Grey mold

Botrytis cinerea is a necrotrophic fungus and the primary agent of grey mold disease. It belongs to the phylum Ascomycota and is notorious for its broad host range, affecting fruits, vegetables, and ornamental plants worldwide. Its ability to survive on decaying organic matter makes it a persistent threat in both field and greenhouse environments.

The hallmark symptom of the disease is the development of a fuzzy, grey mycelial mat on infected plant tissues. This growth consists of millions of conidia that facilitate rapid spread. Infected fruits and blossoms develop soft, watery rot, which eventually leads to complete destruction of the harvested plant material. Leaves and stems can also suffer from necrotic lesions that can girdle the plant, causing wilting.

The life cycle is characterized by the production of resistant structures called sclerotia, which allow the fungus to overwinter in soil or plant debris. Upon germination, the fungus produces spores (conidia) that spread via wind, splashing water, and mechanical handling. The pathogen often enters through wounds or natural openings such as stomata or hydathodes.

Development and spread are heavily dependent on environmental conditions, specifically high relative humidity (above 90%) and cool to moderate temperatures. Dense crop canopies, poor ventilation, and the presence of free water on plant surfaces significantly increase the risk of an outbreak. The fungus is opportunistic and aggressively colonizes tissues stressed by environmental factors or injury.

Integrated Pest Management (IPM) is essential for effective control of grey mold:

• sanitation practices to remove potential inoculum sources;
• maintaining low humidity through pruning and adequate spacing;
• avoiding overhead irrigation to keep plant surfaces dry;
• application of preventative and curative fungicides at critical growth stages;
• utilization of biocontrol agents such as Bacillus subtilis or Trichoderma species.