Grey Mould (Botrytis cinerea)

Plants/trees affected :

Can affect most plants and stored fruit.

Symptoms

Early symptoms are brown ‘dead’ patches on leaves, stems and buds, white/brown areas on fruit and petals, followed by the appearance of a grey ‘felt-like’ fuzzy mould. Fruit can also fail to develop or dry up and infected buds may droop with stems developing grey/black areas.  As the infection matures black sclerotia (hardened mass of dormant fungi, about 2-5mm in size) are produced, these fall to the ground and the disease will over winter in this format until favourable conditions restart the cycle.

Causes

Grey mould is a fungus whose spores are almost always in the air all around us, living on both healthy and dead plant material.  The fungus thrives in cool wet conditions where humidity is high and temperatures are low.  It is spread by wind, rain, overhead watering and pesticide spraying, attacking plants that have been stressed or received an injury of some sort.  Once a plant is affected it can spread to all parts depending on its species and variety.

Prevention

Regularly check all plants for signs of infection and pay particular attention to air circulation in the garden and greenhouse.  Plants and shrubs need to be kept in a well ventilated situation with low humidity and not planted too closely together. Remove all dead and injured plant material before it can become affected, dead head regularly and tidy away leaf litter and plant debris at the end of the season. Try also to avoid touching the grey mould as a cloud of spores could be released which will lead to further infections.

Treatment

• Remove and destroy all infected plant material back to healthy growth (do not compost).
• Apply an appropriate fungicidal spray, one which contains either myclobutanil or Penconazole. (N.B. always follow the manufacturers instructions).
• Armillatox or Jeyes Fluid can be used on bare soil or in greenhouses  during the winter to sterilise the areas and destroy the over wintering sclerotia.