Ustilaginoidea virens

Ustilaginoidea virens, perfect sexual stage Villosiclava virens, is a plant pathogen which causes the disease "false smut" of rice which reduces both grain yield and grain quality. The disease occurs in more than 40 countries, especially in the rice producing countries of Asia. but also in the U.S. As the common name suggests, it is not a true smut (fungus), but an ascomycete. False smut does not replace all or part of the kernel with a mass of black spores, rather sori form erupting through the palea and lemma forming a ball of mycelia, the outermost layers are spore-producing. Infected rice kernels are always destroyed by the disease. Of particular concern are the production of alkaloids in the grain as with the Claviceps spp. causing ergot however U. virens is not a Claviceps/ergot fungus, is not known to produce ergotism, and lacks enzymes necessary in ergot synthesis. Although U. virens does infect maize/corn, it does not do so often, produce significant disease, or have economic consequences.

from Wikipedia