Disease: Grey mould – Botrytis cinerea, though other species may cause similar symptoms.
Importance: Common nursery pathogen
Symptoms: Include blights, spots, blotches, wilts, cankers, rots, damping off and storage diseases. Usually the softer tissues such as petals are blighted, though leaf spotting, stem blights and rotting of cuttings and seed occur, especially in crowded situations. Early symptoms are small spots, which can extend into large areas of blight and later the characteristic grey mould comprised of masses of spores, which mostly become air-borne. Botrytis can affect plants at different stages of their life from seeds, bulbs and cuttings through to mature plants.
Transmission: Masses of air-borne spores are produced which are spread by wind, water splash, insects such as bees and aphids and handling of infected material. Spores can also be carried on seed, cuttings, seedlings and bulbs. The spores need moisture for germination and infection.
Favoured by: Cool, wet weather conditions when temperatures are below 25oC (optimum temperatures are 18o – 23oC). Closed growing areas where humidity is high suit Botrytis infections. Autumn and spring overcast days and shorter day lengths are also favoured.
Host range: Very wide. Some species (such as lisianthus and cyclamen) are extremely susceptible.
An initiative of the Nursery Levy funded National Nursery Industry Biosecurity Program and ‘Building the resilience and on-farm biosecurity capacity of the Australian production nursery industry’ Project