Sweet pepper 'Redskin'

We have a problem with our pepper plant in that there is mould both black on the leaves, and a beige fur on the stalks. Although it is still producing fruit, the fruit is now getting small black spots on them. What can be done to eradicate this? It is on the west aspect of the garden and is under a plastic 'home made' cover with stakes to keep it away from the plant. Can the plant be trimmed to remove the bad parts to prevent the whole plant being infected?

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