A type of fungus that grows on plants, especially on wheat and other grains.
Rubigo is not good for plants and can make them sick.
Examples:
The rubigo is on the wheat.
The farmer doesn't like rubigo.
Rubigo can make the plants sick.
Rubigo is like a plant's cold.
The rubigo is everywhere, making all the plants sick.
Rubigo is a bad thing for plants.