Hypomyces lateritius

Hypomyces lateritius, the ochre gillgobbler, is a parasitic ascomycete fungus that grows on certain species of Lactarius mushrooms, improving their flavor and densifying the flesh. Hosts include L. camphoratus, L. chelidonium, L. controversus, L. deliciosus, Lactarius indigo, L. rufus, L. salmonicolor, L. sanguifluus, L. semisanguifluus, L. tabidus, L. trivialis, and L. vinosus. It is a microscopic fungus causing the formation of a macroscopic whitish subiculum over the hymenium of its host species, preventing gill formation. Presence of H. lateritius also often deforms the cap and stipe. Parasitization by H. lateritius does not prevent latex from forming when the flesh is cut....read more on Wikipedia.