Meaning of orange rust

or'ange rust'

Pronunciation: [key]
— Plant Pathol. Plant Pathol.
  1. a disease of blackberries and raspberries, characterized by an orange, powdery mass of spores on the undersides of the leaves and stunted, misshapen foliage, caused by a rust fungus, Gymnoconia interstitialis.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.