Strigula elegans

Strigula elegans is a specialized type of foliicolous lichen that colonizes the surface of leaves in evergreen plant species. Within the agricultural sector, while biologically defined as a lichen, it is often classified as a plant health concern because it disrupts the photosynthetic capacity of host plants by forming a physical layer on the leaf surface, thereby hindering sunlight absorption and gas exchange.

This organism frequently impacts tropical tree plantations, with Indian mango (Mangifera indica) being a primary host of economic significance. Besides mango, various citrus species and other tropical ornamentals growing in high-humidity habitats are susceptible to colonization, which can lead to reduced vigor and productivity of the trees.

Symptoms of infestation are identified by the appearance of thin, grayish, or greenish-white spots on the leaf blades. These spots are usually circular or irregular in shape and adhere firmly to the cuticle. While the lichen does not destroy leaf tissue immediately, it creates an unfavorable environment on the leaf surface, which can predispose the plant to secondary infections and cause premature senescence of affected leaves.

The development and spread of Strigula elegans are heavily dependent on environmental conditions, specifically high relative humidity and consistent warmth. Dense canopy structures and poor airflow within the orchard significantly facilitate the colonization process. Once spores settle on a leaf, they rapidly develop into thalli, especially in areas where leaves remain damp for extended periods.

• Regular pruning to enhance airflow and light penetration into the tree canopy.
• Sanitation measures, including the removal of heavily infested plant parts.
• Proper orchard management to avoid overcrowding and maintain tree spacing.
• Application of copper-based fungicides during humid periods, if necessary.
• Monitoring for early signs of lichen colonization to manage spread effectively.