rubigo

/ruːˈbaɪɡoʊ/
noun
  1. A reddish or rusty coating or stain, especially on plants caused by rust fungus.
    • The gardener noticed rubigo on the leaves of the rose bushes.
    • The old iron gate was covered in rubigo from years of exposure to moisture.
    • Rubigo spread quickly across the wheat field after the rainy season.
Synonyms
What does "rubigo" mean? | whatsthatwordmean | whatsthatwordmean