Ascosphaera apis

Definition

A cosmopolitan ascomycete fungus (family Ascosphaeraceae) and obligate entomopathogen of honey bees (Apis spp.), causing chalkbrood disease in larvae. The fungus produces distinctive dark, thick-walled ascospores within cyst-like ascomata (spore cysts) that accumulate as chalky mummies in brood cells. Infection occurs when larvae ingest spores; germination is triggered by gut conditions, with hyphae penetrating the gut wall and colonizing tissues. The species was among the first entomopathogen genomes sequenced, providing insights into host-specific pathogenesis and spore dormancy strategies.

Etymology

From Greek askos (bladder, sac) + sphaira (sphere, ball), referring to the spherical spore cysts; apis (Latin: bee), indicating its host association with honey bees.

Example

In apiary management, Ascosphaera apis spores can persist for years in comb wax and woodenware; requeening with chalkbrood-resistant stock and maintaining strong colonies with adequate ventilation are primary non-chemical control strategies.

Synonyms

• chalkbrood fungus
• honey bee chalkbrood pathogen

Related Terms

• chalkbrood disease
• entomopathogenic fungus
• Ascosphaerales
• Apis mellifera
• brood disease
• ascospore
• mummy (honey bee)

Usage Notes

The species name is often used interchangeably with the disease name "chalkbrood" in beekeeping contexts, though chalkbrood refers specifically to the pathological condition. Ascosphaera apis is host-specific to Apis species and does not infect other insects. Spore morphology (dark, punctate ascospores in spherical cysts) distinguishes it from the less common Ascosphaera major, which produces larger spores and primarily affects the alfalfa leafcutting bee (Megachile rotundata).