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This section contains a number of case studies of beekeepers who have successfully reduced the incidence of AFB in their hives. The case studies all work on the same premise, ie., that diseased colonies are found and destroyed faster than new colonies are being infected. The methods used depend on the type of beekeeping operation (for example honey production vs. pollination), and the level of AFB incidence in the outfit.
Type - Honey and Pollination
In this case study, the beekeeper was not the person who first identified the AFB problem. High levels of AFB were found during routine inspections of hives carried out as part of the NBA AFB Control Programme. The beekeeper was not able to correctly identify the symptoms of the disease, and asked for help in both inspection and AFB recognition training.
An initial inspection of the outfit by a government apiculture officer revealed a disease incidence of approximately 25%. The officer believed that there was a high probability that the incidence would reach 50% the following year, and potentially 100% in the near future, if major changes in beekeeping management did not take place.
The first action following the complete brood check of all 800 hives was the destruction of 200 colonies, and the sterilisation by paraffin dipping of the supers, floor and lids associated with those colonies.
The next step was to ensure that the spread of the disease was halted. All remaining colonies were given a unique number, with a tag stapled on each floorboard. From that point on there was no further exchange of hive parts between colonies. Any hive part that was removed from a colony was marked with the unique number using a permanent marker pen, and those hive parts were only put back on the numbered colony.
Honey supers were also marked with the unique number. For each super, the top bars of the frames and the side of the box was marked with a distinctive colour of paint. When the honey was extracted, the coloured frames were all put back in the same super.
The supers were returned to the hives bearing the unique number the next spring. Any hive that died over winter that didn't show AFB symptoms still had the wax melted out, frames burnt and remaining equipment sterilised by wax dipping.
To maintain hive numbers at about 800, large numbers of splits were made. Each split was marked in such a way that both the split and parent colony could be identified and checked if either developed AFB.
Although the beekeeper did not always adhere completely to the system, the incidence of AFB in the outlet still declined to 10% in the second year, and to less than 2% during the third year.
This hive quarantine method used in this case study was obviously very time consuming and required good record keeping. However the results speak for themselves. To change from a situation with very high disease levels that were quickly increasing, to less than 2% incidence, all in the course of 2 years, demonstrates what can be done with will, determination and a conscious effort to change management practice and stick to a hive quarantine. The alternative would have been AFB infection in almost all of the hives in the outfit, and the possible spread of the disease to apiaries belonging to a number of other beekeepers.
Type - Pollination side-line
This outfit was built up during the growth phase of the kiwifruit industry. With the downturn in kiwifruit, the owner of the outfit decided to put effort into other ventures, and employed staff on a part-time basis to feed hives, prepare them for pollination, and shift them into orchards. The owner decided not to produce a honey crop, so the hives were not visited during the summer period.
Hive numbers reduced over several years, with part-time staff collecting dead-out hives in the spring and storing them in the shed. AFB was occasionally picked up in live hives, but at levels of about 2% per annum.
Eventually, the owner decided to prepare the remaining hives for sale, and so employed a more experienced beekeeper to make splits, using the dead-out hive equipment in the shed. The experienced beekeeper inspected every brood frame in that equipment for AFB scale, but because of the presence of mould and pollen mites, it was almost impossible to find any symptoms of disease.
A total of 200 splits were made and put into pollination. However, when it came time to offer the hives for sale in the summer, an inspection of several apiaries by a potential buyer found a number of the hives to be diseased.
The experienced beekeeper then inspected all hives three times before winter, finding AFB in 15%. The disease was present in all 20 apiaries, spread over a large geographic area. The remaining hives were inspected 3 more times next spring, with a further 10% of hives found to be infected.
Since the hives were not used for honey production, and the only extra hive equipment was from the dead-outs stored in the shed, it appeared that the source of the infection was most probably comb from those dead-outs. This conclusion was supported by the fact that AFB was spread through all of the apiaries.
A large amount of comb and boxes still remained in the shed. The owner decided to destroy remaining combs, and paraffin dip all boxes, lids and floor boards. Frames and foundation were produced to re-fill all boxes.
The remaining hives were put into pollination, and once again no honey crop was produced. In the middle of the honey flow, splits were made from the strongest colonies, using the boxes with new frames and foundation.
A further 3% of colonies (including the splits) were found to be infected in the autumn. The next spring, AFB was confined to one apiary, but in 30% of the hives. One of the splits appeared to have been robbed out over the winter months. By the next spring, AFB levels had reduced to just over the national average (about 0.5%).
The type of quarantine used in this case study was a modified hive quarantine. No gear was swapped between colonies, and no honey production took place. However, individual hives were not marked.
This case study illustrates two important factors involved in AFB spread. The first is that lack of proper training and supervision of staff in the area of AFB identification can result in serious down-stream consequences for a beekeeping business. The second is that stored boxes of comb should always be treated with suspicion, especially when there is little if any knowledge of the history of the gear.
The case study also shows that making splits can be a useful method of rapidly re-establishing hive numbers after an AFB outbreak, provided that equipment is quarantined to the parent colony and the split. It is essential, however, to give these colonies a greatly increased level of management and inspection to prevent any further outbreaks of disease.
Type - Honey Production
This outfit has been in existence for three generations, with some apiaries in the same locations for over 40 years. AFB was a problem in the early years of the business, with feral colonies being blamed. However, extensive willow clearance along the rivers, and the advent of German wasps, were suggested causes for a reduction in the population of ferals during the past decade.
Ten years ago, a new beekeeper put apiaries within flying distance of a number of the outfit's sites. Within two years, the established beekeeper began finding AFB in a small number of hives (about 1%). The established beekeeper was concerned, however, since no AFB had been present in the outfit for the previous 7 years.
The next spring, the new beekeeper asked the established beekeeper to have a look at one of the new beekeeper's yards. The new beekeeper felt the hives weren't doing very well, but wasn't sure what the problem was. The new beekeeper had not received any previous training in AFB inspection techniques, and did not know how to identify symptoms of the disease.
The established beekeeper identified AFB in 75% of the hives in the apiary. Several infected hives appeared to have been robbed out. The new beekeeper had been transferring combs from stronger colonies to weaker ones trying to help them survive.
A government inspector was called in and found similar levels of infection in the new beekeeper's other 5 yards, almost all within flying distant of the established beekeeper's apiaries.
The new beekeeper decided to destroy all remaining beehives, and gave up beekeeping. The established beekeeper, however, was still left with the problem of what to do.
Since the disease had been in the new beekeeper's hives for several years, and since the established beekeeper did not have any record of the whereabouts of honey supers that had previously been on apiaries close to the new beekeeper's sites, the established beekeeper decided to impose apiary quarantine throughout the outfit.
When the honey crop was removed, honey boxes were put into stacks according to apiary and identified with 100mm x 300mm galvanised metal tags. One tag was used per apiary per stack. All apiaries were given a thorough brood inspection following honey removal, but no AFB was found. All apiaries were given three further inspections of all brood frames during the next spring build-up period. A total of 30 AFBhives were found, in 6 apiaries, but only 2 of the apiaries were close to the new beekeeper's apiaries.
The established beekeeper decided to continue to use the apiary quarantine on all apiaries during honey production, with all boxes returning to their respective apiaries. Approximately 200 new boxes with foundation were produced and used to supplement apiaries where the honey production was greater than the available store of boxes for the apiary.
No new cases of AFB were found that autumn, but 4 diseased hives in 2 apiaries were found the following spring. The beekeeper reduced the apiary quarantine to boxes from those two apiaries, but still marked all boxes to all apiaries when the honey was taken off. No new cases were found in the next three seasons.
The established beekeeper still uses the post-honey crop apiary quarantine as a matter of routine, however, releasing boxes into the general pool of honey supers only once the spring inspection rounds have been completed and the honey boxes are about to put on the hives.
This case study demonstrates that AFB elimination in outfits is quite possible, and for extended periods of time, especially if there are no major hive movements in the outfit, and the beekeeper has undisturbed use of a production area. However, the growth of beekeeping in New Zealand has meant that most areas are now more extensively utilised than in the past, and as a result there is a greater chance of AFB outbreaks occurring, especially when new beekeepers do not concentrate on AFB inspection and disease control.
The case study also shows how an apiary quarantine can be an effective means of dealing with an AFB outbreak.
Type - Pollination and Honey Production
The beekeeper in this case study runs a very intensive management system. Hives are stimulated in the spring, and when they become too big to make normal-sized pollination units (ie., they are not able to fit comfortably into two storeys), splits are created, using surplus brood and bees from several colonies to make up the new hive.
Beekeepers often comment that AFB will show up later in splits, even though no visual symptoms of AFB could be found in the parent colonies at the time the split was made. Although the phenomena has so far not been investigated in controlled trials, what has been suggested is that spores are present in the parent colonies. However, due to the colony's population size and number of house-cleaning bees, the colony is managing to remove and destroy AFB infected larvae/pupae before they show any visual signs of the disease.
When a split is made, the population of the hive is reduced, and the house-cleaning bees are not evenly distributed between the split and the parent hive. As a result, one of the halves of the split begins to show visual signs of AFB, while the other appears to remain free of AFB.
Having experienced this phenomena, and wanting to keep track of the brood and bees used to make splits, the beekeeper in this case study devised a recording system that was based on how orders are taken for food in a take-away bar. The system works like this:
This case study utilises another form of hive quarantine. Equipment is swapped between hives, but the movement of the equipment is recorded. The method is only recommended in outfits with low levels of AFB. In outbreak situations, a better policy would be not to move any equipment between hives.
Type - Pollination and Honey Production
The beekeeper in this case study employs staff to carry out field work, and concentrates instead on honey packing and customer relations. The outfit has always had a low level of AFB incidence. Because the beekeeper felt the situation was under control, not much emphasis was placed on AFB inspection. Staff were instructed to only look at 3 brood frames during inspection. Inspections were confined to once in the spring, and once in the autumn.
One year, after AFB was found in over 15% of the hives in several apiaries, the beekeeper decided to do an analysis of AFB findings over the previous 5 years. To the beekeeper's surprise, the incidence of AFB in the outfit was steadily increasing, from just under 1% at the beginning of the period to just under 5% at the end.
The beekeeper met with staff and discussed the current inspection routine. It was decided that all hives from now on would receive full brood inspections, and that the number of inspections would increase to 3 in the spring and 2 in the autumn. The beekeeper also gave staff further training in identifying AFB symptoms.
The beekeeper kept close track of AFB incidence in the next 3 years. In the first year, the incidence actually rose to almost 6%. In the next year, however, the incidence dropped to about 2.5%, and in the following year, it had returned to just under 1%.
The case study demonstrates that changes in the level and frequency of AFB inspection can make a significant difference to AFB levels, particularly in large outfits where disease levels are rising. The study also shows how important it can be to do annual calculations of AFB incidence, since these calculations provide a objective measure of the effect of management changes on AFB levels.
Type - Honey
The beekeeper in this case study decided to purchase a beekeeping outfit with a known AFB problem, and as a result instituted an intensive disease control programme comprising several different elements.
The first element was hygiene, in and between the apiaries. The beekeeper believed that 90% of AFB is spread by the beekeeper, so after finding a diseased hive, and whenever work was finished in an apiary, gloves and smoker were washed with detergent and water, and the hive tool was scorched with a propane burner.
The second element was record keeping. The beekeeper kept a diary for every apiary and recorded what happened to the hives at each visit.
The third element is what the beekeeper called the "Elimination System". According to the beekeeper, the ultimate would be to put all honey supers back on the same hives they were taken from the previous season. However, the beekeeper didn't consider this was practical because of the number of hives in the outfit, so the beekeeper developed a grading scheme for the apiaries instead. This scheme had four grades:
The first year, the beekeeper had composite bee samples from each apiary tested for AFB spores. Apiaries that showed no AFB were put into Grade 0. Apiaries that returned 1 to 10 AFB colonies per plate were put into Grade 1, while 10 to 30 colonies per plate went into Grade 2, and above 30 colonies per plate went into Grade 3.
Once the grading was completed, the following management practices were implemented:
When the beekeeper started the programme, the outfit had an 8% AFB incidence. After one year, the figure dropped to 7%. The next year, the figure dropped to 5%, and a pattern began to emerge. Instead of disease appearing throughout the outfit, AFB was confined to certain apiaries. By year 3, the disease level was down to 3.5%, with AFB only found in a few apiaries.
The beekeeper is currently in the fourth year of this programme. Although disease figures are only available for the first half of the year, the situation looks very encouraging, with a predicted disease level of around 2% for the full year.
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