Beesfor Development Journal 78
CHALK BROOD IN ETHIOPIA
Desalegn Begna Rundassa, Holetta Bee Research Centre, Ethiopia Table 1. Comparison between the standard size set for Ascosphaera apis spore cysts and balls, and the microscopic measurement after laboratory culturing
Chalk brood is a disease of honeybee larvae caused by the fungus Ascosphaera apis, which causes the death and mummification of sealed honeybee brood, and with the consequent weakness of the colony. It is widespread amongst honeybees in Europe and North America. In Africa the only report of chalk brood has been from Tunisia (Heath, 1985). The disease is spread by robbing, drifting bees and by the normal practices of beekeeping (Warhurst, 1998). Ascosphaera apis produces sticky spores, which are commonly present on adult bees and all surfaces within occupied hives. The disease develops only if the brood is physiologically stressed in some way, for example chilling.
Parts measured Spore cysts Spore balls
Standard range 45-119µ 7-18µ
Measurement taken from the culture 40-89µ 7.2-17.8µ
Table 2. Total number of colonies diagnosed, number of colonies found positive, and percentage infestation per inspected site
In Ethiopia, the existence of two adult honeybee diseases Nosema apis and Melpighamoebae mellifica and their distribution was studied and reported (Gezahegn & Amsalu, 1991; Desalegn & Amsalu, 1999). Until now there has been no record on the existence of any honeybee brood diseases in the country.
Site Number
Apiary site
1
Holetta
36
5
13.9
2
Menagedha
54
17
31.5
The survey transects and beekeepers to be surveyed were selected randomly. A survey was carried out around the Holetta area on beekeeper's colonies, and at Gedo demonstration site about 150 km west of Holetta.
3
Gedo
16
5
3.2
4
Suba
42
0
0.0
5
Geresu
18
0
0.0
Following the brood rearing season October 2000 to January 2001, 276 colonies at 13 survey sites were inspected externally and internally for signs of chalk brood disease.
6
Sadamo
14
3
21.4
7
Roge
25
0
0.0
8
Rob Gebeya
24
0
0.0
Colonies showing any symptoms of chalk brood: dead infected larvae left uncapped by nurse bees in the comb cells, and mummies at the hive entrances, on the hive floor and on the ground perpendicular to the hive opening, were examined. From 13 apiary sites, larval mummies were collected from eight apiaries that were found to display positive signs of the disease. Overall 240 black mummies of honeybee larvae from 48 bee colonies (five per colony) were collected. Each mummy was macerated separately in a sterile mortar with distilled water to prepare suspensions containing Ascosphaera apis from each site. The suspensions were filtered through fine cloth and the fungus was grown in the laboratory, using Potato Dextrose Agar containing antibiotic to avoid any bacterial contamination, on petri dishes. After eight days, microscopic examination of the cultures was made to determine the size of the spore cysts and spore balls (Skou, 1972; Bailey, 1981, Bissett, 1988). Photographs were taken of the affected brood combs and fungus cultures.
9
Gelgel
5
0
0.0
10
Shola Genet
29
6
20.7
11
Tesfaye
4
4
100.0
12
Chiri
1
1
100.0
13
Mariam
8
7
87.5
276
48
Materials and methods
Total
Number of inspected colonies
Number of infected colonies
% infected colonies per apiary site
Chalk brood disease is most commonly found on the outer fringes of the brood combs and as a result drone brood is more susceptible to the disease. In this survey it was noticed that drone brood rearing was completely discontinued in the colonies seriously affected by chalk brood disease. The dismantling and clearing of the drone larvae and pupae by the bees was observed in the affected colonies. The assumption is that the bees give priority to nursing and warming brood that will grow into worker bees as a replacement stock rather than taking care of drone brood for breeding in these adverse conditions. Gochnauer et al (1975) also documented that when the colony clusters due to cool temperatures, the population of adult bees is insufficient to maintain ideal brood temperatures, particularly on the periphery of the brood. Thus, chalk brood disease is most likely to appear in brood unprotected by the cluster, which usually includes the drones. Since this survey report many complaints about chalk brood have come from different apiaries at the Centre and from farmer beekeepers.
Results Microscopic examination of the culture revealed that the range of the size of the spore cysts and the spore balls falls within the standard size described for Ascosphaera apis by Spiltoir and Olive (1955). From 13 inspected apiaries, eight (66.7%) were found positive to Ascosphaera apis (Table 2). Out of 276 inspected colonies, 48 (17.4%) were found tainted with chalk brood fungus. The prevalence of the fungus among the infected apiary sites ranged from 0-100%. All colonies infested with chalk brood fungus Ascosphaera apis have revealed the signs of the disease either externally or internally. The disease was particularly rigorous and widely distributed in the apiaries of Tesfaye and Mariam (Table 2), which are owned by private farmer beekeepers and within 5-10 km from Holetta Centre. During the survey it was observed that much of the affected brood was drone brood, during October.
References BAILEY, L. (1981) Honeybee pathology. Academic Press, London, UK. pp: 40-44. 924/73. BISSETT, J. (1988) Contribution towards a monograph of the genus Ascospaera. Canadian Journal of Botany 66: 2541-2560. 1314/82. DESALEGN, B.; AMSALU, B. (1999) Distribution of honeybee diseases Nosema apis and Melpighamoebae mellificae in Ethiopia. Holetta Bee Research Centre Annual Report. GEZAHEGN, T. AMSALU, B. (1991) Identifying and diagnosing honeybee diseases at Holetta Bee Research and Training Centre. Proceedings of the Fourth National Livestock Improvement Conference. pp: 263-265. GOCHNAUER, T. A.; FURGALA, B. SHIMANUKI, H. (1975) Disease and enemies of the honeybee. In: The Hive and the honeybee. Dadant & Sons, Illinois, USA. HEATH, L.A.F. (1985). Occurrence and distribution of chalk brood disease of honeybees. Bee World 66 (1): 9-15. SKOU, J.P. (1972) Ascosphaerales. Friesia 10(1): 1-24. 13/74. SPILTOIR, C.F.; OLIVE, L.S. (1955) A reclassification of the genus pericystis Betts. Mycologia 47: 238-244. WARHURST, P. (1998) Beekeeping disease: correct diagnosis. Department of Primary Industries, Queensland Government, Australia.
Discussion and conclusion Since the beginning of 2001, the presence of Ascosphaera apis has been confirmed in Ethiopia. However, as the main objective of this study was only to detect the presence of chalk brood in the country for the first time, no attention was given to compare its infestation level among colonies in the same apiary. Also, no attempt was made to compare colony infestation level at different apiaries. Diseases of fungal origin are more prevalent in damp and cool conditions and Ascosphaera apis grows best when the brood is chilled. In this case many of the incidences were in October, when the temperature sometimes drops below 0°C. 8
