Gray Mold

Gray mold is identified by a fuzzy, grey to brown fungal growth that develops on decaying or infected flowers, fruit, stems, and leaves, often starting at wounds, faded flower parts, or where plant surfaces touch. Infected tissue typically becomes soft, water-soaked, and brown before the characteristic grey spore layer appears.

Botrytis cinerea produces huge numbers of airborne conidia (asexual spores) on infected tissue, which are dispersed by wind and water splash to new hosts. The fungus is an efficient necrotroph, often entering through wounds, dead or senescing tissue such as spent flower petals, or areas of high humidity where plant parts touch, before spreading into adjacent healthy tissue.

• Survives between seasons as resting structures (sclerotia) or as mycelium in plant debris
• Infection is strongly favoured by free moisture and moderate, cool temperatures
• Can continue to develop after harvest, making storage and transit conditions important

Grapevine, strawberry, and tomato are among the crops most affected by gray mold, but its host range extends to a very wide range of vegetables, fruits, and ornamentals. On grape it causes bunch rot of ripening clusters; on strawberry it rots flowers and fruit; and on tomato it can blight flowers, stems, and fruit, particularly in humid greenhouse production.

• Cool, humid conditions with prolonged leaf, flower, or fruit wetness
• Dense canopies and poor air circulation, especially in greenhouses and tunnels
• Wounds from handling, insects, or weather, and senescent tissue such as spent flowers
• Excessive nitrogen supply producing soft, lush growth
• Fruit clusters or plants in close contact, allowing the fungus to spread between touching tissue

Because Botrytis cinerea readily colonises wounded or senescent tissue and spreads rapidly in humid conditions, management focuses on reducing humidity and injury, removing infection sources, and inspecting produce regularly.

• Improve air movement through spacing, pruning, and canopy management
• Remove spent flowers, damaged fruit, and infected debris promptly
• Avoid excessive nitrogen and overly dense plantings
• Handle fruit carefully to minimise wounds, and manage storage humidity and temperature
• Scout regularly, especially during cool, humid weather or in enclosed production systems