Important diseases: Leaf spot of maple an numerous other plants
Phyllosticta is a very common and important pathogen of numerous plants including woody and herbaceous ornamentals. Phyllosticta only infects plant foliage causing leaf spots. It also can be commonly found as a saprophyte on decaying plant tissue.
Phyllosticta causes small tannish-gray leaf spots with dark, brown to purple borders. Leaf spots are usually small and separate, but sometimes spots can cover large areas of the leaf. Pycnidia (fungal fruiting structures) are produced within the leaf spot, often in a ring pattern.
Pycnidia are light to dark brown in color and partially embedded within plant tissue. Pycnidia contain short, simple conidiophores that produce the fungal spores. Spores are extruded through an opening (ostiole) at the top of the pycnidium.
Conidia are very small, colorless (hyaline) and single celled. Often spores form a "tendril" as they are compressed and extruded through the pycnidia's ostiole. It is difficult to distinguish Phyllosticta from Phoma, another common leaf-spotting fungus.