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Botrytis cinerea The Grey Mould
Botrytis cinerea is a very common plant parasitic fungus and you have possibly seen it a number of times in your back garden. It is a weak parasite and usually confines its attention to delicate, ripe or senescent plant tissues. So, it is found on dying flowers or ripefruits especially during prolonged wet weather or in shaded spots. As you can see in the photo, the mature and over-ripe strawberries on the right have been overrun by the fungus. The blue-grey mass over the surface of infected strawberries is made up of the dry, powdery spore masses of the fungus. This is one of my favourite shots. It shows the development, maturity and death of a strawberry fruit. The red strawberry at the centre of the field of view is in contact with the infected berry and will be rapidly attacked. If it is picked at this time for market then it will deteriorate rapidly in the box and become soft and mushy as the hyphae of the fungus permeate the fruit and the enzymes break down the interior flesh. Spores of the fungus are dispersed by wind and rain and can cause damage to the flowers of a number of ornamental plants in the garden when conditions are right.
To find your own Botrytis rot, take some over ripe and mushy strawberries from the box during the season, put them in a plastic bag and leave them in a corner. In a few days you'll have a rich growth of Botrytis (and maybe some other moulds) running over the fruits. Important point is that the Botrytis strain from supermarket strawberries came from the source of the strawberries U.S.A? Central America? You can see how easily plant pathogenic fungi can be transported from place to place and how difficult it is to prevent introduction of serious plant pathogens into 'new' regions.
Botrytis is a weak parasite. This means that it can only attack fully mature or senescent tissues (flowers) or storage structures (bulbs etc.) that have been improperly stored or handled. See the effect it has on Geranium blossoms during wet weather Grey Mould (Botrytis) on Geraniums.