Trichotheliaceae

Trichotheliaceae is a family of lichenized fungi that are often misidentified as plant diseases. It is crucial to distinguish them from pathogenic fungi: they are epiphytic organisms that do not derive nutrients from the host plant's tissues, nor do they invade the plant's vascular system to cause decay or disease.

The biology of these organisms is based on a mutualistic symbiosis between fungi and algae (or cyanobacteria). They grow on the surface of bark, leaves, or twigs, primarily serving as indicators of the local environment's humidity and air quality. In agricultural settings, they are commonly found on the trunks of older fruit trees that have not been pruned or maintained for long periods.

While Trichotheliaceae are not pathogenic, their presence can be considered a sign of poor orchard maintenance. A thick layer of lichens can retain moisture against the bark for extended periods, potentially creating a micro-environment suitable for wood-boring insects, scale insects, or secondary bacterial pathogens that exploit existing wounds in the bark.

Symptoms of colonization include the appearance of crustose or foliose patches with varying colorations, ranging from pale gray to vibrant green, depending on moisture levels. These structures adhere firmly to the substrate, and under high humidity, they may appear soft or gelatinous. Unlike pathogenic fungi, they do not cause necrosis or discoloration of the underlying bark tissue.

Integrated management practices are the most effective way to address the overgrowth of these lichens. Recommended steps include maintaining proper tree vigor through balanced fertilization, ensuring adequate spacing and pruning to facilitate airflow, and periodic mechanical removal of dead bark tissue. Chemical control is generally unnecessary, as the focus should remain on improving the plant's overall health and vitality.