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Resistance to Chalkbrood disease in Apis mellifera L. (Hymenoptera: Apidae) colonies with different hygienic
C Invernizzi1, F Rivas, L Bettucci
1Sección Etología, Facultad de Ciencias, Montevideo, Uruguay. ciro@fcien.edu.uy
Abstract:
Chalkbrood disease affects the larvae of honeybees Apis mellifera L. and is caused by the fungus Ascosphaera apis. Infected larvae die when they are stretched in the cap cell and suffer a gradual hardening that ends in a very hard structure (mummie). Several studies have demonstrated that colonies that express an efficient hygienic behaviour (uncapping of cell and subsequent removal of dead brood) exhibit a higher resistance to the disease. However, it remains unclear whether the advantage of hygienic colonies over less hygienic ones lies in the ability to remove mummies or in the early detection of infected larvae and its cannibalization before they harden. To elucidate this aspect, the hygienic behaviour of 24 colonies, which were subsequently provided with pollen cakes containig A. apis, was evaluated. The number of mummies and the number of partially cannibalized and whole larvae in uncapped cells were recorded. The most hygienic colonies controlled the disease better. These colonies also had a higher tendency to uncap cells that contained infected larvae and cannibalize them. The presence of A. apis in partially cannibalized and whole larvae in uncapped cells indicate that the advantage of hygienic colonies over less hygienic ones lies in the early detection of infected larvae death and their quick removal from the cell before they become mummies.
Insights
Hygienic honeybee colonies better control chalkbrood disease by detecting and removing infected larvae early, preventing mummy formation. This early intervention is key to colony resistance against Ascosphaera apis.
Area of Science:
- Apiculture
- Insect Pathology
- Animal Behavior
Background:
- Chalkbrood disease, caused by Ascosphaera apis, impacts honeybee (Apis mellifera L.) larvae.
- Colonies with efficient hygienic behavior show increased resistance to chalkbrood.
- The precise mechanism of this resistance (mummy removal vs. early detection) is unclear.
Purpose of the Study:
- To determine if hygienic honeybee colonies control chalkbrood disease through early detection and removal of infected larvae or by removing hardened mummies.
- To elucidate the role of larval cannibalization in disease resistance.
Main Methods:
- Evaluated the hygienic behavior of 24 honeybee colonies.
- Artificially infected colonies with Ascosphaera apis via pollen cakes.
- Quantified mummies and partially or wholly cannibalized larvae in uncapped cells.
Main Results:
- Highly hygienic colonies demonstrated superior control over chalkbrood disease.
- These colonies exhibited a greater tendency to uncap cells with infected larvae and cannibalize them.
- Ascosphaera apis was detected in partially cannibalized and whole larvae, indicating early removal.
Conclusions:
- The advantage of hygienic honeybee colonies in combating chalkbrood lies in the early detection and removal of infected larvae before they develop into mummies.
- Early larval cannibalization is a critical component of hygienic behavior for disease resistance.
