Diseases of flowers and other Diseases of flowers and other ornamentals diseasesofflower118smit Year: 1940 Diseases of Flowers and Other Ornamentals 65 Oak-Root-Fungus Disease, Armillaria Root Rot.—Rose bushes some- times die from the attacks of this well-known disease, especially if they stand near an affected tree of any kind. The characteristic white fungus felt of Armillaria mellea is found between the bark and wood, and brown or black, shoestring-like rhizomorphs on the surface of the roots. Rose bushes affected with oak root fungus should be dug out, and the hole made large enough to r
Diseases of flowers and other Diseases of flowers and other ornamentals diseasesofflower118smit Year: 1940 Diseases of Flowers and Other Ornamentals 65 Oak-Root-Fungus Disease, Armillaria Root Rot.—Rose bushes some- times die from the attacks of this well-known disease, especially if they stand near an affected tree of any kind. The characteristic white fungus felt of Armillaria mellea is found between the bark and wood, and brown or black, shoestring-like rhizomorphs on the surface of the roots. Rose bushes affected with oak root fungus should be dug out, and the hole made large enough to remove all roots. In replanting, fresh soil should be used. By this means replants may live for several years even though the disease eventually reappears. See page 84. Fig. 28.—Rose mildew. Powdery Mildew.—The young leaves, buds, shoots, and canes of roses often become covered with a white, frosty, or sometimes dense, felty, growth of the fungus Sphaerotheca pannosa (fig. 28). This distorts, stunts, and sometimes kills affected parts. Some varieties are much more susceptible than others. For control see the last section under this flower. Root-Knot Nematode.—The characteristic symptom of this pest is the small, roundish galls or swellings abundantly developed all over the roots, especially on hothouse roses. This causes stunting of the plants. The parasite is the well-known garden nematode, or eelworm, Hetero- dera marioni, which attacks the roots of many other kinds of plants. (See p. 82.) Affected plants should be destroyed. Greenhouse soil that is infested with this pest must be discarded or steam-sterilized (p. 80). This also applies to benches, cold frames, tools, and other equipment which may
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