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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Sooty bark disease was first observed on sycamore in Wanstead Park, London, in 1945 and the progress of this outbreak was described later (Gregory & Waller, 1951). The symptoms are progressively, foliar wilting and dieback followed by shedding of bark on the branches and main trunk. The latter is associated with the formation of thick brownish-black layers of dry conidia of the fungus under the bark with characteristic black masses. A greenish-yellow staining occurs in the wood of affected regions, extending up and down the stem from this centre and connected with sporing lesions where this is in contact with the bark. This discoloration fades on the death of the tree when the wood becomes uniformly pale grey. Cryptostroma corticale can be cultured from the stained areas. Despite the close association of C. corticale with the disease, its role as sole cause of the disease has only been fully demonstrated recently (R. Strouts, pers. comm.). The fungus is readily established in axenic culture (Czapek Dox Agar, PDA) from fresh conidia which germinate freely but does not form its characteristic stroma and conidia under these conditions. Townrow (1954) observed that the fungus was favoured by relatively high temperatures as its growth rate in culture at 25°C was 3 times that at 10°C. The disease declined after the outbreak of 1945 (35, 130) but reappeared in 1976. It is thought to be favoured by warm summer conditions. Cryptostroma corticale occurs as a saprophyte of woody substrates and was originally described from this source. It has been recorded from sawn sycamore timber (46, 1367, 3240) and sycamore wood pulp (48, 3165). Cases of severe allergic reactions to the conidia are reported in workers using timber infected with the sporulating fungus in Germany and USA (45, 267, 615). Control measures rely on early detection and strict sanitation.  
Description type:Non-original description 
Description:Cryptostroma corticale (Ellis & Everh.) Gregory & Waller, Transactions of the British Mycological Society 34: 594, 1951.
Coniosporium corticale Ellis & Everh., 1889.
Mycelium immersed, septate, dark brown, anastomosing. Colonies effuse, dark blackish-brown, powdery, confluent. Stromata extensive, situated beneath the bark, multilocular, consisting of a fertile basal region of large-celled, angular, dark brown pseudoparenchyma which is connected by vertical columns of thin-walled elongated cells surrounded by sclerotioid cells to an upper infertile region consisting of sclerotioid inflated cells with an outer layer of radially elongated thin-walled cells. Conidiophores macronematous, often parallel, smooth, branched mainly at the base, brown, becoming hyaline and tapered towards the apex, up to 26 µm long, 4-6,5 µm wide at the base, 2-3 µm wide at the apex, often mixed with hyaline paraphyses. Conidiogenous cells holoblastic, annellidic, integrated, rarely discrete, terminal, indeterminate, with up to 4 closely percurrent proliferations. Conidia 5-12 x 3,5-4 µm, non-septate, smooth, pale brown, comparatively thick-walled, often with a single, small guttule, apex obtuse, base truncate to obtuse, globose, cylindrical or obovoid, often formed in unbranched chains and adhering after secession.
Hosts: Acer campestris, A. platanoides, A. pseudoplatanus, A. saccharum and other species; Tilia spp., Carya alba and on dead wood, sawn timber and pulp of sycamore.
Disease: Sooty bark disease of sycamore.
Geographical distribution: Europe (UK, France, Germany, Italy); North America (USA, Canada) (CMI Map 272, ed. 2, 1971).
Physiologic specialization: None known.
Transmission: By air-borne conidia.
Literature: Gregory & Waller, Transactions of the British Mycological Society 34: 579, 1951; Townrow, Forestry Commission, Report on Forest Research for the Year Ending March 1953: 118-120.

 
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