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Botrytis

Practical biological control, IPM and environmental pest-management knowledge.

Botrytis

Botrytis cinerea is a common fungal disease affecting flowers, fruit, leaves and soft plant tissue. It is often called grey mould because infected tissue can develop a grey-brown fuzzy spore layer under humid conditions.

Botrytis is mainly a disease of weak, damaged, senescing or wet tissue. Flowers, soft fruit, pruning wounds, damaged leaves and dense canopy areas are especially vulnerable.

Description

Botrytis often begins on dead or ageing tissue before spreading into healthy tissue nearby. In crops such as strawberries, ornamentals, soft fruit and protected crops, it can affect flowers, fruit, stems and leaves.

Typical symptoms include:

  • Pale brown or grey lesions
  • Soft rot on flowers or fruit
  • Grey mould growth in humid conditions
  • Infection starting around old petals or damaged tissue
  • Collapse of soft plant parts under prolonged wetness

Environmental drivers

Botrytis risk increases when plant surfaces stay wet for long periods.

Key drivers include:

  • High relative humidity, especially above 85–90%
  • Condensation on leaves, flowers or fruit
  • Poor airflow in dense canopies
  • Wet flowers or fruit after rain or overhead irrigation
  • Mild temperatures, often around 10–22°C
  • Dead petals, old leaves or crop debris left in the canopy
  • Slow drying overnight or in shaded areas

Botrytis does not always need heavy rain. A humid, still canopy with condensation can be enough to create infection risk.

Weather risk signals

Botrytis pressure is more likely when:

  • Rain is forecast
  • RH is high
  • VPD is low
  • Air movement is poor
  • The crop has flowers, soft fruit or damaged tissue present

Management principles

Botrytis management is mostly about reducing wetness duration and removing infection sources.

Useful cultural actions include:

  • Improve airflow through spacing and canopy management
  • Remove dead flowers, old leaves and infected material
  • Avoid prolonged wet foliage
  • Irrigate early enough for plants to dry before night
  • Reduce dense, shaded, stagnant crop areas
  • Handle fruit and flowers carefully to avoid wounds
  • Monitor high-risk areas after wet or humid periods

Biopredator weather link

The Biopredator weather tool flags Botrytis risk when mild temperatures combine with high humidity, rainfall or slow-drying conditions.