. Diseases of economic plants. Plant diseases. Pomaceous Fruits 47 '^Leaf-spots ^^"^'^ (various fungi) (see also black-rot, p. 42). — Aside from the leaf diseases of apple already mentioned, there are numerous other leaf-spots due to various causes. These spots partake of the same general character. That is, they are brown to tan-col- ored, at first circular, later irregularly circular, defi- nitely bordered, and usually concentrically marked. If abundant, or if they enlarge rapidly upon the leaves, they cause their premature fall, and largely defoliate the tree. Such spots pre- vail to g
. Diseases of economic plants. Plant diseases. Pomaceous Fruits 47 '^Leaf-spots ^^"^'^ (various fungi) (see also black-rot, p. 42). — Aside from the leaf diseases of apple already mentioned, there are numerous other leaf-spots due to various causes. These spots partake of the same general character. That is, they are brown to tan-col- ored, at first circular, later irregularly circular, defi- nitely bordered, and usually concentrically marked. If abundant, or if they enlarge rapidly upon the leaves, they cause their premature fall, and largely defoliate the tree. Such spots pre- vail to greater or less ex- tent in all apple orchards but are most destructive in the Southern states. Numerous species of fungi have been isolated from these spots; some of them undoubtedly sustain a causal relation to the dis- ease. Sheldon claims that in West Virginia much of the apple leaf-spot is due to an Illosporium. Whatever the actual causal fungi may be, these spots are all, or nearly all, of fungous origin and are amenable to preventive spraying. The first of three or four applications should be given with the opening of the leaf buds. Hypochnose "^' ^'' {Corticium stevensii (Noack) Burt). — Superficially this disease resembles the blight, with which it is hkely to be confounded by the casual observer. It may. Fig. 21, — Apple leaf-spot in late stage of development, showing concentric rings. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Stevens, Frank Lincoln, 1871-1934; Hall, John Galentine, 1870-. New York, Macmillan
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Keywords: ., bookauthorstevensf, bookcentury1900, bookdecade1920, bookyear1921
