Pink rot (Phytophthora erythroseptica)

Pink rot: biology

Pink rot is a devastating soil-borne disease caused by the pathogen Phytophthora erythroseptica that thrives in wet, poorly-drained soils. Every field has the potential for pink rot, and it only takes a very small number of infected tubers going over harvest equipment or getting by on the belt to result in substantial storage losses.

Pink rot survives in the soil as mycelia and special overwintering spores called oospores. The spore swims through the watery film in or on the soil to infect stems below the soil surface, stolons or roots. Once a plant is infected, the pathogen can grow into the tuber. In wet, poorly drained areas, tubers can also be infected through the eyes or lenticels.

Pink rot can affect both plants and tubers.

Symptoms include wilting, usually in late season. Aerial tubers may form. Brown spots develop on potato skins and the flesh becomes soft and mushy and turns pink when cut. A clear line can be drawn between healthy and diseased areas of infected tubers.

Infected tubers often decay during harvest and handling, allowing the infection to spread rapidly to healthy tubers during storage.