Strigulales

Strigulales is an order of fungi within the class Dothideomycetes. While many species within this order are lichenized or live as harmless epiphytes on the surface of leaves, some members can act as plant pathogens. These fungi primarily colonize the surfaces of leaves and stems, often interfering with the host plant's physiological processes by physically blocking sunlight or absorbing nutrients.

The causative agent belongs to the Ascomycota phylum. These fungi are characterized by their slow-growing, often dark-colored mycelium. They are typically classified as foliar pathogens. Although they do not always cause immediate necrosis, their presence can weaken the plant, making it more susceptible to secondary infections or environmental stress factors.

These fungi predominantly affect tropical and subtropical plants, including citrus trees, palms, and various broad-leaved ornamental trees. The pathogen thrives in habitats with high humidity and limited air movement. In commercial orchards, this can lead to reduced yield and poor foliage quality, especially in dense planting systems where light penetration is limited.

Symptoms typically manifest as small, dark spots or crusts on the leaf surface. Unlike many other plant pathogens, the fungal structures, such as perithecia, are clearly visible to the naked eye as minute black dots. As the infection progresses, the surrounding leaf tissue may turn chlorotic or develop necrotic patches, eventually leading to premature senescence and leaf abscission.

Effective management focuses on creating an environment unfavorable for fungal growth. This includes improving orchard ventilation through precise pruning, clearing underbrush to reduce humidity, and monitoring for early signs of infection. If the infestation is widespread, the application of copper-based fungicides or other appropriate chemical treatments is recommended to control the pathogen's development during the rainy season.