Exophiala mycosis

The disease is caused by the fungus Exophiala jeanselmei, a dematiaceous (black) yeast-like pathogen. It is recognized as an opportunistic fungus that thrives in environments where plants are stressed or weakened. In agricultural settings, it is primarily identified as a causal agent of root rot and vascular necrotizing diseases affecting various greenhouse and indoor plant species.

This pathogen demonstrates a high affinity for decorative and ornamental plants grown in protected environments. It can also affect certain vegetable crops. Its presence is often linked to the physical degradation of root structures, which significantly hinders nutrient and water uptake from the growth medium.

Symptomatology involves the development of dark brown to black lesions on roots, rhizomes, and the base of stems. As the infection progresses, these areas become necrotic and soft. The foliage often displays signs of chlorosis and wilting due to the impairment of the vascular system, preventing the upward movement of water and dissolved nutrients.

Environmental conditions such as high humidity and poor soil aeration are the primary drivers for the proliferation of Exophiala jeanselmei. The fungus is highly resilient, capable of persisting in the soil and contaminated media for long periods through the production of dormant structures, such as chlamydospores, which resist many environmental stresses.

Management of this pathogen focuses primarily on sanitation and environmental control, as curative measures for internal plant infections are limited. Essential strategies for prevention include:

• Sterilizing growing media and pots before planting.
• Maintaining proper drainage to prevent waterlogging of the root zone.
• Regular inspection of plants for early signs of decay.
• Strict hygiene protocols regarding tools and equipment to prevent cross-contamination.
• Application of appropriate fungicides only as a preventative measure in high-risk environments.