A fungus called hemileia vastatrix causes a plant disease called coffee leaf rust. It affects the two major commercial species of coffee, Coffea arabica and Coffea canephora, and likely many other coffee species.
Coffee leaf rust causes yellow spots to form on the leaves of coffee plants, and eventually, lesions that cause the leaves to drop from the plant prematurely; it devastates the bean harvest. There is no cure for the disease and attempts to thwart it may only be encouraging resistant varieties to evolve.
First discovered by westerners in 1861, this devastating fungus has been creating a crisis in Latin America. An outbreak that began in the coffee-producing region in 2012 has spread, with up to seventy percent of farms now affected, and an estimated 1.7 million farmhands out of work.