Spotting European foulbrood (EFB), caused by the bacterium Melissococcus plutonius, involves looking for an uneven "pepper-pot" brood pattern, discolored and twisted larvae lying unnaturally in open cells, and a mild sour odor. It typically attacks unsealed brood, causing larvae to starve, die, and dry into rubbery scales.
Key Signs of EFB
- Larval Changes: Larvae turn from pearly white to yellow, then brown, often showing distinct visible tracheal (breathing) tubes through their skin.
- Abnormal Position: Instead of a neat curled "C" shape at the base of the cell, sick larvae twist and slump unnaturally against the walls or bottom.
- Brood Pattern: The comb looks spotty or patchy because hygienic bees constantly clean out the dead, dying larvae.
- No Ropiness: Unlike American foulbrood, EFB remains watery or pasty and generally does not stretch into a long, sticky "rope" when tested with a stick.
- Scales: Dried remains turn into a rubbery, easily removable brown scale rather than sticking hard to the cell wall.