These are one of the most common type of plant diseases.
Also called "grey mould", they are serious, widespread diseases worldwide on flowers, vegetables, ornamentals, fruits and some field crops.
They are very common in greenhouses.
Mainly occurs on flowers or fruit, but can also appear as damping off of seedlings, stem cankers, spots on leaves, or rots of below ground parts such as tubers or bulbs.
Blossom blights often precede rots on other parts of the plant.
Flowers turn brown and rots, and the infection spreads to other plant parts.
In humid conditions a noticeable fluffy grey/brown growth is produced that is characteristic of Botrytis disease.
Plants Affected: Vegetables, fruits, ornamentals and some field crops.
Natural - In greenhouses humidity should be reduced by improved ventilation and increased heating. Harvested plant storage organs such, as onion bulbs can be stored at 32-50 degrees C for 2-4 days to remove excess moisture then stored at low temperatures in as dry conditions as possible.
Chemical - Benlate, Fongarid (soil drenches), Zineb, Difolitan and Maneb have been used to control Botrytis. Strains of Botrytis resistant to some of these chemicals have been found.
Fire Botrytis (Botrytis tulipae)
Brown spots on tulip flowers & leaves. Spots may spread to cause rot of the stem. Infected bulbs are stunted and pale in growth. Grey fur-like damage may develop on damaged parts in warm humid weather. This fungus develops sclerotia (seed-like structures) which can remain in the soil or stay attached to infected plants. Hygiene is therefore important.
Control: Mancozeb or benomyl. Discard infected bulbs, practice crop rotation, avoid overhead irrigation, and do not apply excessive amounts of nitrogenous fertilizers.
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