Nosema in honey bees requires looking for external signs like fecal streaking on the hive entrance or a slow buildup in spring, but a definitive diagnosis requires a microscope.
External Signs in the Apiary
- Fecal spotting: Yellow, brown, or dark streaks of dysentery on the front of the hive, landing board, or frames (Nosema apis).
- Crawling bees: Sluggish or trembling bees unable to fly, sometimes with bloated or greasy-looking abdomens, often found crawling near the entrance.
- Spring dwindling: A weak colony population that fails to grow in spring despite having plenty of stored honey and pollen.
- Silent infections: Note that Nosema ceranae often shows no visible dysentery or outward signs other than a gradual weakening and shortening of adult bee lifespans.