2.9. May disease
May disease is not an infectious disease, but a metabolic disorder that mainly occurs in spring when the brood is developing rapidly. It is linked to a lack of water in the colony. The following information is based on official memo 2.9 from the Swiss Bee Health Service.
Official Practical Guide – Summary
Practical Guide: 2.9 May Disease
- Cause: May disease results from a water deficit combined with high laying activity.
- Characteristic signs:
- Bees crawling and unable to fly in front of the hive.
- Distended abdomen.
- Reduced flight activity.
- Contributing factors:
- Cold weather conditions limiting water foraging.
- Insufficient availability of water sources.
- Extensive brood development.
- Management:
- Provide an easily accessible water source.
- Improve apiary conditions.
- Monitor the development of the situation.
- Important note:
- May disease is not contagious and generally resolves quickly once conditions are corrected.
► Open the practical guide PDF directly (FR)
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Summary compiled on the basis of Practical Guide 2.9. Last verified: 01/2026.
See also:
- What water for our bees?
- Practical Guide: 4.9 Choice of Location
- Practical Guide: 4.8.1 Hive Entrance Observation
- Practical Guide: 4.7.3 Recognising Healthy Colonies
- Recognising Bee Diseases
- Water Collection and Storage
