Imkermeister [Master Beekeeper]), who
spent a lot of time and money to work out his way of Varroa-control when 
the
mite became a problem in Germany about 20 years ago.  I would like to thank 
him
for his work, which gives us an alternative way of residue-free Varroa-
control.

Building a Kraemer-Platte:
Material: The plate body is made from Weichfaserdaemmplatte 10mm thick 
(this
material is made from wood and usually used for insulation inside houses 
and
sometimes also in the lids of hives, it seems a little bit like fibrous
cardboard; make sure to get insecticide free material WITHOUT bitumen on 
one
side).

Plate-size: 247mm x 170mm x 10mm

Pack the plate in a foil-bag (size 210mm x 300mm) of acid resistant 
plastic-foil. 
Fill each plate with 250ml (298g) of 85% formic-acid (use a syringe and 
wear
gloves and eyeshield for protection; formic acid is a very strong acid!), 
and
weld the bag with a double seam.

The price for such a plate should be less than 5 US$ if a number of plates 
are manufactured (Mr Kraemer sold these prepared plates for 6 DM each in
the past).

Fall-Application

Work to do before the Kraemer-Platte is placed in the hive:
Weigh the filled Kraemer-Platte and note the weight.  Perforate BOTH sides 
of the foil-bag with the necessary number of holes (diameter 15mm, use a 
metal
tube with sharp edge). The number of holes depends of the size of the hive.

                                 Number of holes on EACH side of the foil-
bag
                              1 brood-camber/hive                2 
brood/hive
number of combs             6-8     9-11     12-15     16-19             
20-24

Freudenstein-size(180x318)   8       9         10       -                -
Normal-size(202mmx350mm)     9      11         12       14               15
Zander-size(195mmx390mm)    10      12         13       15               17
Langstroth(200mmx420mm)     11      12         14       17               19
Dadant-size (275mmx410mm)   12      13         15       18             -

Place the perforated Kraemer Platte in a sandwich of 2 wooden frames (to 
make
sure that there is a distance of 20mm to the combs and to the newspaper
isolation and so ensuring acid vapor circulation in the hive, altogether a 
50mm
sandwich).  On the top of the comb-frames of the top brood chamber set up 
an
empty super, isolate the brood chamber, with the Kraemer Platte, from the 
rest
of the empty super with several layers of old newspapers on top (do not use 
plastic, this will keep too much moisture in the hive).  Close the empty 
top
super with the lid.  ATTENTION, do not block the holes in the foil-bag with 
the
frames or the newspapers,  otherwise the vaporization of formic-acid is not
sufficient. 

Leave the Kraemer Platte in place undisturbed for 21days.  After 3 weeks 
take
the plate out and check the weight.  165g of formic-acid should have 
evaporated
during the 21 days for effective Varroa-control.

This method of Varroa-control is ideal for a fall-treatment, starting mid
September after winterfeeding; noon time temperature range must be between 
a
minimum 6 degrees C and maximum 26 degrees C.

Summer/Fall Application
An alternative or additional treatment (in case of strong Varroa 
populations)
is to use the Kraemer Platte after honey harvesting in
summer (early August, some open honey (or sugar) in the combs is important) 
for 7
days, and for an additional 14 days end of September. For this treatment a 
fresh
filled Kraemer Platte is perforated face to face with 3-5 holes/side, 
depending
on the volume of the hive

60-78 liters -> 3 holes / side
79-100 liters-> 4 holes / side
101-120 liters-> 5 holes / side

Only the volume of the brood chamber and honey supers matters, any bottom 
space
must be ignored.

Place the perforated plate vertically in a empty comb-frame (use small pins
to fix the plate) in the center of the empty honey super.
!The bees need unsealed food in the hive! Give sugar syrup before the
application of formic-acid if it is necessary.
The treatment can be done with noon-temperatures of maximum 26 degrees C.
After 7 days take the plate out of the hive, store it in a foil-bag 
(several
plates in one bag are good), and store them horizontal and cool up to 
September,
best would be to weld the storage bag  (ventilation may be useful to 
prevent bad
formic-acid odor). Feed the bees for the winter, and at end of September 
place
the used plates for 14 more days in their hive, like described above for 
the
September-application.  Add additional holes in the plate (2 more than in 
the
table for the regular Fall-application).

This alternative treatment is useful if there is a strong Varroa population 
in
the hives during summer.  For normal Varroa populations the 21 days in 
September
are sufficient.

Just to point it out, in the regular fall treatment the plate is placed 
horizontally on top of the upper brood room, while during the summer 
treatment the plate is placed in a frame vertically in the upper brood room 
(remove temporarily a frame with honey to get space).

I have used these methods of Varroa control for the last 4 years with good
success. Years with extreme cold or hot September/October may cause 
problems,
but however it works!

Ulli Höger
Germany

E-Mail: [email-masked]