Relationships between disease levels on seed tubers, on crops during growth and in stored potatoes. 3. Silver scurf

1980 ◽  
Vol 23 (2) ◽  
pp. 229-240 ◽  
Author(s):  
G. A. Hide ◽  
M. J. Adams
Keyword(s):  
2005 ◽  
Vol 82 (2) ◽  
pp. 41-48 ◽  
Author(s):  
V. Hervieux ◽  
R. Chabot ◽  
J. Arul ◽  
R.J. Tweddell

Silver scurf of potatoes (Solanum tuberosum), caused by the fungus Helminthosporium solani, is an important surface-blemishing disease of potato tubers. The objective of the study was to evaluate the efficacy of different fungicides applied to potato seed tubers for control of silver scurf. Field trials were conducted in Québec province in 1998 and 1999. Potato seed tubers infected with H. solani were treated with either talc, fludioxonil, mancozeb, iprodione, thiabendazole, imazalil or azoxystrobin, and planted at three locations in 1998 and two locations in 1999. The results showed that, under our experimental conditions, the fungicides tested, applied as seed treatments, did not significantly influence total and marketable yields as well as silver scurf severity on daughter tubers at harvest and after different storage periods. In addition, this study showed the influence of the experimental locations on silver scurf development and suggests that soil inoculum plays a role in the epidemiology of the disease.


1995 ◽  
Vol 124 (2) ◽  
pp. 219-234 ◽  
Author(s):  
D. M. Firman ◽  
E. J. Allen

SUMMARYThe transmission of silver scurf (Helminthosporium solani) disease of potatoes was examined in field experiments at Cambridge University Farm in 1988–90. Treatment factors examined were seed size, seed age, seed incubation, soil moisture regime and planting date. A laboratory experiment investigated the viability of conidia of Helminthosporium in soil stored under different conditions.Incubation of seed at high humidity before planting increased sporulation of Helminthosporium on seed tubers after planting and fewer conidia were produced from small seed than from larger seed. Delay in planting caused more rapid growth of Helminthosporium on seed tubers after planting.Early planting and late harvesting increased the severity of silver scurf on progeny tubers. Severity of silver scurf was also increased by ageing seed and by incubating seed. Weight loss of potato tubers during storage tended to be greater from treatments with most severe silver scurf in all years but a significant linear regression of weight loss on silver scurf severity was found in only one year out of three from a late harvest. The viability of conidia added to soil was found to decrease rapidly so that by 10 weeks after addition, < 1% of conidia were apparently viable.


Author(s):  
M. B. Ellis

Abstract A description is provided for Helminthosporium solani. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. 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. TRANSMISSION: Through infected seed tubers.


1967 ◽  
Vol 47 (6) ◽  
pp. 695-702 ◽  
Author(s):  
Jacquelin Santerre

The disinfection of potato seed tubers with formalin, organic and inorganic mercury compounds is useless against silver scurf of potatoes caused by Helminthosporium atrovirens. Although generally good surface disinfectants, these fungicides cannot reach the mycelium of the fungus growing underneath the skin. When conditions are again favorable, the pathogen will grow conidiophores that will bear conidia, the germination of which is not impaired by the previous treatments.Cultural practices such as fallow, crop rotation as well as soil treatments with Lanstan (soil fungicide) or Vapam (soil fumigant) did not reduce the percentage of infected tubers at harvest when used in conjunction with apparently disease-free potato seed tubers.Besides showing the ineffectiveness of disinfecting potato seed tubers, these results indicate that evaluating the true health condition of seed-potatoes according to whether or not the fungus is present on the skin is not to be relied upon, that sorting out visibly infected tubers does not suffice to free a "seed" from the disease, and that cultural practices and chemical soil treatments are useless if the seed-potatoes are already infected, thereby laying emphasis on the infected potato seed tubers as the main source of inoculum for silver scurf.


1993 ◽  
Vol 89 (2) ◽  
pp. 262-270 ◽  
Author(s):  
G. N. Mohan Kumar ◽  
N. Richard Knowles

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