Rust, or Rubigo, in vegetable economy, is a disorder affecting certain plants. It consists of a ferruginous powder scattered beneath the leaves, principally of the Ladies-mantle, Stone-bramble, and Ragwort, especially if these vegetables grow in a burnt, woody soil.

Dr. Darwin conjectures the rust to be a fungus, similar to the mildew, which resembles certain kinds of liverwort, and grows beneath the leaves of plants that are previously diseased. He conceives that it may be prevented, or destroyed, by exposing such vegetables to greater light and ventilation, in the manner already described, vol. iii. p. 198.