Sclerotinia minor

Taxonomy and nature of the pathogen. Sclerotinia minor is a serious soil-borne phytopathogenic fungus belonging to the Kingdom Fungi, Phylum Ascomycota. It is a highly specialized parasite that causes significant agricultural damage globally by attacking the roots and stems of a wide array of dicotyledonous crops.

Diseases and host range. This pathogen is the primary cause of basal stem rot, commonly referred to as white mold. Host plants include a broad range of economically important species such as sunflower, peanut, lettuce, tomato, and various legumes. The disease is characterized by rapid decay of the plant tissue near the soil line, leading to sudden wilting and eventual collapse.

Biology and life cycle. The survival mechanism of Sclerotinia minor is based on the production of small, black, hard resting structures called sclerotia. These structures are resistant to adverse environmental conditions and can persist in the soil for several years. Unlike its relative Sclerotinia sclerotiorum, this species primarily initiates infection through direct mycelial contact from the sclerotia in the soil.

Conditions for development and impact. The fungus thrives in cool, moist soil conditions with temperatures ranging from 15°C to 22°C. Its impact is severe, as it kills the plant by disrupting vascular flow and destroying structural integrity at the base. Yield losses can be substantial, particularly in fields with high inoculum pressure and dense crop stands.

Control and management measures. Integrated pest management (IPM) is essential to minimize the impact of the pathogen in agricultural systems:

• Crop rotation with non-host crops, such as cereals or corn, to reduce inoculum levels.
• Deep plowing to bury sclerotia at depths where they are less likely to germinate and infect.
• Application of chemical fungicides targeting the base of the plant during the early growth stages.
• Improving soil drainage to prevent excessively moist conditions that favor fungal growth.
• Use of biological control agents, particularly mycoparasitic fungi like Coniothyrium minitans.