Olpidium

Olpidium is a genus of plant-pathogenic fungi known to cause root diseases in a wide range of horticultural and agricultural crops. These fungi are obligate parasites that thrive in soil and water, primarily targeting the roots of plants by invading epidermal cells to complete their life cycle.

The disease frequently impacts vegetables such as cabbage, lettuce, and cucurbits, often becoming a major issue in seedling production. Because these pathogens can survive in the soil for extended periods, they pose a significant threat to greenhouse environments where crop rotation is limited.

Key symptoms include stunting, chlorosis of the lower leaves, and wilting during the day, which often recovers at night. If the roots are examined, they typically show signs of browning or necrosis, and the fine root system may be underdeveloped or absent due to the aggressive nature of the infection.

Transmission of Olpidium occurs primarily through motile zoospores that swim through the soil solution or irrigation water. Environmental conditions characterized by high humidity, poor drainage, and cool temperatures are ideal for the rapid spread of the pathogen throughout a greenhouse or nursery block.

Integrated management is essential for control, as chemical options can be limited. Preventive practices such as steam sterilization of soil, improving drainage systems, and using high-quality disease-free seedlings are highly recommended. Maintaining proper plant spacing and avoiding water saturation helps significantly to reduce the risk of outbreaks.