Pseudopithomyces chartarum

Pathogen and disease type. Pseudopithomyces chartarum is a saprophytic fungus that acts as an opportunistic plant pathogen. It primarily colonizes dead organic matter found in the litter layer of pastures and crop fields. While its primary impact is often associated with the production of toxins, its presence marks a degradation in plant health and pasture quality.

Susceptible crops and symptoms. The fungus affects a wide range of grasses, legumes, and cereals. Symptoms on plants are often subtle, appearing as necrotic spots or dark, sooty mold patches on the lower, decaying parts of the foliage. In many cases, the fungus remains inconspicuous until environmental conditions trigger a massive release of spores across the crop canopy.

Development conditions. The lifecycle and proliferation of the fungus are heavily influenced by climate. It thrives in high-humidity environments, specifically when there is persistent surface moisture or dew combined with temperatures consistently between 18°C and 25°C. These conditions promote rapid mycelial growth and sporulation on decaying organic debris.

Economic impact. The primary concern is not direct yield loss in the classical sense, but the formation of sporidesmin. This mycotoxin causes severe liver damage and photosensitivity in grazing animals, a condition known as facial eczema. Consequently, the presence of the fungus significantly decreases the grazing utility and safety of affected agricultural lands.

Control and prevention. Managing the threat requires a combination of careful land use and sanitation practices:

• Frequent mowing to reduce the accumulation of decaying organic matter.
• Strict grazing management to avoid consuming the base layer of the pasture.
• The use of resistant plant species or cultivars in high-risk areas.
• Monitoring weather patterns to predict spore outbreaks.
• Applying fungicides when environmental thresholds for sporulation are exceeded.