How To Deal With Grey mould (botrytis on ornamentals) in Your Irish Garden
What is Grey mould (botrytis on ornamentals)?
Grey mould on ornamental plants is caused by the ubiquitous fungus Botrytis cinerea, the same pathogen that affects fruit and vegetables. On ornamental plants, it is particularly damaging to flowers, bulbs and soft-stemmed plants grown under glass or in damp, sheltered conditions. Botrytis attacks dead and dying tissue first, then spreads into living plant parts. The disease is characterised by fluffy grey-brown fungal growth on affected tissue, often accompanied by a cloud of spores when disturbed. It is most problematic on cyclamen, begonias, chrysanthemums, geraniums, African violets and many bedding plants, particularly during autumn and winter when conditions are cool and humid.
Damage Caused by Grey mould (botrytis on ornamentals)
Grey mould causes a fuzzy grey-brown fungal growth on flowers, leaves and stems of ornamental plants. Flowers develop brown spots that enlarge and become covered with grey spore masses. Stems rot at the base, causing whole plants to collapse. Bulbs rot in storage, with a grey furry coating developing on the surface. Cyclamen are particularly susceptible, with the crown rotting and the plant collapsing. Overwintering geraniums lose stems to grey mould. In greenhouses, the disease can spread rapidly among closely spaced plants in cool, humid conditions.
How to Prevent Grey mould (botrytis on ornamentals)
Maintain excellent air circulation by spacing plants adequately and ventilating greenhouses. Remove dead flowers, leaves and plant debris immediately — these are the primary entry points for botrytis. Water in the morning and avoid wetting flowers and foliage. Avoid overcrowding container displays. In autumn and winter, reduce watering and provide gentle heat in greenhouses to prevent condensation and high humidity. Inspect stored bulbs and tubers regularly for signs of grey mould.
How to Treat Grey mould (botrytis on ornamentals)
Remove all infected plant parts immediately, placing them in a sealed bag rather than on the greenhouse floor where spores will spread. Improve ventilation and reduce humidity around remaining plants. Spray with a general fungicide if infection is widespread. For stored bulbs, dust with sulphur before storage and check monthly for signs of mould, discarding any affected specimens. Improve growing conditions to prevent recurrence — botrytis is an indicator of excessive humidity and poor air circulation.
Grey mould (botrytis on ornamentals) in Ireland
Grey mould is one of the most common plant diseases in Irish greenhouses and conservatories, driven by the cool, humid conditions that prevail for much of the year. The mild Irish autumn and winter, combined with reduced ventilation as gardeners close up greenhouses, creates ideal conditions for botrytis to thrive on ornamental plants. Irish gardeners overwintering geraniums, fuchsias, dahlias and begonias under glass must be particularly vigilant. The disease is also common on outdoor bedding plants during prolonged wet spells in summer. Good hygiene and ventilation are the most important preventive measures in Irish conditions.
Plants Affected by Grey mould (botrytis on ornamentals)
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