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by Michael Hornitzky
May 2005
RIRDC Publication No 05/055 RIRDC Project No DAN-228A
Executive summary
Nosema apis is a serious
parasite of adult honey bees. It has been reported to cause significant
production losses as a result of a range of effects it has on adult bee
longevity, queen bees, brood rearing, bee biochemistry, pollen collection
and other bee behaviour. Despite these effects there are no classic signs
of infection and hence most infections are unrecognised.
The aim of this project was to increase the awareness of the beekeeping industry to this serious infection. This was achieved by preparing a literature review that provides information on the effects of the disease, current control methods and the laboratory diagnosis of the infection. The laboratory diagnosis can be carried out by beekeepers so that they can monitor Nosema levels and apply appropriate management strategies to minimise infection levels.
There is very little published information on the prevalence and significance of N. apis in Australian honey bees. The second part of this study was a quantitative survey of 800 honey bee colonies at Robinvale, Victoria for N. apis. The colonies owned by 20 beekeepers from New South Wales, Victoria and South Australia were congregated in one area for almond tree pollination and provided a unique opportunity to sample colonies from diverse origins.
This survey provided good data on the prevalence of Nosema spores in Australia. There was a broad range of infection levels ranging from 10,000 to 12,236,000 spores per bee. This range suggested that some beekeepers were better able to control nosema disease than others, although they were probably not aware what impact these practices were having on N. apis levels. Analysis of the completed questionnaires that were filled in by the beekeepers that took part in the survey indicated likely management strategies to control N. apis.
These were (i) packing of hives down tight for the winter, (ii) no manipulation of hives during the winter (including no supplementary feeding of individual hives), (iii) no shifting of bees during the winter and (iv) hives with low Nosema levels were mostly ¾ to full of honey. A survey of the same hives will be carried out at the same time of next season to determine whether these factors continue to remain important in minimising the effects of N. apis. More details of hive location and management prior to the survey will also be determined.
This work has demonstrated that nosema disease is common in Australian honey bee colonies and that further work should be carried to determine what impact this disease has on the beekeeping industry in Australia.
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