Formic acid can be purchased as an 85% concentrate. To reduce the product down to the recommended 65%, 3 parts of the concentrate should be mixed with 1 part water.
A. Precautions
Read the formic acid label before using and take all recommended precautions. Formic acid is strongly corrosive.
Avoid:
• Skin contact – Formic acid can cause skin burns.
• Eye contact – Formic acid can cause blindness.
• Ingestion – Formic acid can cause burns to the stomach and oesophagus and damage to the kidneys.
• Breathing it in – Formic acid can cause potential harmful effects.
Read the formic acid label before using and take all recommended precautions.
B. Operator safety
• Acid-resistant gloves must be worn.
• Goggles should be used.
• Acid-resistant apron, sleeves and boots should also be used, especially when large quantities of formic acid are being handled.
• An air-purifying cartridge-type respirator equipped for organic vapours is recommended when using formic acid, especially in situations where there isn’t good ventilation.
• Have ample water and rags available in case of an accident or spill.
• Avoid using warm formic acid in hot weather. Less of the harmful vapours will be given off when the acid is cold. It may be necessary to cool the formic acid.
• Be careful when disposing of containers. Wash thoroughly with water.
C. Avoiding residues
• Do not apply formic acid when honey supers are on hives, or during nectar flows, if honey is to be extracted for human use.
Do not apply formic acid directly on bees or brood.
Do not apply formic acid when honey supers are on hives.
D. Application methods
Formic acid works by producing a vapour that penetrates the hive. It is important that there is enough space between the top bars of the top super and the lid to allow the formic acid vapour to reach all parts of the colony. Manufacturers of the Canadian product Mite Away recommend placing the bags on thin wooden strips to elevate them slightly above the top bars. It is also important that the formic acid is not applied directly to the bees or brood, since it will kill them.
APPENDIX 2
A variety of application methods have been found to be effective. The methods use formic acid in a manner that extends the time the fumes are in the hive, although some methods require repeat applications at 1-3 day intervals. The four most common application methods are:
• Absorbent pads.
• Application directly to bottom boards.
• Mite wipes.
• Plastic pouches.
Table 1 at the end of this appendix provides a summary of the four methods.
1) Absorbent pads (figure 1)
• The absorbent pads can be made up of any material that will absorb formic acid (e.g., three cloth serviettes, several paper towels, a potholder or disposable nappies).
• The material must be able to absorb 30 ml of 65% formic acid without letting any drip through.
• Prospective material can be tested for absorbency by using water.
• Smoke bees off an area of the top bars of the top brood box of a colony where the pad is going to be placed.
• Lay the absorbent pad on the top bars and dispense 30 ml of 65% acid onto the pad.
CONTROL OF VARROA: APPENDIX 2. HOW TO USE FORMIC ACID
The material must be able to absorb 30 ml of formic acid without letting any drip through.
The treatment needs to be reapplied at 1-4 day intervals, for a total of five or six applications.
Figure 1 Applying formic acid using an absorbent pad.
• If temperatures are above 25oC, or if the cluster is close to the bottom board, pads may be placed on the bottom board instead of the top bars.
• In warm temperatures, formic acid evaporates from pads in less than 24 hours.
• The treatment needs to be reapplied at 1-4 day intervals (depending on evaporation rate), for a total of five or six applications.
APPENDIX 2
2) Application directly on bottom boards (figure 2)
Formic acid can be applied directly on bottom boards:
• To avoid killing bees, smoke the entrance to ensure the cluster is above the bottom board.
• Using a measuring syringe or a drench gun, squirt 15 ml of 65%
acid along each side rail towards the back of the bottom board.
• The treatment needs to be reapplied at 1-4 day intervals (depending on evaporation rate), for a total of five or six
applications.
3) Mite wipes
These are a type of absorbent pad similar to padding found in the bottom of styrofoam meat trays. Mite wipes prolong the evaporation period of formic acid up to 3 days.
• Work in a well-ventilated area, preferably outdoors.
• Prepare only enough pads to use in one day.
• Place the pads to be soaked in formic acid in a plastic storage container that has an airtight cover.
• Pour 40 ml of 65% formic acid per pad onto the pads in the container. As an example, if the container contains 10 pads, pour on 400 ml. Let the pads soak up the acid. Place the cover on the container.
• Use as soon as possible. Storage of pads in acid for more than 2 days can damage the pads.
• Use the pads on hives only when the outside temperature is between 10 and 30oC.
• Before going to an apiary, remove soaked pads from the soaking container. Use gloves or tongs. Place soaked pads in a plastic pail with a lid.
• Smoke the bees off the top bars and place a pad on the top bars of the hive.
• Position the pad close to the edge of the bee cluster at the opposite end to the hive entrance.
• Reapply five times at 4-10 day intervals (depending on evaporation rate).
• Take out used pads from hives before new ones are applied, or after 5-10 days use.
• Do not re-use the pads.
CONTROL OF VARROA: APPENDIX 2. HOW TO USE FORMIC ACID
Figure 2 Applying formic acid directly to a bottom board.
APPENDIX 2
4) Plastic pouches (figure 3)
These consist of zip-lock freezer or vegetable bags filled with absorbent material. Pouches are a convenient treatment method for beekeepers with outlying apiaries because only two trips are necessary for a full treatment. The pouch method extends formic acid release over a 3-4 week period.
• Put 20-30 layers of newspaper in each 27 cm x 28 cm zip-lock bag. There
needs to be sufficient newspaper to absorb all of the formic acid. This can be tested first by using water.
• Add 250 ml of 65% formic acid per bag.
• Seal the bags, excluding most of the air, and stack them flat in a plastic box with an airtight lid. It is a good idea to place the plastic box in another plastic bag to ensure it is airtight.
• Place the plastic box in a freezer for 1 or 2 days before application to any hives.
• Take the box of pouches to the apiary. Remove a pouch and cut openings (windows) in the plastic on one side of the bag exposing the absorbent material with formic acid (figure 3). Each window should measure 1cm x 24 cm.
- For a colony in two supers, cut out two windows at either side of the pouch.
After 10 days cut out a middle window as well.
- For a colony in one super, cut out a window in the middle of the pouch. After 10 days remove one of the side windows.
- For 4 frame nucleus colonies, use smaller zip-lock bags with half of the amount of formic acid used for bigger hives.
• Place one pouch on the top bars or bottom board of a hive with the window facing the bees.
• If used on the top bars, use a wooden rim or inner cover to provide enough room for the bag without crushing and to provide evaporation space for the formic acid.
• If used on the top bars, the window openings should be oriented at right angles to the top bars.
• In cool weather, if the clusters are mainly in the top brood box away from the bottom board, place the bags on the top bars.
• If the bees are close to the bottom board and the temperature is reasonably warm, the pouches can be placed on the bottom board.
As an alternative to zip-lock freezer bags, zip-lock perforated vegetable bags can be used.
To charge them with formic acid, put 250 ml of acid for every bag to be filled in a large plastic airtight container and immerse the absorbent-filled bags in the liquid. Turn the bags several times so that they all absorb an equal amount of acid.
CONTROL OF VARROA: APPENDIX 2. HOW TO USE FORMIC ACID
Figure 3 Cutting a window in a formic acid plastic pouch.
APPENDIX 2
E. When to use formic acid
• Use formic acid only when outside temperatures are between 10o and 30oC.
• Spring treatment – September and October.
• Late summer treatment – February and March.
Table 1 Summary of formic acid application methods
Method Amount used (65%) Treatments Days apart
Absorbent pads 30 ml 5-6 1-4 (based on evaporation rate)
Bottom boards 15 ml 5-6 1-4 (based on evaporation rate)
Mite wipes 40 ml 5 4-10 (based on evaporation rate)
Plastic pouches 250 ml 1 3-4 weeks duration
APPENDIX 2
CONTROL OF VARROA: APPENDIX 2. HOW TO USE FORMIC ACID