Potato Scab

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Potato Scab

Streptomyces scabies


In a Nutshell

  • No symptoms in aerial parts of the plant.
  • Brown, corky blisters on surface of potato.
  • Shallow-to-deep holes and net-like cracks on the potato tuber.




No symptoms are visible on the aerial parts of the plant such as leaves, stalks or petioles. However, the pathogen causes a series of symptoms on the surface of the potato tuber. They can range from reddish-brown raised corky skin, to pitted surfaces with shallow-to-deep holes, to a net-like series of cracks in the upper layer of the potato skin. This results in yield losses and reduced quality of the potato tubers.


Scabies survives in the soil as spores in infected tissue. It enters plants through wounds. Dry and warm weather during the period of tuber growth increases the infection risk. Since the bacteria need large amounts of oxygen, the probability of infection is higher in loose and well-ventilated soils. The bacteria are most prevalent in dry and alkaline soils.

Biological Control

Treatment of potato plants with compost, compost tea or a combination of both significantly reduces the severity of common scab tuber disease. Bio-fertilizers based on competitive strains of bacteria can increase both yield and the quality of the tuber.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Chemical treatment of potato scab is difficult, because it often causes plant injuries. Seed treatments with fluazinam, chlorothalonil and mancozeb showed the lowest percentage of infection.

Preventive Measures

Plant tolerant varieties.,Ensure well-coordinated field rotation.,Maintain good soil moisture with regular irrigation and avoid over-watering.,Keep soil pH levels low with a specific fertilization scheme.,For example, apply elemental sulfur, gypsum or ammonium sulfate to maintain a low soil pH and reduce the severity of the disease.,Do not lime before planting.