Pink root

Pink root is a destructive soil-borne fungal disease caused by the pathogen Setophoma terrestris (formerly Pyrenochaeta terrestris). This fungus primarily attacks the root system of plants, disrupting their ability to absorb water and essential nutrients from the soil.

The disease is most notably associated with onion crops, although it can affect a variety of other vegetable species. The fungus is a persistent soil inhabitant, capable of surviving on decaying plant debris for several years even in the absence of a susceptible host, which makes it a persistent challenge in agricultural production.

The primary symptom, which gives the disease its name, is the characteristic pink discoloration of the roots. As the infection progresses, the affected roots shrivel, turn dark brown or black, and eventually die. Consequently, plants exhibit stunted growth, leaf tip dieback, and reduced bulb development, leading to significant yield losses.

The development of the disease is highly dependent on environmental factors, specifically soil temperature and moisture. Setophoma pathogens thrive in warm soil conditions, typically ranging between 24°C and 28°C (75–82°F). High soil moisture levels, combined with the lack of proper crop rotation, provide the ideal environment for rapid infection spread.

Managing pink root requires an integrated approach to reduce the pathogen population in the soil. Key prevention strategies include:

• Implementing long-term crop rotation cycles (4–5 years).
• Using resistant or tolerant onion cultivars.
• Maintaining optimal soil drainage to prevent water stagnation.
• Implementing soil solarization or fumigation where economically viable.