Ergot of rye is caused by a species of

Ergot of rye is a plant disease caused by the fungus Claviceps purpurea, a member of Ascomycetes.
The fungus infects the ovaries of the rye flowers. The so-called ergot that replaces the grain of the rye is a dark, purplish sclerotium, from which the sexual stage of the life cycle forms after overwintering.
The sclerotia contain poisonous alkaloids; eating bread made from infected grain causes the disease ergotism. The hallucinogenic drug LSD is also derived from ergot alkaloids.
Uncinula causes powdery mildew of grapes.
Ustilago causes smut diseases of cereals.
Phytophthora infestans causes late blight of potato.
So ergot of rye is caused by a species of Claviceps.