Olpidium root rot

The disease is caused by the soil-borne chytrid fungus Olpidium brassicae, an obligate parasite. This pathogen infects the root systems of various plant species, including crucifers, lettuce, and certain legumes such as peanuts. It primarily spreads through contaminated soil, irrigation water, and infected transplant seedlings.

The primary concern regarding this pathogen is its role as a vector for various plant viruses, such as lettuce big vein virus. Beyond acting as a virus carrier, the fungus itself invades root tissues, which weakens the plant's ability to absorb water and nutrients, leading to stunted growth and reduced yields.

Symptoms typically manifest as yellowing of the lower foliage, overall wilting during warm periods, and retarded development. Below the soil surface, the roots exhibit darkening, tissue decay, and necrosis of the fine root hairs, which significantly hampers the plant's physiological processes.

Favorable conditions for the spread of the disease include high soil moisture, poor drainage, and cool to moderate temperatures. The fungus produces resting spores that remain viable in the soil for several years, making it difficult to eradicate once it has become established in the field or greenhouse environment.

Effective management strategies include crop rotation, the use of disease-free planting material, and rigorous sanitation practices. In greenhouse settings, steam sterilization of soil or the use of specific fungicides can reduce inoculum levels.

• Improving soil drainage systems;
• Cleaning tools and machinery;
• Avoiding over-irrigation.