Cylindrocarpon root rot

Cylindrocarpon root rot is a devastating soil-borne plant disease caused by the fungus Cylindrocarpon destructans (also known as Neonectria radicicola). This pathogen is widely distributed and is known for its ability to persist in the soil for extended periods as chlamydospores, making it a difficult pathogen to eradicate once it is established in a field or greenhouse substrate.

The host range of Cylindrocarpon destructans is notably broad. Among the crops significantly affected are alfalfa (Medicago sativa), red clover (Trifolium pratense), and various ornamental species, including the African violet (Saintpaulia ionantha). The fungus infects the roots, colonizing the cortical tissues and eventually destroying the plant's vascular system.

Symptoms usually begin with the browning and necrosis of the root hairs and lateral roots. As the infection progresses, the primary root system may turn black and become soft due to tissue decay. Above-ground symptoms are characterized by stunted growth, chlorosis, leaf wilting, and in advanced stages, the total collapse of the plant. The roots become dysfunctional and cannot transport water or minerals effectively.

Disease development is heavily influenced by environmental conditions, particularly high soil moisture, poor drainage, and cool to moderate temperatures. Excessive nitrogen fertilization and high soil acidity often exacerbate the severity of the rot. The pathogen spreads rapidly through contaminated soil particles, infected nursery stock, irrigation water runoff, and contaminated farming equipment used across different fields.

Economic damage is significant, often leading to reduced plant density in forage crops and loss of market value for ornamental plants. Effective management requires an integrated approach to sanitation and agronomy:

• Implementing rigorous crop rotation cycles to starve the soil of the pathogen.
• Improving soil aeration and drainage to prevent prolonged saturation.
• Using certified, disease-free planting material.
• Monitoring soil pH and adjusting it to levels unfavorable for fungal proliferation.
• Applying preventative fungicidal treatments or biological control agents to the soil before planting.