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.
Small brown patches sometimes appear on the living leaves. As a rule these are few in number, and practically do no harm. Now and again, however, these patches are crowded on the leaves, which in consequence turn yellow, and fall quite early in the season. This, of course, materially affects the crop, not only for the present, but also for the following season. If the trees are not too large, spraying with Bordeaux mixture, when the disease is first observed, checks its spread.
The fungus perfects its fruit on the dead, fallen leaves during the winter, and it is only by means of the spores produced in these fruits that the young leaves can be infected the following season; hence it is advisable to have all such leaves removed when they fall. This may appear to be impracticable advice, yet it is just as well that the facts should be known, whether the advice is followed or not.