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Botrytis Grey Mold
- Young infected leaves first appear as brown with blighted areas, often V-shaped, that progress up the petiole and into the stem.
- Gray-brown velvety mycelia grow on the leaves or stems.
- The stems turn white and develop cankers.
- Infected stems girdle and wilt.
- Gray conidiophores producing conidia cover the dying flowers and the calyx of the fruit.
- Mycelium spreads from the flowers to the fruit and back toward the stem.
- Fruits may also develop ghost spots, or necrotic flecks surrounded by whitish halos.
- Fruit also decay and turn light brown or gray and begin to rot.
- Grey mold may be visible on the fruit calyx.
A cloud of grayish-white conidia are observed on all infected plant parts when the disease has progressed. A hand lens will reveal conidiophores producing conidia resembling a bunch of grapes. Under a microscope, the mycelium will produce branching tree-like conidiophores.
Often Confused With
- Sclerotinia white mold – Infected stems become bleached and are covered with a very fuzzy white mycelium. This mycelium can spread to flowers and other parts of the plant, similar to botrytis grey mold.
- Rhizopus rot – Mycelia growth is black and very fuzzy, resembling that produced by Botrytis cinerea. Severe infection on the fruit becomes rotted, but unlike botrytis grey mold, the fruit also becomes tough, dried, and mummified.
- Botrytis selective medium is a semi-selective for Botrytis sp.