The effect of condensation on sporulation ofHelminthosporium solani on potato tubers infected with silver scurf and held in simulated store conditions

1997 ◽  
Vol 40 (2) ◽  
pp. 169-180 ◽  
Author(s):  
Claire E. Hardy ◽  
P. J. Burgess ◽  
R. T. Pringle
Keyword(s):  

2004 ◽  
Vol 22 (4) ◽  
pp. 690-695 ◽  
Author(s):  
Marcos G. Cunha ◽  
David M. Rizzo

A new potato tuber disease has been observed in the Tulelake region, California, USA, since 1995, with tuber symptoms suggestive of silver scurf disease (Helminthosporium solani). In this work we isolated, identified and demonstrated the nature of the causal agent of this potato disease in California. In addition, the distribution of H. solani in potato fields and the inoculum potential at harvest time were investigated. Disease progress and H. solani spore populations were also characterised under commercial storage conditions. The main fungal genera associated with potato tubers in storage were Helminthosporium solani, Colletotrichum sp., Fusarium sp., and Rhizoctonia sp. The results of Koch's postulates indicated that H. solani is responsible for the outbreak of silver scurf in the Tulelake region. In a disease survey in three commercial potato fields naturally infested, H. solani infections occurred in all fields. However, the extension of the infections differed significantly between the fields. During potato storage, silver scurf usually increased over time. The percentage of the tuber surface covered by silver scurf varied from 3.5% up to 35.5% during the storage period. The number of H. solani lesions per tuber also progressively increased from 6% up to 35%, six months after storage. H. solani spore populations also increased over time in all studied potato stores; nevertheless, they followed no consistent pattern, exhibiting multiple and variable peaks of increase and reduction during the period of storage.



2015 ◽  
Vol 4 (1) ◽  
pp. 84
Author(s):  
McMoran D. W. ◽  
Buller S. J.

Silver scurf is an economically important disease on potato tubers caused by Helminthosporium solani. Two studies were established near Mount Vernon, WA at Washington State University NWREC on 20 May 2011 and 21 May 2012 in Skagit silt loam soil.  Five treatments included: penthiopyrad applied at 45 days after planting (dap), penthiopyrad applied at 60 dap, azoxystrobin (Quadris; 9 oz/acre) applied at 45 dap, and azoxystrobin applied at 60 dap, and a non-treated non-irrigated control.  This study did not control for the effect of irrigation, as azoxystrobin- and penthiopyrad-treated plots were drip-irrigated while non-treated plots were not irrigated. The results of this study are therefore limited but do suggest a reduction in silver scurf incidence and severity with no significant impact on yield of potatoes when treated fungicide applied through drip irrigation systems.





Plant Disease ◽  
1998 ◽  
Vol 82 (2) ◽  
pp. 213-217 ◽  
Author(s):  
Claudia Olivier ◽  
Donald E. Halseth ◽  
Eduardo S. G. Mizubuti ◽  
Rosemary Loria

Seven organic and inorganic salts were tested for suppression of silver scurf, a postharvest disease of potato tubers caused by Helminthosporium solani. Potassium sorbate, calcium propionate, sodium carbonate, sodium bicarbonate, potassium carbonate, potassium bicarbonate, and ammonium bicarbonate were added to V8 agar at concentrations of 0.06–0.2 M. Radial growth of H. solani was significantly reduced (P < 0.05) by all salts at all concentrations. All salts except sodium bicarbonate and potassium bicarbonate were fungicidal at 0.2 M. Effects of postharvest salt treatments on disease severity and sporulation of H. solani on inoculated and naturally infected potato tubers were evaluated in separate experiments. Greenhouse-grown tubers were inoculated with H. solani spore suspensions (2 × 105 spores/ml), incubated for 5 days, dipped into 0.2 M solutions of each of the salts, and incubated in a moist chamber at 22–24°C for 6 weeks. All salt treatments prevented lesion development and sporulation of H. solani and differed significantly (P < 0.05) from the control. Postharvest applications of test compounds (0.2M) also significantly (P < 0.05) reduced disease severity and H. solani sporulation on naturally infected, field-grown tubers after 15 weeks of storage at 10°C. Salt treatments did not differ in disease or pathogen suppression. These relatively nontoxic organic and inorganic salts have potential as postharvest applications for control of silver scurf.



1973 ◽  
Vol 16 (2) ◽  
pp. 109-125 ◽  
Author(s):  
D. C. Graham ◽  
G. A. Hamilton ◽  
C. E. Quinn ◽  
A. D. Ruthven
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.



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.



Plant Disease ◽  
1999 ◽  
Vol 83 (9) ◽  
pp. 814-818 ◽  
Author(s):  
Claudia Olivier ◽  
Carol R. MacNeil ◽  
Rosemary Loria

Silver scurf, caused by Helminthosporium solani, is an economically important postharvest disease of potato tubers. Organic and inorganic salts were evaluated for their ability to suppress silver scurf lesion development and sporulation of H. solani on potato tubers. Tubers were treated immediately after harvest with 0.2-M solutions of potassium sorbate, calcium propionate, sodium bicarbonate, sodium carbonate, ammonium bicarbonate, or water. Tween 20 was added as a surfactant to most treatments. Potassium sorbate (0.1 M), acidified potassium sorbate and calcium propionate treatments (0.2 M), and calcium chloride treatments (0.136 M) were included in additional experiments. Tubers were stored under commercial storage conditions for 4 to 6 months prior to disease evaluation. The extent of disease suppression varied among experiments; however, some treatments consistently reduced disease. Lesion formation on the tuber surface was reduced by 26 to 60% using potassium sorbate (in three of four experiments) compared to water-treated or untreated tubers. Sporulation was suppressed by 0.2 M potassium sorbate (78 to 99% reduction) in all four experiments. Sodium carbonate reduced lesion formation in two experiments and sporulation in three of four experiments. Other treatments inconsistently suppressed lesion formation or sporulation, or did not reduce disease. Addition of Tween or acidification of organic salt solutions did not improve silver scurf suppression in most cases. Potassium sorbate has very low mammalian toxicity and great potential as an innocuous and inexpensive postharvest fungicide for suppression of silver scurf during potato storage.





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