AVM-GSL
Over the Counter
Varroxal 1 g/g Bee-hive Powder for Honey Bees
Active ingredient: Oxalic Acid Dihydrate
Form
Powder
Species
Honey bees
Manufacturer
Andermatt BioVet GmbH
VMD MA No.
36234/5000
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Paying less for Oxalic Acid Dihydrate
-
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Clinical information
Varroxal 1 g/g Bee-hive Powder for Honey Bees — SPC Details
Source: VMD Summary of Product Characteristics (SPC). Last updated 27 Mar 2026.
*One evenly filled, flat measuring spoon contains 1 g oxalic acid dihydrate.
Caking of the product may occur, these agglomerations/lumps may be physically
broken down with a spoon. Caking may result in increased dissolution time.
Evaporation/sublimation application:
Place 2 spoonfuls* of the product into a suitable device (e.g. Varrox or Varrox Eddy
vaporizer) for evaporation to treat one colony. Follow the instructions of the
evaporation device. Keep hive entrance closed after the treatment for some time to
prevent bees from exiting the hive.
Trickling application:
• Mix 8 spoonfuls*
of the product with 200 ml of lukewarm sugar syrup 1:1 (30 to 35°C) in a
non-metallic container to obtain a 4% (m/V) oxalic acid dihydrate solution
(which corresponds to a 2.8% (m/V) oxalic acid solution) to treat four
colonies.
• Mix 12 spoonfuls* of the product
with 200 ml of lukewarm sugar syrup 1:1 in a non-metallic container to
obtain a 6% (m/V) oxalic acid dihydrate solution (which corresponds to a
4.2% (m/V) oxalic acid solution) to treat four colonies.
Close the container and shake vigorously until the oxalic acid dihydrate powder is
completely dissolved. Wait until the solution is clear. The trickling solution is now
ready to use and should be applied lukewarm.
Fill a syringe (60 ml) or similar device with the needed amount of ready-to-use
solution to treat a colony. The dose per comb side is 0.25 ml/dm
.
Amounts of ready-to-use trickling
solution per row of brood frames
Small frames (DNM, National, Simplex,
WBC, Zander)3-4 ml
Large frames (Dadant, Swiss Hive)5-6 ml
For two storey hives, trickle first the lower brood chamber and then the upper brood
chamber.
Spraying application:
Mix 6 spoonfuls* of the product with 200 ml of lukewarm tap water
sprayer to obtain a 3% (m/V) oxalic acid dihydrate solution (which corresponds to a
2.1% (m/V) oxalic acid solution) to treat three colonies.
Close the hand sprayer and shake. The solution is now ready to use. Spray 2-4 ml of
the solution over each side of the comb that are covered by bees. If only half of the
frame is covered with bees the dosage must be reduced by 50%. The maximum
dose is 80 ml per hive. The total volume required varies with the hive system:
-
treated with a dose of 0.3 ml/dm
of comb fully covered with bees and for the
most common hives as follows:
Hive systemAmounts of ready-to-use spraying
solution per brood frame side
covered with bees
DNM, National, Simplex, WBC, Zander2 - 3 mlCommercial beehive, Langstroth, Swiss
hive
2.5 - 3.5 mlAZ-hive (SI), Dadant3 - 4 ml
-
ready-to-use spraying solution per kg of bees.
For an accurate dosage spray with your hand sprayer 10 times into a measuring cup
and calculate the volume for one pump action. Calculate how many pump actions
are required to treat one side of a frame. The combs should be sprayed at a 45°
inclination in order to minimize the direct spraying into the cells.
Caking of the product may occur, these agglomerations/lumps may be physically
broken down with a spoon. Caking may result in increased dissolution time.
Evaporation/sublimation application:
Place 2 spoonfuls* of the product into a suitable device (e.g. Varrox or Varrox Eddy
vaporizer) for evaporation to treat one colony. Follow the instructions of the
evaporation device. Keep hive entrance closed after the treatment for some time to
prevent bees from exiting the hive.
Trickling application:
• Mix 8 spoonfuls*
of the product with 200 ml of lukewarm sugar syrup 1:1 (30 to 35°C) in a
non-metallic container to obtain a 4% (m/V) oxalic acid dihydrate solution
(which corresponds to a 2.8% (m/V) oxalic acid solution) to treat four
colonies.
• Mix 12 spoonfuls* of the product
with 200 ml of lukewarm sugar syrup 1:1 in a non-metallic container to
obtain a 6% (m/V) oxalic acid dihydrate solution (which corresponds to a
4.2% (m/V) oxalic acid solution) to treat four colonies.
Close the container and shake vigorously until the oxalic acid dihydrate powder is
completely dissolved. Wait until the solution is clear. The trickling solution is now
ready to use and should be applied lukewarm.
Fill a syringe (60 ml) or similar device with the needed amount of ready-to-use
solution to treat a colony. The dose per comb side is 0.25 ml/dm
.
Amounts of ready-to-use trickling
solution per row of brood frames
Small frames (DNM, National, Simplex,
WBC, Zander)3-4 ml
Large frames (Dadant, Swiss Hive)5-6 ml
For two storey hives, trickle first the lower brood chamber and then the upper brood
chamber.
Spraying application:
Mix 6 spoonfuls* of the product with 200 ml of lukewarm tap water
sprayer to obtain a 3% (m/V) oxalic acid dihydrate solution (which corresponds to a
2.1% (m/V) oxalic acid solution) to treat three colonies.
Close the hand sprayer and shake. The solution is now ready to use. Spray 2-4 ml of
the solution over each side of the comb that are covered by bees. If only half of the
frame is covered with bees the dosage must be reduced by 50%. The maximum
dose is 80 ml per hive. The total volume required varies with the hive system:
-
treated with a dose of 0.3 ml/dm
of comb fully covered with bees and for the
most common hives as follows:
Hive systemAmounts of ready-to-use spraying
solution per brood frame side
covered with bees
DNM, National, Simplex, WBC, Zander2 - 3 mlCommercial beehive, Langstroth, Swiss
hive
2.5 - 3.5 mlAZ-hive (SI), Dadant3 - 4 ml
-
ready-to-use spraying solution per kg of bees.
For an accurate dosage spray with your hand sprayer 10 times into a measuring cup
and calculate the volume for one pump action. Calculate how many pump actions
are required to treat one side of a frame. The combs should be sprayed at a 45°
inclination in order to minimize the direct spraying into the cells.
None.
Target species: Honey bee
Very common (>1 colony / 10 colonies
treated):
Increased bee mortality rate
Common (1 to 10 colonies / 100 colonies
treated):
Agitation of colony
Undetermined frequency
(cannot be estimated from the available
data):
Hive weakness
1
with the trickling or spraying treatment.
during treatment.
in spring with the trickling treatment.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian,
to either the marketing authorisation holder or the national competent authority via
the national reporting system. See the package leaflet for respective contact details.
Very common (>1 colony / 10 colonies
treated):
Increased bee mortality rate
Common (1 to 10 colonies / 100 colonies
treated):
Agitation of colony
Undetermined frequency
(cannot be estimated from the available
data):
Hive weakness
1
with the trickling or spraying treatment.
during treatment.
in spring with the trickling treatment.
Reporting adverse events is important. It allows continuous safety monitoring of a
veterinary medicinal product. Reports should be sent, preferably via a veterinarian,
to either the marketing authorisation holder or the national competent authority via
the national reporting system. See the package leaflet for respective contact details.
Use only in brood-free colonies due to a lack of efficacy on Varroa inside brood cells.
Treatments should be carried out at times of the day when bees are not flying. The
summer treatments of swarms, artificial swarms or man-made broodless colonies
must be followed by an autumn/winter or spring treatment against Varroa.
The efficacy may vary between colonies due to the conditions of use (temperature,
reinfestations etc.). Use the product as part of an Integrated Pest Management
program with regular mite monitoring. Using different substances during the year
reduces the risk of building resistance.
The application of high amounts of oxalic acid could lead to higher bee mortality;
therefore, exact dosing is necessary.
Evaporation/sublimation application: To be used in the broodless colony as a single
treatment in autumn/winter at outdoor temperatures between 2°C and 10°C. A
second evaporation treatment after a 2-week interval is only recommended for:
- Heavily reinfested colonies with a remaining infestation of over 6%.
- Colonies where patches of sealed brood cells are present during wintertime.
Trickling application: To be used in the broodless colony in summer after the honey
harvest or in autumn/winter as a single treatment at outdoor temperatures above -
15°C.
Spraying application: To be used in swarms, artificial swarms or man-made
broodless colonies as a single treatment in spring/summer or in autumn/winter at
outdoor temperatures above 8°C. A second spraying treatment after a 2-week
interval is only recommended for heavily reinfested colonies with a remaining
infestation of over 6%.
Special precautions for safe use in the target species:
Avoid disturbance to the hives for several days after treatment.
If bees are treated more than once per generation of worker bees, it can result in
damage to the bees and a reduction in strength of the colony.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
This product is highly acidic and corrosive and could cause severe irritation of eyes,
oral and respiratory mucosa, irritation of the skin, and contact dermatitis. Inhalation
may cause nosebleeds, headaches, and/or vomiting. Avoid inhalation, accidental
ingestion and skin and eye contact including hand-to-mouth and hand-to-eye
contact. Children should not come in contact with this product. Keep children away
when preparing and administering this product. Beware of bystanders. Avoid all
direct contact with the product during preparation, use, cleaning, and disposal.
Personal protective equipment consisting of chemical resistant gloves, an FFP3
mask, and safety glasses should be worn when handling and applying the product.
During preparation, handle the product outdoors or in well-ventilated areas. When
spraying and evaporating, apply product with your back to the wind. Remove
contaminated clothing immediately and wash before re-use. Do not eat, drink or
smoke during handling of the product. Used measuring devices and empty
containers should be thoroughly washed and/or disposed of immediately and not left
in the sight and reach of children.
In case of accidental ingestion, rinse mouth with water and drink plenty of water or
milk. Do not induce vomiting. In case of accidental inhalation, move to fresh air and
rest in a position comfortable for breathing. In case of skin or eye contact,
immediately rinse thoroughly with water and remove contaminated clothing or
contact lenses. If skin/eye irritation persists, or if the product has been inhaled or
ingested, seek medical advice immediately and show the package leaflet or the label
to the physician. Wash hands after use.
Special precautions for the protection of the environment:
Not applicable.
Other precautions:
Corrosion sensitive materials should be prevented from contact with oxalic acid
dihydrate solutions.
Caking of the product may occur, these agglomerations/lumps may be physically
broken down with a spoon. Caking may result in increased dissolution time.
Treatments should be carried out at times of the day when bees are not flying. The
summer treatments of swarms, artificial swarms or man-made broodless colonies
must be followed by an autumn/winter or spring treatment against Varroa.
The efficacy may vary between colonies due to the conditions of use (temperature,
reinfestations etc.). Use the product as part of an Integrated Pest Management
program with regular mite monitoring. Using different substances during the year
reduces the risk of building resistance.
The application of high amounts of oxalic acid could lead to higher bee mortality;
therefore, exact dosing is necessary.
Evaporation/sublimation application: To be used in the broodless colony as a single
treatment in autumn/winter at outdoor temperatures between 2°C and 10°C. A
second evaporation treatment after a 2-week interval is only recommended for:
- Heavily reinfested colonies with a remaining infestation of over 6%.
- Colonies where patches of sealed brood cells are present during wintertime.
Trickling application: To be used in the broodless colony in summer after the honey
harvest or in autumn/winter as a single treatment at outdoor temperatures above -
15°C.
Spraying application: To be used in swarms, artificial swarms or man-made
broodless colonies as a single treatment in spring/summer or in autumn/winter at
outdoor temperatures above 8°C. A second spraying treatment after a 2-week
interval is only recommended for heavily reinfested colonies with a remaining
infestation of over 6%.
Special precautions for safe use in the target species:
Avoid disturbance to the hives for several days after treatment.
If bees are treated more than once per generation of worker bees, it can result in
damage to the bees and a reduction in strength of the colony.
Special precautions to be taken by the person administering the veterinary medicinal
product to animals
This product is highly acidic and corrosive and could cause severe irritation of eyes,
oral and respiratory mucosa, irritation of the skin, and contact dermatitis. Inhalation
may cause nosebleeds, headaches, and/or vomiting. Avoid inhalation, accidental
ingestion and skin and eye contact including hand-to-mouth and hand-to-eye
contact. Children should not come in contact with this product. Keep children away
when preparing and administering this product. Beware of bystanders. Avoid all
direct contact with the product during preparation, use, cleaning, and disposal.
Personal protective equipment consisting of chemical resistant gloves, an FFP3
mask, and safety glasses should be worn when handling and applying the product.
During preparation, handle the product outdoors or in well-ventilated areas. When
spraying and evaporating, apply product with your back to the wind. Remove
contaminated clothing immediately and wash before re-use. Do not eat, drink or
smoke during handling of the product. Used measuring devices and empty
containers should be thoroughly washed and/or disposed of immediately and not left
in the sight and reach of children.
In case of accidental ingestion, rinse mouth with water and drink plenty of water or
milk. Do not induce vomiting. In case of accidental inhalation, move to fresh air and
rest in a position comfortable for breathing. In case of skin or eye contact,
immediately rinse thoroughly with water and remove contaminated clothing or
contact lenses. If skin/eye irritation persists, or if the product has been inhaled or
ingested, seek medical advice immediately and show the package leaflet or the label
to the physician. Wash hands after use.
Special precautions for the protection of the environment:
Not applicable.
Other precautions:
Corrosion sensitive materials should be prevented from contact with oxalic acid
dihydrate solutions.
Caking of the product may occur, these agglomerations/lumps may be physically
broken down with a spoon. Caking may result in increased dissolution time.
Do not use simultaneously with other acaricides.
Store in the original package. Store in a dry place. Protect from direct sunlight.
Honey: zero days. The product should not be used during honey flow. Administer the
treatment without honey supers mounted.
4.
treatment without honey supers mounted.
4.
This information is sourced from the official Summary of Product Characteristics (SPC) published by the Veterinary Medicines Directorate (VMD). It is provided for informational purposes only and does not replace professional veterinary advice. Always consult your vet before administering any medication.
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