Potato Streptomycosis

The causative agent of this plant disease is the soil-borne actinobacterium Streptomyces olivaceus, which is a common member of the complex causing common scab in potatoes. This pathogen exists primarily as a saprophyte in the soil, but it can switch to a parasitic mode when conditions allow it to infect the periderm of underground plant organs.

The disease primarily targets potatoes, but it can also affect other root crops such as carrots, beets, and radishes. The presence of the bacteria causes significant economic loss, as affected tubers lose their marketability and are more susceptible to weight loss and spoilage during long-term storage.

The symptoms of the infection appear as localized lesions on the tuber surface. These lesions may manifest as superficial russeting, raised corky scabs, or deep, pitted craters. As the disease progresses, these individual lesions can merge, covering a large portion of the tuber's surface and creating a rough, unattractive appearance.

Environmental conditions play a critical role in the development and spread of Streptomyces olivaceus. The bacteria thrive in neutral to alkaline soils with a pH level above 6.0. Furthermore, dry conditions during the critical early stages of tuber initiation are highly favorable for the pathogen to successfully infect the young skin of the tubers.

Control strategies for managing this pathogen focus on integrated pest management practices. Key preventative measures include avoiding the planting of potatoes in fields with a history of severe scab, maintaining soil acidity through appropriate fertilization, and ensuring consistent moisture levels during tuber development. Selecting resistant cultivars remains the most effective long-term strategy for producers.