Pythium root rot

The causative agent of the disease is the oomycete Pythium polymastum, a widespread soil-borne pathogen. This organism thrives in the rhizosphere, specifically targeting the roots of plants and interfering with their ability to uptake water and essential soil nutrients, ultimately leading to plant decline.

This pathogen primarily affects a wide range of vegetable crops, ornamental plants, and seedlings. Young, developing root systems are particularly susceptible, as the pathogen exploits soft tissue, which makes seedling stages the most dangerous period for potential infection in professional nurseries.

Symptoms of the infection include root discoloration, where roots become brown, soft, or mushy upon inspection. The aerial parts of the infected plant exhibit signs of drought stress despite adequate soil moisture, including wilting, chlorosis, and significantly stunted growth, which often progresses to complete collapse.

The development of Pythium polymastum is heavily promoted by waterlogged conditions and poor soil aeration. These environments provide the necessary moisture for the motile zoospores to spread through the soil. Cooler soil temperatures coupled with high humidity often trigger severe outbreaks in greenhouse conditions.

Effective management and protection strategies include:

• Ensuring excellent soil drainage to avoid water accumulation.
• Practicing strict crop rotation schedules.
• Steam or chemical sterilization of greenhouse substrates.
• Application of biological control agents such as Trichoderma spp.
• Monitoring irrigation practices to prevent overwatering.