Mortierella polycephala

Mortierella polycephala is a microscopic soil-borne fungus classified under the Zygomycota phylum. While primarily recognized as a saprotrophic organism involved in organic matter decomposition within the rhizosphere, it can exhibit pathogenic behavior under specific environmental conditions, potentially causing root diseases and damping-off symptoms in young plants.

The fungus predominantly affects seedlings and young horticultural crops. Its impact is most significant in greenhouse environments, where high humidity and temperature profiles create an ideal niche for fungal development. Crops such as vegetables and ornamental flowers are particularly susceptible during their early growth stages.

Symptoms of an infection include stunted plant growth, leaf chlorosis, and sudden wilting. A critical diagnostic feature is the decay and browning of the root system, often accompanied by a white, cottony mycelial mat visible on the soil surface around the plant stem. In severe infestations, the root system may completely disintegrate, leading to plant mortality.

The development and spread of the fungus are triggered by excessive soil moisture, poor aeration, and compact substrate conditions. The pathogen can survive in the soil for extended periods as spores, resisting various environmental stressors, which allows it to persist in fields and greenhouses across growing seasons.

To mitigate the risk of disease, growers should implement the following strategies:

• sterilize growing media and containers before planting;
• maintain optimal moisture levels and ensure excellent drainage;
• apply systemic fungicides as a preventative seed treatment;
• improve air circulation and greenhouse ventilation;
• immediately remove and dispose of any infected seedlings to prevent secondary spread.