Occurrence, development, and losses associated with silver scurf and black dot on Colorado potatoes

Hunger, R. M.; McIntyre, G. A.

doi:10.1007/bf02855598

Cited by 32 publications

(30 citation statements)

References 12 publications

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“…coccodes frequently infects potato stems and other tissues early in the growing season but symptoms which include foliar chlorosis and necrosis, and signs of the pathogen in the form of sclerotia are often not expressed until relatively late in the growing season (Andrivon et al 1998;Johnson and Miliczky 1993;Pasche et al 2010). Potato yield and tuber quality can be reduced by C. coccodes (Hunger and McIntyre 1979;Johnson 1994;Mohan et al 1992;Pasche et al 2010;Stevenson et al 1976;Tsror et al 1999); however, the effect on yield is variable and yield losses are not always evident (Kotcon et al 1985;Read and Hide 1995;Pasche et al 2010;Scholte et al 1985). Even though yield losses are not always observed, C. coccodes is a serious threat to potato production (Pasche et al 2010).…”

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confidence: 98%

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Response of Colletotrichum Coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation

2011

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A plant inoculation assay was developed and used to evaluate fungicide efficacy and application timing for reduction of infection of potato stems by Colletotrichum coccodes. Incidence of infected stems treated with azoxystrobin, pyraclostrobin, fluoxastrobin, and mandipropamid + difenoconazole was significantly less than the non-treated control plants when fungicides were applied prior to inoculation. However, fungicide application after inoculation did not significantly reduce infection. Chlorothalonil and mancozeb were not effective in preventing infection by C. coccodes. Additionally, early season fungicide applications by center pivot chemigation in commercial potato fields were evaluated as a potential black dot management tactic. Below-ground stems sampled from replicated plots in commercial fields where azoxystrobin was applied by chemigation at 50 and 67 days after planting (DAP) had significantly less stem surface area covered with sclerotia at 79 DAP than the non-treated control in two of 2 years. However, the effect was not observed both years at a subsequent collection at 102 DAP and only one of 2 years at 140 DAP. Latent infections were detected in non-symptomatic plants collected from the field.Resumen Se desarrolló y utilizó un ensayo de inoculación de plantas para evaluar la eficacia y tiempo de aplicación de fungicida para la reducción de la infección en tallos de papa por Colletotrichum coccodes. La incidencia de tallos infectados tratados con azoxystrobin, pyraclostrobin, fluoxastrobin y mandipropamid + difenoconazole, fue significativamente menor que las plantas testigo no tratadas cuando se aplicaron los fungicidas antes de la inoculación. No obstante, la aplicación del fungicida después de la inoculación no redujo significativamente la infección. Clorotalonil y mancozeb no fueron efectivos en prevenir la infección por C. coccodes. Adicionalmente, se evaluaron aplicaciones de fungicidas al principio del ciclo de cultivo por quimirrigación de pivote central en campos comerciales de papa, como táctica potencial de manejo de la mancha negra. Los tallos subterráneos muestreados de lotes con repeticiones en campos comerciales donde se aplicó azoxistrobin por quimirrigación a 50 y 67 días después de la siembra (DAP), tuvieron significativamente menos área superficial del tallo cubierta con esclerocios a 79 DAP, que los testigos no tratados en dos años. No obstante, no se observó el efecto en ambos años en una colecta posterior a 102 DAP, y solo en uno de los dos años a 140 DAP. Se detectaron infecciones latentes en plantas asintomáticas colectadas en el campo.

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“…Infections of the tuber periderm result in gray to brown blemishes in which sclerotia may develop. Tuber shrinkage from water loss (Hunger and McIntyre 1979) and deep sunken lesions (Glais and Andrivon 2004) may occur on tubers in storage.…”

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Response of Colletotrichum Coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation

2011

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“…S. Hughes causes potato black dot, which is named from the sclerotia that develop and macroscopically appear as small, black dots on host tissues. The pathogen causes cortical sloughing of roots, and up to 30% yield reductions have been reported (14,17,37,40). Infected tubers may also exhibit silver to brown lesions and sclerotia which reduces tuber quality, particularly in cultivars destined for the fresh market (33).…”

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Impact of Seed Lot Infection on the Development of Black Dot and Verticillium Wilt of Potato in Washington

et al. 2012

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Dung, J. K. S., Ingram, J. T., Cummings, T. F., and Johnson, D. A. 2012. Impact of seed lot infection on the development of black dot and Verticillium wilt of potato in Washington. Plant Dis. 96:1179-1184.The fungi Colletotrichum coccodes and Verticillium dahliae are two pathogens of potato which are prevalent in potato field soils and seed tubers. The objective of this study was to investigate the influence of seed lot infection by C. coccodes and V. dahliae on disease severity and yield using infested seed lots and fields with and without potato in their recent cropping histories. Greater incidence of C. coccodes in seed led to more root colonization in 2008 (both field types) but not in 2007 and did not influence tuber quantity or yield. Incidence of infection in seed lots by V; dahliae was not related to canopy necrosis.infection of progeny tubers, or yield. However, seed lots exhibited more V. dahliae aboveground vascular colonization, canopy necrosis, infested plant debris, and infected progeny tubers in 5-year potato rotation fields compared with long potato rotation fields. In general, foliar disease symptoms and yield reductions were not related to levels of either pathogen in seed lots. Symptoms of both diseases were more severe and yields were lower in fields with potato in their recent cropping histories, emphasizing the importance of soilborne inoculum in the development of black dot and Verticillium wilt of potato.

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“…Symptoms on tubers were shown to be significantly less frequent in late than early maturing cultivars (Andrivon et al 1997), and black dot symptoms were more common on tubers with a thin periderm than russet tubers with a thick periderm (Hunger and McIntyre 1979). Ranger Russet, the russet cultivar in this trial is used mainly as a short to medium length storage tuber for processing as chips or fries.…”

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Effectiveness of Early-season, Single Applications of Azoxystrobin for the Control of Potato Black Dot as Evaluated by Three Assessment Methods

Cummings

Johnson

2008

Am. J. Pot Res

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Timing of azoxystrobin application for control of potato black dot was evaluated at two to four discrete times during early growth stages of potato from planting to just before row closure in trials from 2003 through 2006. Application timings consisted of a single application of azoxystrobin made either at planting, 34, 43, or 60-62 days after planting. Black dot severity was evaluated on aboveand below-ground stems using three assessment methods. Incidence of infected progeny tubers and yield were also determined. Application at 60-62 days after planting was the most efficacious timing when black dot was evaluated as frequency of detecting Colletotrichum coccodes from 0.5 cm stem sections taken from near the plant crown in 2 of 3 years, as distance of sclerotium expansion on stems in 1 of 2 years, and as sclerotium density on stems 2 of 3 years. Black dot severity was not reduced as evaluated by any of the assessment methods when application of azoxystrobin was made at planting. Below-ground stems had more disease than the above-ground stems as measured by frequency of detection of C. coccodes near the crown 2 of 4 years, distance of sclerotium expansion on stems 2 of 2 years and sclerotium density on stems 3 of 3 years. Disease severity between above-and below-ground stem segments were highly correlated for all disease assessment methods and years except for frequency of detection of C. coccodes from crown tissue in 2005. There were no statistical interactions for any of the disease severity assessment methods between above-and below-ground stem segments with azoxystrobin timing. The sclerotia assessment on above-ground stem segments at end of season was an efficient measure of black dot. Incidence of infected progeny tubers was significantly reduced compared to the non-treated control when application was made at 62 days after planting in 1 of 3 years and at 34 and 43 days after planting in 2 of 4 years. There was not a significant difference in yield between any of the application times and the non-treated control in any year.

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Occurrence, development, and losses associated with silver scurf and black dot on Colorado potatoes

Cited by 32 publications

References 12 publications

Response of Colletotrichum Coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation

Response of Colletotrichum Coccodes to Selected Fungicides Using a Plant Inoculation Assay and Efficacy of Azoxystrobin Applied by Chemigation

Impact of Seed Lot Infection on the Development of Black Dot and Verticillium Wilt of Potato in Washington

Effectiveness of Early-season, Single Applications of Azoxystrobin for the Control of Potato Black Dot as Evaluated by Three Assessment Methods

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