Diseases of economic plants (1921) Diseases of economic plants diseasesofeconom01stev Year: 1921 Ornamental Plants 431 the leaf dies. They also become more regular in outline than in their earlier stages. Portions of the leaflets outside of the area actually spotted often turn yellow, and the diseased leaflets fall off prematurely. Thus the beds beneath diseased plants are often strewn with fallen leaves. All infective material should be gathered and burned, and by use of a good dormant spray both bushes and ground be Fig. 220. — Rose mildew; diseased and healthy shoots. well cleared of s
Diseases of economic plants (1921) Diseases of economic plants diseasesofeconom01stev Year: 1921 Ornamental Plants 431 the leaf dies. They also become more regular in outline than in their earlier stages. Portions of the leaflets outside of the area actually spotted often turn yellow, and the diseased leaflets fall off prematurely. Thus the beds beneath diseased plants are often strewn with fallen leaves. All infective material should be gathered and burned, and by use of a good dormant spray both bushes and ground be Fig. 220. — Rose mildew; diseased and healthy shoots. well cleared of superficial spores. Ammoniacal copper car- bonate used once each week is effective after the plants are in foliage. Lime-sulfur or Bordeaux mixture may be used when the residue on the foliage is not objectionable. Powdery-mildew {Sphcerotheca pannosa (Wallr.) Lev. or S. humili (DC.) Burr, Oidium). — This is perhaps the most wide-spread and destructive of all rose diseases both under glass and in the open, being especially destructive to the
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