MICROBIOLOGICAL STUDIES ON CHALK-BROOD DISEASE IN HONEYBEE COLONIES IN EGYPT

Document Type : Original Article

Authors

1 Agricultural Microbiology Dept., Fac. of Agrlc., Cairo Univ., Giza.

2 Department of Economic Entomology, Fac. of Agric., Cairo Univ., Giza.

3 Bee Division, Plant Protection Institute, ARC, Giza.

Abstract

Chalk-brood disease in honeybee larvae, caused by the heterothallic fungus
Ascosphaera ap < /em>is, was recently diagnosed in Egypt in 1995 and is regarded lately as a
threat to the Egyptian honeybee keeping. Effective control of such disease is currently
unavailable all over the world, and the most common practice is to re-queen from
different genetic stocks. This work was undertaken to study some morphological,
cultural and physiological characteristics of Ascosphaera ap < /em>is isolated from honeybee
colonies in Egypt. Microorganisms associated with chalk-brood mummified honeybee
larvae were also examined using different culture media. The results showed that A.
apis was the most prevalent fungus in chalk-brood mummified larvae, representing
33.3% of the isolated microorganisms from all the examined media followed by
Aspergillus. fumigatus (27.4%) and Aspergillus flavus (14.1%). Bacteria and yeasts
represented 12.6 and 10.6% of the total number of microorganisms isolated from
mummified larvae, respectively. Potato Dextrose yeast Agar was the most proper
medium for isolation, cultivation and characterization of this fungus followed by malt
Agar and Saboruad's Agar. The antifungal activities of essential oils from sweet
marjoram (Majorana hortensis), basil (Osinum basilicum), peppermint (Mentha peprita)
and spearmint (Mentha viridis) against A. apis were examined, both in vitro and in vivo.
Marjoram and peppermint oils were the most effective against growth in vitro of the
fungus. Feeding honeybees with sugar syrup containing 0.5 or 1 % of marjoram oil
resulted in reductions in the percentages of chalk-brood mummies comparable to those
obtained with application of 40% formic acid solution. Screening of some
microorganisms for antibiosis towards A. ap < /em>is showed that Bacillus spp < /em>. (CHBr),
isolated from mummified honeybee larvae, was the most potent antagonistic candidate
compared to the other examined microorganisms. Preliminary investigation of in vivo
antagonistic capabilities of this bacterium suggested a possible integration of such
bioagent along with sweet mariorarn essential oil into a management strategy for
chalk-brood biological control.

Keywords

Journal of Plant Protection and Pathology
Volume 30, Issue 11
November 2005
Pages 7089-7102

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