|
|
|
|
|
One basic understanding underlies all successful beekeeping management techniques designed to reduce and eliminate AFB. The understanding is simple and straightforward, but nevertheless tends to be either down-played or dismissed by some beekeepers. The understanding is as follows:
|
Most AFB infections in honey bee colonies are due to the beekeeping practices that are carried out on those colonies.
|
If the incidence of AFB in a beekeeper's hives is remaining stable, then the beekeeper is probably infecting clean colonies at the same rate that diseased colonies are being found and destroyed. And if the incidence is increasing, then the beekeeper is infecting more colonies than are being found and destroyed.
To alter the situation, the beekeeper can take either one or both of the following approaches:
|
The most effective way to combat American foulbrood disease in any beekeeping outfit is to a) conduct a complete brood inspection before anything is removed from a hive, and b) reduce the exchange of equipment between colonies as much as possible.
|
At a minimum, hives should be inspected at least once in the spring and once in the autumn, but good beekeeping practice also involves further periodic disease inspections throughout the spring build-up period. The first spring inspection should occur once the colony has begun to expand its brood nest. The last autumn inspection can take place even after most of the brood has disappeared from the hive.
Late autumn (April-May) inspections are very quick, but can also be very effective, since a high proportion of the remaining brood that has not emerged out is likely to have some abnormality. Data from seven years of targeted inspections by government inspectors in the 1990's in New Zealand show that the percentage of AFB hives found in the autumn is greater than in the spring.
Failure to give beehives an adequate level of inspection is one of the surest ways to spread AFB within an apiary, and to other apiaries. If an infection is not caught at an early stage, the hive can become weakened in population to the point where it begins to be robbed by foraging bees from other hives. Robbing thus becomes the means of spreading the disease, but only because of inadequate levels of management on the part of the beekeeper.
On the other hand, if the hives are visited on a monthly basis throughout the main production period of the year (August through to April), and the visit includes brood nest inspections, there is very little chance that an AFB infection in a hive can develop to the point where it becomes a source of infective material to bees from other hives.
Inspections should always be targeted to times when these management practices take place. If hives in an outfit or apiary have an AFB problem, a complete brood check should be done before anything is removed from any hive.
Nevertheless, beekeepers are often reluctant to carry out full brood inspections of hives during honey harvesting, particularly when the honey flow has finished and there is a strong potential for robbing. Even the quickest, most efficient inspection will still expose the colony to robber bees, and may result in at least some hives in the yard losing population and condition as a result of robbing attacks.
One solution to the problem is to mark both the hives and the boxes at the time the honey is removed. Use a letter for the apiary and number for the hive (eg., A1). The marking can be done quickly and cheaply with a felt-tip pen.
The number only needs to remain legible for a month or more, until the threat of robbing is past. A full brood inspection can then be carried out on each hive. If AFB is found in a hive, combs and boxes from the infected hive can be removed and dealt with, either when they turn up at the uncapper, or in the stacks of extracted (wet) supers.
If there is only 1 frame showing AFB symptoms in a hive with 12 frames of brood, there is a 75% chance of the infection being missed if only 3 frames of brood are checked (Table 4). Nevertheless, some beekeepers only ever inspect 3 brood frames per hive, and often only in the top super.
|
Brood frames |
3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
|
Frames Inspected |
||||||||||
| 1 | 66 | 75 | 80 | 83 | 86 | 88 | 89 | 90 | 91 | 92 |
| 2 | 33 | 50 | 60 | 67 | 71 | 75 | 77 | 80 | 82 | 83 |
| 3 | 0 | 25 | 40 | 50 | 57 | 63 | 66 | 70 | 73 | 75 |
| 4 | 0 | 20 | 33 | 43 | 50 | 55 | 60 | 64 | 67 | |
| 5 | 0 | 17 | 28 | 38 | 44 | 50 | 55 | 58 | ||
| 6 | 0 | 15 | 25 | 33 | 40 | 46 | 50 | |||
| 7 | 0 | 13 | 22 | 30 | 36 | 41 | ||||
| 8 | 0 | 11 | 20 | 27 | 33 | |||||
| 9 | 0 | 10 | 18 | 25 | ||||||
| 10 | 0 | 9 | 17 | |||||||
| 11 | 0 | 8 | ||||||||
| 12 | 0 |
Table 4. Percentage chance of not identifying an AFB hive with diseased larvae on only 1 brood frame when different numbers of frames are inspected.
It takes about 4 times longer to disassemble a two box hive and inspect all of the brood frames than to inspect 3 brood frames in the top box. However, this increase in labour is negligible compared to the time and expense required to simply get to the apiary. Since considerable effort is taken to visit each apiary site, it makes sense to do a thorough and effective job once there.
There are good examples of beekeepers in New Zealand with above average levels of AFB in their hives significantly decreasing the incidence by simply increasing the number of brood frames inspected in every hive.
The chances of finding light infections of AFB (less than 50 infected cells per hive) are greatly reduced when there are so many bees on the brood frame that a majority of the cells are obscured.
As with most jobs, showing someone once how to recognise AFB symptoms is not enough. Differential diagnosis of AFB is a complex task, and even professional inspectors who routinely deal with AFB outbreaks are often confused by symptoms that do not fit the classic descriptions given in books.
Beekeepers employing staff should periodically audit the performance of staff members in AFB inspection and recognition. The most important time to check these skills is at the beginning of the beekeeping year, since AFB will not have been a priority for staff during the winter period.
Because abnormal brood is often present in beehives, a sure sign of inattention to AFB recognition is when an employee seldom (if ever) asks for a second opinion on disease symptoms from fellow workers. Employees should be encouraged to seek these second opinions whenever they are working beehives and examining brood.
These include:
The extent of change in management practices will depend on the level of AFB currently in the beekeeping outfit. The changes mostly involve reducing the number of beehive components being swapped between hives.
There are three main types of quarantine that can be usefully applied to honey bees. These are hive, apiary and area quarantine. They all serve to limit the impact of hive management on the spread of AFB.
A hive quarantine is where each honey bee colony is managed by itself, with no interchange of equipment between hives. It is usually only employed where there is a significant risk of equipment that might be swapped between colonies being contaminated with AFB spores (ie., where the outfit has a very high incidence of AFB).
As an example, consider a beekeeper who has a 20% AFB incidence. The beekeeper decides to impose a hive quarantine. To do so, the beekeeper must isolate and keep together all beehive equipment associated with each honey bee colony.
The beekeeper starts by assigning a unique number to each hive. The number is recorded in a permanent fashion on a piece of equipment that is likely to always stay with that colony. A good choice is to put the number on the floor board, since it is rarely swapped between colonies.
To permanently record the unique number, the beekeeper nails a small animal ear tag on the front of each bottom board where it can be easily seen. From then on, no equipment is swapped between colonies. Queen excluders, feeders, division boards, etc., either stay with the colony, or if they are taken away for storage, they are marked with the unique number using a felt-tip pen. When the pieces of equipment are needed again, they are only put on the hive with the unique number.
Honey supers are also numbered when removed. The frames are extracted together and are put back into the same super. If keeping track of the frames during extraction is a problem (because a large capacity extractor is being used), several cans of spray paint are kept at hand in the extraction shed. Before extraction, a coloured line is drawn across the top bars of the frames in the box, and the box is also marked with a dot of the same colour paint. No boxes containing frames with the same colour are put into an extractor batch, and no frames of another colour are put back into the box.
If AFB is found in any hive, the stored equipment marked with that hive's unique number is located. Frames are destroyed, and all other equipment is sterilised.
This total destruction policy may seem quite harsh. However, faced with a bad AFB outbreak in the spring, many beekeepers have wished that they could identify the honey supers that came off those infected hives the previous autumn.
Hive quarantine is obviously very time consuming, and requires the beekeeper to be highly organised. It lends itself more to hobbyist beekeepers, and beekeepers with smaller hive holdings. The time taken to implement a hive quarantine can be less than first imagined, however, and hive quarantine has also been used by commercial beekeeping operations, often with dramatic effects.
When the hive quarantine is in place, and the honey supers are on the hives, a starting point exists where no further AFB hives are going to be created. The work then involves inspecting all hives at regular intervals and destroying all equipment associated with any hive found to be infected. Hives must also be well-managed and fed so that as few hives as possible either starve or become queenless. It is far more difficult to determine the disease status of hives that die out.
If all the available equipment is used on the hives each year, if comprehensive inspections are carried out, and if there are few outside sources of infection such as neighbouring apiaries or feral colonies, it should be possible using hive quarantine to eliminate AFB from almost any sized outfit within a couple of years.
Hive quarantine can also be used for colonies that return a positive culture test, but have no clinical disease symptoms. In this case, the hive and its equipment should be isolated and treated separately until it returns a negative test. If there are a number of hives testing positive, they can all be moved to the same apiary to reduce the possibility of these hives cross-infecting other colonies in the outfit.
An apiary quarantine is where each apiary is managed separately, with no interchange of equipment between apiaries. This type of quarantine is used by many beekeepers in New Zealand, regardless of the AFB incidence in their hives.
To create an apiary quarantine, the beekeeper marks all the beehive equipment in the apiary using a single code letter or number. Once the equipment has been marked, it remains with that apiary, in much the same fashion as with the hive quarantine.
An apiary quarantine has the advantage that it is much less time-consuming than a hive quarantine. Apiary quarantine is used as a matter of routine in some beekeeping outfits. If an AFB problem develops, it will probably only affect the colonies in one yard, rather than the whole outfit.
Beekeepers use a number of modifications of the apiary quarantine system. Many beekeepers do not use routine apiary quarantine, and only quarantine any apiary where an AFB hive is found. They keep the quarantine in place until the apiary has been free of AFB for a specified time (usually 18 months to 2 years).
Other beekeepers quarantine the honey supers coming off an apiary at extraction time, and extract and store them as individual apiary lots. The quarantine is kept on the supers until all of the spring management (including several full brood inspections) is completed. If no AFB is found in the apiary, the quarantine is lifted, and the supers are used in the outfit wherever they are needed. If AFB is found, the supers are only used on the quarantined apiary. If more supers are needed in that apiary, they are taken from the non-quarantine group and become part of the quarantine.
Beekeepers sometimes add a hive quarantine to their routine apiary quarantine when an AFB outbreak in an apiary occurs. In this case, a second code letter or number is used in addition to the apiary code (eg., "A" for the apiary, and "1" for the hive) to identify each hive in the apiary.
The major drawback with an apiary quarantine is that it does not lend itself to beekeeping outfits where hives are shifted to different locations during the year. This is particularly a problem when hives are used in pollination and the apiaries are split up, with hives from a single apiary being placed in several different orchards.
However, there are some beekeepers engaged in pollination who make effective use of apiary quarantine. They either utilise dump sites after pollination to re-combine the hives back into the original apiary unit, or drop off partial loads in post-pollination apiaries, making sure they get all the hives from the original apiary back together.
Area quarantine is not used as extensively by beekeepers as hive or apiary quarantine, and tends to be limited to outfits with large hive holdings spanning several distinct geographic areas. An area quarantine might consist of dividing a beekeeping outfit into two parts: those apiaries with a recent history of AFB, and those without. The two parts of the outfit are managed separately, with no interchange of equipment between parts. Apiaries are added to the AFB-free part if they remain free of the disease for a certain length of time, or are added to the AFB part if a colony develops the disease.
Selection of breeder queens producing worker bees that show uncapping and removal traits is the most practical means of increasing the level of hygienic behaviour in hives. A beekeeper can concentrate on rearing just queens from these breeders, although the increase in gene frequency would be quicker if both queen and drone selection was used.
The test for hygienic behaviour is simple and straightforward, and does not interfere with the normal queen rearing process. It should therefore be a part of every beekeeping outfit's queen rearing programme.
To carry out the test, select a comb of freshly capped brood in the hive containing the breeder queen. The brood must be in the prepupal stage, just after it has been capped. Take a long, thin pin (such as an insect mounting pin or a small needle) and push it through the capping to kill the prepupa. Be careful not to disrupt the face of the capping any more than is necessary to insert and then remove the pin.
Continue putting the needle through enough adjacent cappings so that a circular pattern is created (about 8 cells). Mark the frame with a pen or thumb tack and put it back in the hive.
Three days later, remove the frame. If the bees have hygienic behaviour, the circular pattern should be obvious, since the bees will have uncapped and removed the killed brood.
Carry out the test several more times to see if the hive produces consistent results. If it does, the queen heading the hive will have passed the hygienic behaviour test and can be considered as a breeder for queen production.
Home NZ Bkpg Bee Diseases Organisation Information Contacts
, webmaster of the site...