coffee rust, the most devastating disease of coffee plants, caused by the fungus Hemileia vastatrix. Long known in coffee-growing areas of Africa, the Near East, India, Asia, and Australasia, rust was discovered in 1970 to be widespread in Brazil, the first known infected area in the Western Hemisphere. Rust destroyed the once-flourishing coffee plantations of Sri Lanka and Java.
The symptoms of coffee rust include small, yellowish, oily spots on the upper leaf surface that expand into larger round spots that turn bright orange to red and finally brown with a yellow border. The rust pustules are powdery and orange-yellow on the underleaf surface. Later the pustules turn black. Rusted leaves drop so that affected trees are virtually denuded. Such trees usually die within a few years.
Coffee rust is controlled by the timely application of fungicide sprays during wet seasons. Plantations in some areas have been moved to higher and cooler altitudes, 1,800 to 2,100 m (6,000 to 7,000 feet), at which the rust fungus has difficulty reproducing. Quarantine has reduced the chances of coffee rust’s long-distance spread.