The Pervasive Fungal Threat: Botrytis cinerea spores are ubiquitous in the atmosphere. Fungal infection occurs whenever moisture, moderate temperatures, and susceptible plant tissue coincide. Prevention relies on eliminating free moisture and keeping storage temperatures cold.
1. Recognizing Botrytis Symptoms
Botrytis enters floral tissues through micro-abrasions, trimming wounds, and natural stomata:
- Petal Spotting: Water-soaked, brown softened lesions on dark-coloured petals (especially red, pink, and purple varieties).
- Specking on Roses: Tiny circular white-to-tan flecks across rose petals that rapidly expand into sunken lesions.
- Foliage Defoliation: Rapid yellowing, browning, and premature leaf drop along the upper stem.
- Fuzzy Grey Mould: In the advanced reproductive stage, spores form a characteristic velvety grey fuzz that easily disperses airborne into nearby stock.
2. Temperature & Humidity Parameters
Botrytis spores cannot germinate without liquid water. Temperature management and dew point control are critical:
Core Coolroom Environmental Rules:
- Keep Temperatures ≤ 3°C (38°F): Colder storage (0°C – 2°C) severely restricts fungal development and spore germination.
- High Relative Humidity Without Free Water: Maintain high relative humidity (approx. 90%) to prevent dehydration, but never allow condensation to form on petal surfaces.
- Avoid Sudden Temperature Swings: Moving flowers rapidly from a cold coolroom to warm humid air causes immediate condensation (dew point sweat), triggering instant spore germination.
3. Airflow and Packaging Practices
- Keep Coolrooms Ventilated: Consistent gentle air movement prevents static pockets of moist air from stagnating around flower heads.
- Loosen Bunches: Pack bunches loosely in buckets. Overcrowded buckets trap transpiration moisture between adjacent blooms.
- Never Pack Wet Flowers: Never carton or pack flowers cut during morning dew or rain without thoroughly drying petals first.
4. Rigorous Sanitation Procedures
Even if flowers arrive perfectly healthy from the farm, they can be contaminated in wholesale floors or florists by spores lingering in dirty buckets or coolroom floors.
- Wash buckets after every turn with a dedicated quaternary ammonium biocide or bleach disinfectant (e.g. Snow White).
- Sweep and wash coolroom floors weekly; remove all dropped leaves and petals immediately.
- Strict Stock Rotation: Implement strict First-In, First-Out (FIFO) stock rotation so batches never sit in cold storage longer than necessary.
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