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Remarks (public):For a complete description including images see www.cababstractsplus.org/dfb 
Remarks (internal):Burke (1938) gave a full account of silver scurf in U.S.A. where it has been known to cause considerable losses of stored potatoes to growers of certified seed. The disease may be hardly noticeable at the time of harvest but increases rapidly in storage, it is somewhat more severe on tubers from peat soils than on those from podsols. Incidence may be aggravated by excessive nitrogen fertilization. Optimum conditions for development are high R.H. at 20-24°C; control is obtained by dry storage and to a lesser degree by disinfection of seed potatoes and soil treatment with quintozene. Tubers should be left to dry in the field for 3-4 hr after digging or dried indoors for 5-7 days. With the increase in quantity of potatoes washed and packed in polythene bags, disfiguring effects of silver scurf have become much more apparent. Trials by Busch (1958) in Canada with 21 chemicals showed that only puraseed, semesan bel, karathane, terraclor and manzate prevented sporulation with a minimum of damage to eyes. Kramer (1942) pointed out that in Brazil not only might the fungus itself be responsible for heavy losses, but it paved the way for infection of tubers by secondary parasites. Bintje is said to be a very susceptible variety of potato, Bona and Majestic fairly resistant and Krasava highly so.
 
Description type:Non-original description 
Description:Helminthosporium solani Dur. & Mont., Flore d'Algerie, Cryptogamie p. 356, 1849.
= Brachysporium solani (Dur. & Mont.) Sacc., Syll. Fung. 4: 428, 1886.
= Demarium atrovirens Harz, Bull. Soc. Nat. Moscow 44: 129, 1871.
= Spondylocladium atrovirens (Harz) Harz ex Sacc., Syll. Fung. 4: 483, 1886.
= Helminthosporium atrovirens (Harz) Mason & S. Hughes, in Hughes, Can. J. Bot. 31: 631, 1953.
= Cladosporium abietinum Zukal, Verh. Zool.-bot. Ges. Wien 37: 44, 1887.
Colonies dark brown to black, effused, hairy. Mycelium immersed, hyphae sub-hyaline to brown, smooth, sometimes verrucose in culture, 1-5 µm wide, occasionally swollen up to 8 µm wide at the point of origin of the conidiophores. Stromata rudimentary and composed of only a few thick-walled cells or absent. Conidiophores arising singly or in groups, sometimes from the cells of a small stroma but more often terminally and laterally on the hyphae, erect, simple, straight or flexuous, brown to very dark brown, paler near the apex, usually smooth, septate, with small pores at the apex and laterally beneath the upper 1-8 septa, 120-600 µm long, 9-15 µm wide near the base, 6-9 µm wide at the apex. Conidia arising through pores at the apex of the conidiophore and in verticils beneath the upper septa, straight or curved, obclavate, smooth, subhyaline to brown, 2-8-pseudoseptate, 24-85 (av. 39) µm long, 7-11 (av. 9,4) µm wide in the broadest part, tapering to 2-5 µm wide at the apex, with a well-defined dark brown to black scar at the base.
Hosts: Solanum tuberosum.
Disease: Silver scurf of potato tubers. It causes a blemish of the skin which becomes discoloured brown or silvery in patches, more conspicuous in spring especially on greened tubers. The silvery appearance is most apparent when tubers are washed. Sometimes the affected areas become dry and flake-off. Where infection is severe under storage conditions the entire surface of the tuber may become sooty owing to the presence of large numbers of conidiophores and conidia.
Geographical distribution: CMI Map 233 shows distribution up to 1951. Countries from which the disease has
been reported since then include: Greece, India, Jersey, Mozambique, Peru, Switzerland, U.S.S.R., Venezuela. Physiological specialization: Not known.
Transmission: Through infected seed tubers.
Literature: Burke, Bull. Cornell agric. Exp. Stn. 692, 1938; Busch, Pl. Dis. Reptr 42: 441-443, 1958; Kramer, Biológico 8: 83-86, 1942; Ellis, Mycol. Pap. 82: 3-5, 1961; Anon., Advis. Leafl. Minist. Agric. Fish. 279, 1963.

 
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