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Remarks (public):For a complete description including images see 
Remarks (internal):Distinguished from other species of Podosphaera in possessing a tuft of apical appendages which are very rarely branched at the apex. Damage is chiefly caused to nursery stock, reducing size and quality. Susceptibility to mildew in apple varieties is governed by one completely dominant gene (44, 1611), and is related to weather conditions (45, 3165). There is no evidence of matrodinous inheritance of resistance (45, 2529). Breeding of redstart varieties appears to be the most promising control measure. Some good sources of resistance for breeding varieties are known (45, 2529). Effective fungicides include microfine sulphur, wettable sulphur, lime sulphur and karathane (45, 374; Anderson,1956). Streptothricin-like antibiotics from a species of Streptomyces give successful control on potted apple rootstocks (42: 180).
Description type:Non-original description 
Description:Podosphaera leucotricha (Ellis & Everh.) Salm., Mem. Torrey bot. Club 9: 40, 1900.
= Sphaerotheca leucotricha Ellis & Everh., 1888.
= Sphacrotheca castagnei Lév. f. mali Sorauer, 1892.
= Sphacrotheca mali Burr., in Ellis & Everh., N. Amer. Pyren. 1892.
= Albugo leucotricha (Ellis & Everh.) Kuntze, 1892.
= Oidium farinosum Cooke, 1887.
= Oidium mespili Cooke, 1887.
Mycelium amphigenous, persistent thin effused. Conidia in long chains, ellipsoid often more or less globose, about 22-30 x 15-20 µm with distinct fibrosin bodies. Cleistothecia densely gregarious rarely scattered; globose or sometimes slightly pyriform, cells 10-16 µm wide. Appendages of 2 kinds: one set springing from the apex of the cleistotheciurn, the other inserted basally; apical appendages 3-11 usually 3-5, more or less widely spreading, 3-7 times as long as the diameter of the ascocarp, straight rigid thick walled 6-10 µm thick, dark brown towards the base, paler towards the tips, apex usually undivided or very rareb dichotomously branched 1-2 times; basal appendages rudimentary rarely well developed, short, more or less tortuous, pale brown, sisnple or irregularly branched. Ascus oblong to subglobose, 55-70 x 44-55 µm. Ascospores 8, ovate to elliptic, 22-26 x 12-15 µm.
Hosts: On Malus spp., chiefly on M. pumila (apple), peach (Prunus persica), quince (Cydonia ualgaris) and Photinia spp. also attacked (Hirata, 1966). Also reported on almond fruit (43, 2544). Disease: Powdery mildew of apple.
Geographical distribution: Africa (?Kenya, Rhodaia, South Africa, Tanzania); Asia (China, India, Israel, Japan, U.S.S.R.); Australia and New Zealand, Europe (widely distributed) North America (Canada and U.S.A.); South America (Argentina, Brazil, Chile, Colombia, Peru). (CMI map 118).
Physiological specialization: Not known.
Transmission: Ovcrwinters on host as dormant mycdium in blossom buds. The role of deistothecia in overwintering is
doubtful. Spread by wind-borne conidia (Anderson, 1956).
Literature: Blumer, Beitr. Krypt. Fl. Schweiz 7(1): 148-153, 1933; Blumer, Echte Mehltaupilze pp. 159-168, 1967 (taxonomy); Sprague, U.S. Dept. Agr. year Book, pp. 667-670, 1953; Anderson, Diseases of Fruit Crops, pp. 139- 143, 1956; Wartenberg, Phytopath. Z. 39:16-24, 1960 (disease); Mowry, Phytopathology 55:76-78, 1965 (inheritance of resistance); Zaracovids, Trans. Br. mycol. Soc. 48: 553-557, 1965 (germination); Hirata, Host range and geographical distribution of the powdery mildews, Japan: Niigata Univ., 1966.

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