Phyllosticta minima is a fungus of the division Ascomycota which causes purple-bordered leaf spot, a largely cosmetic disease that infects maple trees.

[1] It grows on living and fallen leaves, creating tan, ovular lesions 1⁄4 inch in diameter and ringed with 'purple' or black spores.

If the purple-bordered leaf spot is persistent for several years or adversely affecting a young tree, a fungicide containing copper, neem oil, sulfur, chlorothalonil or thiophanate-methyl can help manage the fungus.

The best form of management is planting resistant strains (purple-bordered leaf spot most heavily infects Amur, Japanese, red, silver and sugar maples).

Additionally, it is important to remove, burn or bury leaf litter from infected trees in the fall or early spring, as this is where the spores overwinter.