This section is from the book "Commercial Gardening Vol3", by John Weathers (the Editor). Also available from Amazon: Commercial Gardening, A Practical & Scientific Treatise For Market Gardeners.
This is a very destructive and widely diffused disease, but with prompt attention can readily be detected and checked in its career. Gooseberries are most frequently attacked, although Black- and Red-currant bushes sometimes show the disease. The most usual symptom of the presence of this parasite is the sudden wilting of the foliage of a branch, or sometimes of the entire bush. This may occur soon after the leaf buds have expanded, or later in the season when the bush is in full leaf.
The conidial form of the fungus, called Botrytis, is responsible for the mischief done, the higher or Sclerotinia stage being rarely, if ever, produced, at least in this country. The fungus is a wound parasite, and enters the stem at the collar through some small wound. When once in the tissues the mycelium spreads in the bark and wood. If it completely girdles the stem the whole bush dies; but more frequently it attacks one main branch at its base, and when the mycelium of the fungus has increased to such an extent as to cut off the supply of water taken up by the root, wilting, followed by the death of the part affected, is the result. Soon after the wilting of the leaves, tufts of a grey or mouse - coloured mould burst through the bark at the base of the diseased branch, which, if not soon removed, will gradually become covered with the mould or Botrytis form of the fungus. If the diseased branch is promptly removed the remainder of the bush may continue to flourish, although so far as my own experience is concerned this is not the case; the mycelium from the diseased branch having spread into adjoining parts, and year by year additional branches die. Taking everything into consideration, I think the most economical course is to remove and burn the bush when once it is clearly established that it is infected. Diseased bushes should be burned at once, for in addition to the great number of Botrytis spores that would continue to be produced on the dead wood, numerous small black bodies termed sclerotia develop on the dead bark. These eventually fall away and give origin to Botrytis spores.
Young shoots are also often attacked, and die back for some distance, hence the popular name of "Die-back " amongst market gardeners. It is well to remove and burn all such as soon as observed, to prevent further infection.
Finally, the leaves and also the fruit are sometimes injured by the same fungus, which often follows Red Spider or green fly. The leaves that are attacked often bleach, and have a silvery look round the edge. The berries show a brownish stain, which finally becomes soft and covered with the mould.
Prunings should not be left under the bushes, neither should they be left in heaps here and there to rot. All such accumulations form centres of disease, from which the fungus spores are diffused in myriads by wind, birds, etc.
Where the disease has previously existed, the bushes, and also the ground, should be thoroughly drenched with a solution of sulphate of copper during the winter months, before the leaf buds expand. This should be followed by a spraying with half-strength Bordeaux mixture just when the fruit is set.