Plant fungus is a type of fungus that affects plants and can cause serious damage to crops. SMUT is a type of plant fungus that causes black spots on the leaves and stems of plants. ERGOT is another type of plant fungus that can cause grain to become toxic and can be fatal if consumed. RUST is a type of plant fungus that causes orange or yellow spots on the leaves and stems of plants. All three types of plant fungus can cause significant damage to crops and can have a major impact on food production.