Caliciopsis arceuthobii

Caliciopsis arceuthobii, also known as dwarf mistletoe smut, is a species of fungus in the Coryneliaceae family. It parasitizes the pistillate (female) flowers of four species of North American dwarf mistletoes in the genus Arceuthobium. Since mistletoe is itself a parasitic plant, C. arceuthobii is a hyperparasite. Its rough, black fruiting bodies appear near the tips of the mistletoe fruit, whose development it disrupts. Because of its effects on mistletoe populations, which have serious impacts on forest ecology, C. arceuthobii has been considered as a possible biological control agent.