This is a disease of stone-fruits in general. On the apricot it is especially prevalent in California. Reddish brown, dusty pustules are produced on the lower surfaces of the leaves (Fig. 43). This occurs late in the summer. The causal fungus, Puccinia Pruni - spinosoe, may induce premature defoliation in cases of severe infection. (See full discussion under Plum, page 377. See also Cherry, page 187, and Peach, page 319.)
Fig. 43. - Apricot rust.
In California this disease has been troublesome for many years. Since 1880 it has been the subject of inquiry and writing, with reference particularly to its cause and control. In recent years the question of Crown Gall on a great variety of plants has been illuminated, and the more important phases of the disease have been carefully studied. (For a fuller discussion of the disease, see under Apple, page 108.)