Common scab

Common scab is a significant bacterial disease affecting a wide range of root and tuber crops, caused by filamentous bacteria of the genus Streptomyces. These soil-borne pathogens are known for their ability to thrive in various environments, surviving as saprophytes on decaying organic matter in the absence of suitable host plants.

The disease impacts numerous crops, including potatoes, fodder beets, winter rapeseed, turnips, peanuts, soybeans, and citrus species. The infection process typically begins during the early stages of tuber or root development, when the pathogen colonizes the skin of the plant through lenticels or small wounds.

Symptoms are characterized by the appearance of unsightly lesions, scabs, or deep pits on the surface of harvested produce. Depending on the crop variety and environmental conditions, these lesions can range from superficial russeting to corky, raised growths that significantly reduce marketability and consumer appeal.

Development and spread of the disease are highly dependent on soil conditions. Streptomyces species generally prefer well-aerated, sandy soils with a neutral to alkaline pH (ranging from 6.0 to 7.5). Low soil moisture levels during the early stages of tuber formation are particularly conducive to severe outbreaks of the disease.

Management strategies focus on preventive agronomic practices. Essential measures include maintaining optimal soil moisture during tuber initiation, rotating crops with non-host species, and using acidifying fertilizers to lower soil pH. Additionally, selecting resistant varieties and avoiding over-liming of the soil are critical steps in reducing the incidence and severity of the disease in agricultural fields.