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When an AFB hive is found, there is a set of procedures that should be followed to ensure the infected materials associated with that hive do not become a source of infection for other hives.
When AFB is found, a sensible approach to cleaning beekeeping equipment would be as follows:
Scratching an "X" on the surface of a box is not recommended, since the marking may not be obvious, either at night when the hive is to be closed, or when the box is handled by staff members. Most beekeepers can tell stories about AFB hives that were found but not marked adequately, and as a result the whole apiary had to be inspected again when it came time to destroy the infected hive.
It is also very easy to misplace empty boxes, lids and floors stored in the shed for later sterilisation unless they are marked very clearly. The best approach is to mark each piece of hive woodenware that is likely to be salvaged with the word "AFB" written in large letters. The mark should be big enough to be obvious, and bold enough so that it will last until the equipment is sterilised. It is a good idea to mark two adjacent sides of all boxes, so that the mark can be more readily identified if the boxes are placed in a stack.
The AFB information recorded in the site book should be used to produce a written report which is sent to the Management Agency, either in a letter, or in a form provided by the agency for the purpose. The report must include the date the case was found, the apiary location, the number of hives, the Beekeeper Registration Number, and beekeeper name, address and phone number.
Site book records of AFB cases are also necessary to complete the Annual Disease Return. This return must be completed by all beekeepers on or before June 1 each year, and must list the date and location of every AFB case found during the previous 12 months in beehives owned by the beekeeper.
AFB records are also an important management tool for beekeepers. The records provide information on known problem areas and apiaries. They also provide a yardstick against which to judge the success or failure of changes in management practices that have been made in an effort to reduce the incidence of AFB.
It is also important to seal all the cracks in the hive, since bees will use these cracks to fly out during the killing process. Cracks can be filled by covering with masking tape or by pushing small pieces of newspaper into the cracks with the end of the hive tool.
Hives infected with AFB are usually closed and destroyed either in the evening, or during rainy weather, when the bees are not flying. This is done to avoid field bees from the AFB hive flying into neighbouring colonies and possibly spreading the disease.
Because hives infected with AFB are usually found during the daytime, and closed up to be destroyed at night, a second visit to the apiary site is generally required. This can create extra costs for the beekeeper, especially when the apiary is a long distance from home.
Although it is preferable for all bees to be inside the AFB infected colony before the entrance is closed and the colony is destroyed, researchers at Ruakura have found that it is possible to kill colonies while the bees are still flying with little risk of spreading the infection.
A trial was conducted pairing colonies with low level infections (ie., less than 50 larvae/pupae exhibiting AFB symptoms) with colonies not showing any symptoms. At the start of the trial, the pairs of colonies were set up so that their entrances were touching and facing the same way. At the start of the trial, the researchers made sure that one of the colonies had AFB, while the other colony in the pair was uninfected. Then the AFB colony was closed and removed on a sunny day between 1 and 3 p.m., so that foraging field bees from that colony were left behind. The researchers found that most of these field bees flew into the second (no AFB symptoms) colony in the pair.
The trial was repeated with 25 pairs of colonies. Interestingly, none of the colonies remaining behind developed visual symptoms of AFB.32
The petrol should be poured over the top bars as quickly as possible, with care taken to put the lid back firmly on the hive so that bees do not escape. The hive should then be left undisturbed for 10-15 minutes while the petrol vapour kills the bees.
It is important to remember that the petrol is put into the hive to kill the bees, not as a fire accelerant. Petrol should not be used to douse the hive prior to burning. There is sufficient wax in the combs to fuel the fire.
Care should be taken to choose an appropriate site for the hole. The site should be far enough away from healthy hives and fences or buildings to avoid accidents, since beehives burn very vigorously and flames can reach 2-3 times the height of the stack. Windy conditions should also be avoided, and especially swirling winds around sheltered apiaries. It is also very important to clear the surrounding area of any combustible material, since the fire, once under way, will become very intense.
The hole should be about 1 m in diameter (or larger if there are several hives to be burned), and at least 300 mm deep (spade depth). The bottom should slope to provide a sump for unburned, infected honey so that it doesn't choke the fire.
The diseased hive should then be carried to a position nearby the hole (about 3 m), but far enough away so that the hive does not ignite once the fire gets under way. Care should be taken to avoid dropping dead bees or honey on the ground. If practical, the complete hive should be carried into position. Otherwise, individual boxes can be brought to the site one by one in the upturned lid.
It is also very important to take safety precautions just in case the fire begins to get out of hand. A fire extinguisher is recommended, and a shovel and water should always be within easy reach. A fire permit should also be obtained, if this is required by local authorities.
To start the fire, it is best to use rolled up newspaper and a few dried twigs to create a small blaze. Once this is under way, two frames should be chosen that are relatively free of honey. These are propped up against each other in an A-frame over the blaze. The fire will begin to melt and then ignite the beeswax in the frames, and the flames and heat will intensify. The fire can then be fed several frames at a time, taking care to ensure that the fire does not become too intense.
It is important not to put whole boxes of frames onto the fire. If the frames are still soaked with petrol, an explosion can occur, with the potential to cause both injury and accidental fires. Petrol should never be used to accelerate the fire.
If, for whatever reason, petrol-soaked material must be ignited, a petrol trail should be made leading about 2 m from the hole containing the material. A screwed-up piece of newspaper should then be lit and placed at the end of the petrol trail. Petrol-soaked material in a hole should never be lit directly, since if the operator is leaning over the material, the petrol vapour trapped in the hole will create an explosion which could lead to serious injury.
Frames with honey should not be put onto the fire all at once, and should be put around the edge of the fire rather than on top of it. Full frames of honey can sometimes douse the flames. As well, the honey may not completely burn unless there is sufficient other material to fuel the fire.
Lids and floorboards can be angled into the pile on the edge of the hole. A wind tunnel should be left to assist burning.
It is very important to supervise the fire as long as it continues to burn. This may take 2-3 hours for a 1-2 box hive and 4-5 hours for a 3-4 box hive. When the fire has burned down to embers, the remains should be fully covered with all the soil removed from the hole and the grass sod replaced (if appropriate).
Non-plastic hive parts can be sterilised by dipping them in paraffin wax at 160oC for at least 10 minutes. Both the time and temperature are crucial, so it is essential that a timer and thermometer are used.33 Temperatures less than 160oC or dipping times less than 10 minutes will not kill all the AFB spores. The thermometer must be strongly made (eg., commercial food manufacturing grade), and should be capable of reading temperatures up to 200oC.
There are a number of designs for wax dippers. Plans for a basic model are provided in Figure 11. The device is made of welded 5mm plate steel, and has a fire box which can be fuelled with waste wood. There is also a long chimney to provide good draft. The dipper has a capacity of two full depth supers turned on end.
Figure 11. Plans for a paraffin wax dipper AFB sterilisation plant.
Paraffin wax in commercial quantities is available from oil companies. The recommended grade for wax dippers has a melting point of approximately 60oC. A wax dipper capable of holding two supers will require about 90kg of wax. To avoid boil overs, the wax level in the dipper, when melted, should be no higher than 125mm below the rim. The fire will need to burn for 1.5 to 2 hours to bring the dipper up to the required temperature of 160oC.
Care must be taken when handling paraffin wax at high temperatures. There is the obvious risk of burns, so protective clothing needs to be worn. Heavy-duty industrial rubber gloves are recommended, and eye protection should be used. A set of long-handled tongs is an essential piece of equipment to remove the dipped woodenware from the hot paraffin.
Paraffin wax has a flash point of 199o so the temperature must be kept well below this level, especially since the use of an open fire often results in wide fluctuations in temperature. Water sprinkled directly into the fire box can be used to quickly reduce the temperature.
Woodenware to be dipped should be as dry as possible, since excess water can cause the wax to boil over the side of the dipper and ignite when it comes into contact with the fire box.
Water should never be used directly on a paraffin fire, since it will cause an explosion. A cover should be made out of plywood or galvanised metal that fits securely over the top of the dipper. This should be kept close at hand and used to suffocate any paraffin fire that might develop. Dampened sacking can also be used for this purpose, provided that the sacking is not dripping wet.
Sodium hypochlorite is potentially useful to treat beekeeping equipment such as plastic or metal feeders and plastic frames. It is important to note, however, that sodium hypochlorite will only kill what it comes into contact with, so any material to be sterilised must be very clean before treatment.
Care also needs to be taken with the types of materials being treated. Some plastics, metals, and especially leather, can degrade when put into sodium hypochlorite solutions. It is therefore worthwhile carrying out a small trial run before doing any major sterilisation of equipment. The material is not recommended as a disinfectant for gloves, hive tools or smokers, since the 20 minute contact time is crucial to successful destruction of AFB spores.
Sodium hypochlorite solutions must be kept in the dark, since the chemical breaks down in sunlight. The solution should also not be kept for long periods and must be disposed of safely after use.
Finally, a note of caution. The effects of bleach on clothing are well-known, so protective clothing should be worn when using the material. Eye protection is recommended. Some individuals also react adversely (dizziness, fainting) to the fumes of sodium hypochlorite, so extreme care is needed when using the material.
The hives must be stored inside a building. The building should ideally be bee-proof (honey house hot rooms, when not in use, are ideal). However, if sealing all the gaps in the building is not possible (eg., buildings made of corrugated iron), the hives themselves should be kept under a secure tarpaulin or black plastic sheet, with the sides of the cover secured tightly along the floor.
The entrance of every hive should be blocked with pieces of fibreglass batts, since mice will not readily chew this material out. Gaps between the supers should be sealed with newspaper or tape.
It is also important to keep careful track of empty boxes, lids, floor boards, feeders, etc., from AFB infected hives destined for sterilisation, once the contents of the hives have been destroyed. It is a common practice to keep these materials stored until there is time in the beekeeping management schedule to carry out wax dipping or hypochlorite sterilisation.
The best way to identify these materials is to mark them with "AFB", using a felt-tip marker or black crayon. This may seem like an extreme suggestion. However, unless the supers are properly marked, there is a chance that they will be incorporated into stacks of clean supers, especially when staff are unaware of the history of supers kept in a shed. Cases exist where inadequately marked supers or feeders have not been sterilised, and have been put onto healthy hives, resulting in new AFB infections.
It is usually impossible to give feral colonies a visual inspection for AFB symptoms. However, ferals can be sampled for the presence of AFB using the culture test. To take a sample of adult bees for testing, simply hold the opening of a plastic bag over the entrance of the colony when the bees are flying freely. Collect at least 30 bees in the bag, then tie it off. Send the bag to the laboratory together with your name, address, phone number and details regarding the sample (type, location).
If the lab returns a positive test with large numbers of AFB bacterial colonies, the feral colony is likely to have AFB symptoms and should be destroyed.
The easiest way to destroy the colony is to kill it using a powdered insecticide such as Carbaryl wettable powder. Use the powder straight from the container (do not dilute). Sprinkle two tablespoons of the powder in the entrance of the colony. The powder will be picked up on the body hairs of bees, and with be distributed throughout the colony. The colony should die completely within 24 hours.
If the entrance to the colony is so small that the powder cannot be sprinkled directly into entrance, put a similar amount of powder in one end of a short length of hose. Hold the powdered end of the hose up against the entrance and blow through the other end to distribute the powder inside the colony.
Once the hive is dead, the entrance should be blocked with a permanent material (eg., mortar or grafting paste) so that foraging bees from other hives will not be able to enter and rob the colony's honey (and pick up AFB spores).
Many beekeepers kill feral colonies and block their entrances even if the colonies do not have AFB, since it is believed that the colonies may become a disease risk in the future.
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