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 disease is very prevalent on the leaves of both Gooseberries and Currants, but is generally neglected, as its significance is mostly unknown to growers, or it is mistaken for the work of " green fly ". Leaves that are attacked - and as a rule every leaf on a bush is attacked when the fungus once gains a foothold - fall early in the season during a severe attack. This not only checks the full development of the fruit already present, but also unfavourably affects the crop of the following season, on account of the imperfectly matured wood. This disease is confined to the leaves, and its presence is indicated by the appearance of numerous very small warts, most abundant on the upper surface of the leaf, which commences to turn yellow soon after being attacked. If allowed to run its course the fungus spreads rapidly, the spores from the leaves first diseased being spread by wind, rain, insects, etc, to adjoining healthy leaves. If the bushes are sprayed with half-strength Bordeaux mixture, or with potassium sulphide, when the disease first appears, its spread will be arrested. This is certainly worth doing, as the disease saps the vigour of the bushes to a serious extent.
It is important to remember that when the leaves have fallen the bush is perfectly free from disease, and will remain so unless infected afresh. Such infection proceeds from the old fallen leaves the following spring; hence if the leaves are dug in during the winter, or got rid of in some way, the disease will not reappear.