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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Golovin (37: 400) has divided Leveillula into six sections on the basis of shape and size of the conidia. Distinguished from other powdery mildews by its endoparasitic habit, the mycelium not remaining limited to the epidermal layer but penetrating and ramifying in the mesophyll, the path of infection being through the stomata and not the cuticle. Conidia of L. taurica can germinate under a wide range of humidity (0-100%), although best at 85-100% RH. Conidia submerged in water germinate poorly (37: 521). Control is achieved by spraying or dusting infected plants with commercial preparations of lime-sulphur, water dispersible sulphur, sulphur dust, thiram and cuprous oxide. Early sowing combined with lime-sulphur treatments at low concentrations (1 in 120) greatly increased yields of broad beans (36: 566).
 
Description type:Non-original description 
Description:Leveillula taurica (Lév.) Arn., Annls Epiphyt. 7: 92, 1919.
= Erysiphe taurica Lév., 1851.
= Erysiphe taurica Lév. var. andina Speg., 1902.
= Erysiphe taurica Lév. var. zypophylli Maire, 1905.
= Oidiopsis taurica (Lév.) Salmon, 1906.
= Ovularia indica Rao, 1968.
Mycelium permeating the host tissue, amphigenous, often covering the whole plant, persistent, effused, densely compacted, tomentose, membranaceous or crustaceous, usually white, often pale buff in places, sometimes completely evanescent. Cleistothecia generally scattered, rarely gregarious, often somewhat embedded in a dense superficial mycelium, 135-250 µm diam., globose or becoming concave at maturity; peridium of polygonal cells, up to 10 µm diam. Appendages numerous, hypha-like, simple, densely interwoven, short, indistinctly branched, colourless to olivaceous brown. Asci usually about 20 but sometimes less or up to 35 in each ascocarp, 2-spored, ovate, distinctly stipitate, 70-110 x 25-40 µm. Ascospores large, cylindrical to pyriform, sometimes slightly curved, variable in size, 25-40 x 12-22 µm. Conidia (form-genus Oidiopsis Scalia sect. Longispora; Blumer, 1967) borne singly on short hyphal branches, large, predominantly of two distinct shapes, cylindrical and navicular, varying in size on different hosts, (25-) 50-79 (-95) µm long, 14-20 µm wide.
Hosts: On Gossypium barbadense, G. hirsutum and Cyamopsis psoraloides. Also on many other trees and shrubs belonging to the Leguminoseae, Malvaceae and Euphorbiaceae (Salmon, 1900; Blumer, 1933; Tarr, 1955; 37: 521).
Diseases: Powdery mildew of cotton and guar. The host becomes completely covered with the fungus which mostly forms conidia and rarely cleistothecia. Severe attacks cause defoliation. Komarov (1895) reported that in Seravschan-Turkestan every plant of the steppes up to 1219-1524 m. is attacked. The fungus does not occur beyond 1829 m.
Geographical distribution: World wide but mainly in the mediterranean region, Central Europe and the Near East (Dennis, 1960; CMI Map 217; 37: 400).
Physiological specialization: Zwirn (1943) and Kamat & Patel (1948) reported L. taurica to be highly specialized, but Nour found contradictory evidence (37: 521) indicating that this species is much less specialized than other powdery mildews, a single strain being able to infect a wide range of host genera.
Transmission: Wind borne. In the Sudan the pathogen over-summers on Euphorbia heterophylla, a common weed (37: 521).
Literature: Blumer, Echte Mehltaupilze, pp. 324-333, 1967 (taxonomy & general); Salmon, Mem. Torrey bot. Club 9: 215-221, 1900 (taxonomy & general); Tarr, The fungi and plant diseases of the Sudan, pp. 23-24, 1955; Komarov, Scripta Botanica 4: 269-278, 1895; Dennis, British Cup Fungi, pp. 221-222, 1960; Zwirn, Palest. J. Bot. Jerusalem 3: 52-53, 1943; Kamat & Patel, Indian Phytopath. 1: 153-158, 1948; Rao, Mycopath. Mycol. appl. 34: 47-48, 1968.
 
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