Rhipidiaceae fungi

The Rhipidiaceae family belongs to the order Leptomitales and represents a group of aquatic oomycetes. While most members of this family are saprotrophic, living on decaying organic matter in water and moist soil, some species exhibit phytopathogenic properties, affecting the root system and the root zone of various higher plants.

The pathogens are microscopic organisms characterized by a well-developed mycelium with pseudosepta. During their development, they produce sporangia that release zoospores capable of active movement in aquatic environments. The presence of these motile stages makes them particularly dangerous for crops grown in hydroponic systems or in waterlogged soil conditions.

These oomycetes most frequently affect vegetable and ornamental crops grown in greenhouse hydroponic systems, as well as seedlings in open fields during periods of excessive watering. The root system becomes the primary target of the pathogen, where it causes tissue destruction, which prevents the plant from absorbing nutrients and water effectively.

Symptoms of infection include darkening and softening of the roots, overall stunted growth, leaf chlorosis, and subsequent wilting, which is often misdiagnosed as a nutrient deficiency. Close inspection of the root collar may reveal a specific mycelial growth, common in conditions of water stagnation and poor substrate aeration.

Control measures are based on strict monitoring of substrate moisture and water quality. Key preventive methods include regular disinfection of hydroponic equipment, the use of high-quality pathogen-free planting material, and maintaining conditions that hinder pathogen growth. It is essential to prevent waterlogging and ensure adequate drainage, as water stress is a primary factor triggering the activation of Rhipidiaceae spores.