Research reports on potato blemish diseases

AHDB Potatoes funded research projects on the biology and management of scurf, scab and black dot diseases of potatoes. 

Some reports refer to pesticides that may no longer be used in GB. Please refer to the Health and Safety Executive, Chemicals Regulation Division (CRD) website for up-to-date information on the plant protection products authorised for use in GB.

Click on a project title below to see more information and download the final report

Potatoes Independent Variety Trials (IVT) programme (2002-2018)

  • pot trials to assess varietal susceptibility to black dot, (black scurf), silver scurf, skin spot

807/131 Resistance to potato blemish diseases (1997-2001)

The final report from this project is provided at the bottom of the IVT page

  • develop reliable methods to identify varietal resistance to Helminthosporium solani, Colletotrichum coccodes and Rhizoctonia solani
  • study the genetics of resistance with the aim of improving levels of resistance in potato germplasm
  • study the variability between isolates of each of the pathogens, including their fungicide sensitivity

R422 Informing management of potato diseases through epidemiology and diagnostics (2009-2012)

  • to improve risk assessment for powdery scab, Rhizoctonia and common scab using diagnostics
  • problems with soil sampling for R. solani
  • reviews of R. solani biology, symptoms and management

R253 Improving decision making for the management of potato diseases using real-time predictive diagnostics (2004-2008)

  • includes work on diagnostic assays for Rhizoctonia, black dot, powdery scab
  • relationship between pathogen inoculum levels on seed and/or in soil and disease
  • review of soil sampling strategies

R280 Literature review: the use of plant resistance to manage potato pests and diseases (2007)

  • variety resistance to blemish diseases

R278 Literature review: preserving skin finish during storage (2006)

  • blemish disease control (black dot, silver scurf, skin spot)


Black dot

caused by Colletotrichum coccodes

R249/R400 Developing effective integrated control measures for the control of black dot (2004-2009)

  • real-time PCR diagnostic test to quantify the level of Colletotrichum coccodes in soil and tubers
  • role of seed vs soil inoculum in causing disease
  • crop duration and soil inoculum to and risk of black dot developing during storage
  • measurements of crop stress
  • impact of post-harvest storage regime on disease development

 807/222 Improving the understanding and management of skin set, bloom and netting in potatoes (2001-2005)

  • crop duration and black dot levels


Black scurf

caused by Rhizoctonia solani

See R422 for reviews of Rhizoctonia biology, symptoms of infection and predicting disease risk based on seed and/or soil inoculum

R411 Extending the Scope of Modern Potato Diagnostics and their Interpretation (2008-2009)

  • soil sampling for R. solani

807/232 Detection and distribution  of soil-borne  Rhizoctonia solani causing black scurf and stem canker in potatoes (2002-2004)

  • soil sampling and comparison of diagnostic methods


Skin spot

caused by Polyscytalum pustulans

R251/R413 Skin spot of potatoes: diagnostics and fungicide efficacy (2004-2010)

  • literature review (2004)
  • development of a diagnostic assay for Polyscytalum pustulans and its use in skin spot risk assessment
  • comparison of fungicide application methods & disease control

 R285 /R294 Determining the ability of a novel quantitative PCR assay to detect latent infections of Polyscytalum pustulans and its use as an early indicator of skin spot risk (2007-2008)

  • development of real-time PCR assay to detect the quantity of pathogen-specific DNA detected in tuber peel

 R284 Evaluating the efficacy of a screen humidity cell in filtering pathogens and other particulates out of air in potato stores (2006)

  • refers to removal of  P. pustulans spores from store atmospheres


Silver scurf

caused by Helminthosporium solani

R457 Improved store management of diseases affecting seed tubers and its effects on the subsequent crop (2011-2012)

  • effects of different storage regimes on seed-borne diseases including silver scurf


Common scab

caused by pathogenic Streptomyces species

11140047 Review of Liming, pH and Common Scab Risk in Potatoes (2018)

  • review of relationship between common scab, pH, liming and calcium in potatoes

R448 Common scab control - reducing the irrigation water requirements and understanding the effects of beneficial soil microorganisms (2011 - 2014)

  • irrigation scheduling for salad crops and varieties less susceptible to common scab than Maris Piper
  • mechanisms by which irrigation reduces the population build-up of pathogenic Streptomyces
  • effects of beneficial soil micro-organisms and biofumigation
  • soil structure within the ridge/bed and optimal irrigation regimes for scab control
  • effects of over-watering on crop growth, tuber quality and nitrogen use efficiency

R429 Effect of contrasting irrigation regimes on populations of Streptomyces and potential antagonists and control of common scab (2009-2010)

  • DNA sequencing used to identify groups of microorganisms which may be responsible for suppression of scab
  • field experiments with five different irrigation regimes. Weekly sampling of tubers one to five weeks after tuber initiation to determine Streptomyces populations, and at harvest to measure yield and levels of scab

 R272 Integration of precision irrigation and non-water based measures to suppress common scab of potato (2006-2009)

  • no consistent effects of non-water based control measures (soil amendments with sulphur or rapeseed meal) or common scab

 R248 Review of research on non-water-based approaches to control of potato common scab (2004)

  • the Streptomyces species causing disease
  • knowledge on 12 non-water control options

A supplement to the review (written in 2005) covers the potential to use manganese to control common scab, possible biocontrol agents and the effect of organic ammendments on common scab control


Powdery scab

caused by Spongospora subterranea

R411 Extending the Scope of Modern Potato Diagnostics and their Interpretation (2008-2009)

  • diagnostics to monitor infection and disease development

 R262 Literature reviews on powdery scab of potatoes (2008)

  • soil properties and disease risk

807/211 Epidemiology, autecology and control of Spongospora subterranea, cause of potato powdery scab (1999-2002)

  • viability of S. subterranea sporeballs over time
  • pathogen inoculum level (soil or seed), environmental factors and disease (powdery scab and root gall development)
  • varietal resistance

R421 PhD: Spongospora subterranea genetic diversity (2009-2012)

  • 700 samples (from tuber lesions or root galls) analysed using molecular techniques


Potato Mop Top Virus (PMTV)

The projects on PMTV have been provided as the virus is transmitted by Spongospora subterranea

R291 Testing potato varieties for susceptibility to PMTV (2007-2008)

  • to assess if field trials using naturally infested soils can be used to provide reliable information on variety susceptibility to PMTV

R247 The importance of potato mop top virus (PMTV) in Scottish seed potatoes (2004-2007)

  • the role of the powdery scab pathogen in PMTV infection
  • the transmission rate from mother to daughter tubers
  • the relative contribution of seed and soil inoculum to disease development
  • the effect of PMTV on yield and quality


Identify blemish diseases and their symptoms