Using Formic & Oxalic Acids
for treatment of Varroa & Tracheal
& Honey bee parasitic mites
Michael Young
Institute of Northern Ireland Beekeepers
Oxalic acid in nature
Occurs naturally in plants
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Carrots contain 500 mg/kg
Broccoli contains 900 mg/kg
Rhubarb leaves
Occurs naturally in insects.
Oxalic acid in honey
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Natural constituent of honey
Values range between 8 and 300 mg/kg in
honey
Moist vegetables contain much more OA
than honey
Low risk of residues in honey.
Bernardini and Gardi 2001
Oxalic acid use in Europe
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Recently registered (2005) and extensively
used in Europe
Maximum residue limits established Dec.
2004 at 50 millequivalents of free acids
If used according to European
recommendations, there is no risk of
problems with honey.
Rademacher and Imdorf 2004
Methods of application
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Oxalic acid is applied by spraying, trickling
or evaporating
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Trickling is the preferred application in Europe
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Effectiveness greater than 90%
Mechanism of acaricidal action has not
been investigated in detail.
Rademacher and Imdorf 2004
Trickle method
Trickling a solution of water-sugaroxalic acid is a promising method to
keep Varroa levels down.
100 parts water and
100 parts sugar by weight
75 g Oxalic-1 liter water- 1 kg sugar
will make 1,66 liter solution that is
enough for 50 hives.
This mixed up solution will keep for a
few weeks only and should be used at
once.
Use 20 to 35 ml solution for each hive
depending on the size of the treated
colony.
Easy Access
On a 2 box hive the solution is
distributed according to the amount of
bees in each box. The top box
normally holds more bees and is
given 70% of the solution
The bottom box is given 30% of
the total solution.
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The solution is distributed evenly in the gap between the
top bars, so it will drip down and reach as many bees as
possible.
(5-6ml between each frame)
Time per hive 1,5 min.
Spray Method
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Not necessary to remove individual frames
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Spray top and bottom cluster
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Quick and effective.
Vaporizers
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Russian
Gas
Battery 12volt
Efficiency from the Oxalic Acid
evaporation in a different dosage
Test result
Without
treatment
water
Oxalic Acid evaporation (g/Beehive
0,5g
1,0g
2,0g
3,0g
5,0g
Lowest effect
0,0%
1,3%
51,7%
93,2%
91,7%
98,1%
99,0%
Average effect
1,2%
4,8%
82,8%
96,0%
97,2%
99,0%
99,2%
Highest effect
2,7%
11,5%
96,0%
99,2%
99,6%
99,7%
99,8%
Beehives per
6
test
8
12
10
13
11
5
European Guidelines
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Make a solution by dissolving 35g OA in 1 liter of
lukewarm solution sugar water (1:1 solution)
Recommended dose is 5-6 ml per occupied
frame space
Treat in Autumn or early winter
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Most effective in broodles colonies
Treat when temperature. Is 32-55°F
Wear glves and safety goggles
The physical properties
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of oxalic acid may be of interest in this
connection. The stuff one buys is usually oxalic acid dihydrate, which is a
crystal which has two water molecules attached to each oxalic acid
molecule.
The CRC Handbook of Chemistry and Physics gives the following properties
for oxalic acid dihydrate:
On heating:
1) The water of hydration leaves at 101.5 degrees C. The water boils off
leaving anhydrous oxalic acid crystals.
2) At 157 degrees C the oxalic acid starts to sublime (goes directly from
solid to gas)
3) At 189 degrees C the oxalic acid which has not yet sublimed
decomposes to
formic acid and carbon monoxide.
Treatment Considerations
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Mix fresh
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Store unused material in refridgerator
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Safety equipment
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Trickle
Acid resistant gloves
Goggles
Spray or fumigation
As above as well as
Acid rated respiratory cartridge
Results
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Spray treatment reduces varroa infestation
by 92% when compared to untreated
(mean)
Trickle treatment reduced varroa
infestation by 87%
Effectiveness of spray and trickle
treatments are not significantly different
No Oxalic Acid resistant
possible.
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It works by destroying the mite's suction
ability, stopping it from feeding from the
bee. Effectively, the mite starves to
death.
Essential advantages over the actual
usually fighting methods are:
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no delays in the honey, beeswax and propolis
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very good bee compatibility
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high degree of effectiveness , up to 99% in
brood free colonies
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no early ageing of the bees (important to
population of the bees in spring)
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outside any time of honey-collection usable
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very user kind for the beekeeper.
Caution:
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Oxalic acid in its crystalline form is poisonous and
should be handled carefully. It should not be allowed
to contact the skin and it is essential that the dust is
not inhaled
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Weigh and mix outdoors, preferably in a light breeze
to take any dust away from you. In the solution given
above it is safe to handle with rubber gloves.
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Oxalic acid is not dangerous if precautions are
taken. Wear rubber gloves and be careful not to let
the acid touch your skin or eyes. Wear old clothes,
use protective mask, and glasses.
Annual Bee meeting York
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Oxalic Acid can only be used by requiring
a prescription from the vet
It can only be used as a hive cleanser
All beekeepers have to keep records of all
medicines used as a treatment for bees
If not! It carries a two year jail sentence
Thank You!
Credits Dr Marion Ellis
Nebraska University