​​​Blemishes of Table Potatoes: Common Biotic Causes

March 2016 | 21 min., 34 sec.
by Jacquie van der Waals
University of Pretoria


​Although many blemishes on potato tubers are merely cosmetic, the demand by consumers for washed potatoes has exacerbated the problem of rejection of blemished tubers. Tuber blemishes are broadly classified as typical or atypical. Correct diagnosis of a tuber blemish is important in managing the disease and preventing future occurrences. This presentation covers the causal agents, symptoms, and management of the most common tuber blemishes with biotic causes. It can serve as a guide for growers and others in the potato industry to help with identifying these blemishes. 

About the Presenter

Jacquie van der WaalsJacquie van der Waals began research on potatoes in 1998 and earned her PhD at the University of Pretoria, South Africa, on the epidemiology of early blight on potatoes. She is an associate professor in the Plant Pathology section of the Department of Plant Science at the University of Pretoria. The main emphasis of her program is those potato pathogens that are most difficult to control, namely, soil- and seedborne pathogens: specifically, Pectobacterium and Dickeya (soft rot–blackleg disease complex); Spongospora subterranea f. sp. subterranea (powdery scab); Rhizoctonia solani (black scurf); and Streptomyces species (common scab). These diseases are rapidly becoming the biggest threats to sustainable potato production globally due to intensification of production and the dwindling amount of virgin soils available. Dr. van der Waals’s research focusses on understanding the complex interactions of these potato pathogens with one another and their host, with the ultimate goal of integrated management of all diseases affecting potatoes.

Contact Information:
Email: Jacquie.vanderWaals@up.ac.za


In 2020, Grow webcasts had more than 110,000 views. Help support our mission to provide comprehensive high-quality, science-based resources to and for plant health researchers and practitioners at no cost.

PDMR submission guidelines and schedule information are available online.


Plant Health Progress is a peer-reviewed multidiciplinary, online journal of applied plant health.