Diseases of economic plants (1910) Diseases of economic plants diseasesofeconom02stev Year: 1910 88 DISEASES OF ECONOMIC PLANTS fungi have been isolated from these spots,1 some of them may sustain a causal relation to the disease. Whatever the actual causal fungus may be, these spots are all, or nearly all, of fungous ori- gin and are amenable to preventive spraying with Bordeaux mixture. The first of three or four applications should be given with the opening of the leaf buds. Illosporiose, leaf spot (Illosporium malifolio- rum Shel.). — This is said by Sheldon2 to be the cause of much of t
Diseases of economic plants (1910) Diseases of economic plants diseasesofeconom02stev Year: 1910 88 DISEASES OF ECONOMIC PLANTS fungi have been isolated from these spots,1 some of them may sustain a causal relation to the disease. Whatever the actual causal fungus may be, these spots are all, or nearly all, of fungous ori- gin and are amenable to preventive spraying with Bordeaux mixture. The first of three or four applications should be given with the opening of the leaf buds. Illosporiose, leaf spot (Illosporium malifolio- rum Shel.). — This is said by Sheldon2 to be the cause of much of the defoliation of apple or- chards in West Virginia and adjacent states. The spots are circular, 5-15 mm. in diameter, brown or mottled and gray, con- centrically marked. For treatment see page 100. 1 Notably by Hartly, Minnesota, and by Lewis, I. M., New Hampshire Agr. Exp. Sta. Rpt. 19-20, November, 1908. 2 Sheldon, J. L., Torreya, 8, 141, June, 1908. Fig. 33.—Apple leaf spot in late stage of development, showing concentric rings. Original.
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