Botrytis Blight (Gray Mold)

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Botrytis Blight (Gray Mold)

  •  Caused by the fungus Botrytis cinerea, a necrotrophic pathogen, meaning it kills host tissue to feed on it
  •   Botrytis cinerea has a broad host range, affecting over 200 plant species, including grapes, strawberries, tomatoes, lettuce, beans, roses, and many ornamental plants.


    •   Domain: Eukaryota
    •   Kingdom: Fungi
    •   Phylum: Ascomycota
    •   Subphylum: Pezizomycotina
    •   Class: Leotiomycetes
    •   Order: Helotiales
    •   Family: Sclerotiniaceae
    •   Genus: Botrytis
    •   Species: Botrytis cinerea

 Disease Cycle:

  • Spores: Botrytis cinerea produces spores (conidia) that are easily dispersed by wind, water, and physical contact. These spores land on plant surfaces and require moisture for germination.
  • Infection: The fungus infects plant tissues through wounds, cuts, or natural openings like stomata. It can also invade healthy tissue under prolonged wet conditions.
  • Environmental Conditions: Cool, humid, and wet conditions favor the spread and development of gray mold. Greenhouses and densely planted crops are particularly susceptible due to poor air circulation.

Symptoms:

  • Leaf Spots and Blight: Brown or gray spots on leaves, which may expand and cause the leaves to wither and die.
  • Flower Blight: Infected flowers develop water-soaked lesions and may turn brown and collapse.
  • Fruit Rot: Gray mold often develops on mature fruits, producing a soft rot, especially on grapes, strawberries, and tomatoes.
  • Stem Cankers: Infected stems may develop dark, sunken cankers, leading to plant wilting.
  • Gray Fungal Growth: In high humidity, a characteristic fuzzy gray mold may appear on affected tissues, particularly fruit, flowers, or leaves.

Management Strategies:

  • Cultural Controls:
    • Reduce humidity by improving air circulation and spacing plants properly.
    • Avoid overhead watering to keep plant foliage dry.
    • Prune and remove infected or dead plant material to reduce fungal inoculum.
    • Improve drainage and avoid waterlogged conditions around plants.
  • Chemical Control:
    • Fungicides can be applied preventively or early in the infection cycle, especially during favorable weather conditions.
    • Rotating fungicides to avoid resistance development is important, as Botrytis cinerea can develop resistance to chemical treatments.
  • Biological Control:
    • Certain biocontrol agents, such as Trichoderma species, are used to suppress Botrytis cinerea in some settings.
  •  Sanitation:
    • Remove and destroy infected plant material and debris from the growing area to minimize the source of spores.
  •   Resistant Varieties:
    • Planting resistant cultivars, when available, can help reduce susceptibility to gray mold.

 

 

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