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 are light to dark brown in color and partially embedded within plant tissue.
Pycnidia contain short, simple conidiophores that produce the fungal spores.
It is difficult to distinguish Phyllosticta from Phoma , another common leaf-spotting fungus.