Pythium root rot

The causal agent of the disease is the oomycete Pythium pulchrum, a soil-borne pathogen belonging to the group of pseudofungi. This microorganism primarily leads a saprotrophic lifestyle, but under favorable conditions, it switches to parasitism, attacking the root system and the root zone of young plants.

This pathogen has a wide host range, infecting both agricultural and ornamental crops. Vegetable seedlings, greenhouse flowers, and certain cereal species are most susceptible to infection, where the parasite causes stunted growth and the death of root hairs.

Symptoms of the infection manifest as darkening, softening, and subsequent rotting of the roots. Externally, this appears as sudden plant wilting, yellowing of lower leaves, and general growth retardation. In high humidity conditions, a white fungal-like growth may develop around the affected areas.

The development of Pythium pulchrum is facilitated by excessive soil moisture, poor drainage, and low temperatures combined with high substrate humidity. The pathogen spreads actively through infested soil, irrigation water, non-sterile tools, and contaminated planting material.

The harmfulness of this oomycete lies in significant stand thinning and a reduction in the marketability of crops. To manage the disease, a comprehensive approach is required:

• Ensuring optimal irrigation schedules and soil aeration.
• Using sterile growing media and healthy plant material.
• Following crop rotation and practicing strict sanitation of tools.
• Applying fungicides from the phenylamide group for chemical protection.
• Biological control using antagonistic microorganisms such as Trichoderma species.