Grey Mould (Botrytis) on Strawberry and Tomato: Organic Control

Grey mould (Botrytis cinerea) is recognisable by its grey, fluffy, powdery coating. One of the widest-ranging pathogenic fungi in the organic garden — affects strawberries, tomatoes, raspberries, grapes and salad crops. Particularly dangerous during flowering and before harvest when soft fruit is most vulnerable.

15–25°C temperature and high humidity. Fallen flower petals provide a breeding ground during flowering. Rainy, damp weather accelerates infection. Particularly dangerous before harvest when fruits are soft and easily damaged. Poor airflow and dense planting increase infection risk.

Ensure good airflow and do not plant too densely. For strawberries, use straw mulch to keep fruits off soil. Never water in the evening — keep foliage dry. Collect fallen flower petals during flowering. Remove rotting or damaged fruit immediately. These practices dramatically reduce grey mould pressure.

Trichoderma harzianum — a permitted organic antagonist fungus that directly displaces Botrytis. Bacillus subtilis (Serenade-type products) is most effective preventively. Bordeaux mixture applied before flowering reduces infection. Remove infected parts immediately and do not compost — dispose in trash to prevent spread.