Coffee Rust, also known as Coffee Leaf Rust and in Spanish as “roya,” is a disease of coffee plants that is caused by the fungus Hemileia vastatrix.1–3 H. vastatrix is, as its common name implies, a member of the rusts (FFF#130). Unlike most rusts, however, it has a simple infect-sporulate life cycle, which is likely one reason the disease has been so successful.1 Coffee Rust is a particular problem in Central America, produces 15% of the world’s arabica coffee and exports roughly 432 million kilograms of coffee to the United States annually. The region suffered a devastating outbreak of the disease in the early 2010’s and has yet to fully recover.4–6
fungi in the order Pucciniales
Of all the sexually transmitted infections in the world, the anther smuts are probably the most bizarre. Fungi in the genus Microbotryum infect plants in the pink family (Caryophyllaceae) as well as a few other species. When a plant infected with an anther smut tries to produce flowers, the fungus hijacks the process and forces the plant to make anther-like structures filled with fungal spores instead of pollen. The spores are primarily transmitted to new flowers by pollinators, but can also be spread by wind or splashing raindrops.
Rust fungi – which are so named because of their characteristic, rust-colored spores – have the most complex life cycles of any fungi. These fungi are all obligate plant parasites and most have two hosts. To successfully cycle from one host to the other over the course of a year, rust fungi produce up to five different types of spores.
Unlike most fungal rusts, Cedar-Apple Rust produces large fruiting bodies during one stage in its life cycle. These structures are probably the strangest-looking fruiting bodies found in North America.
Note: This is an archived post. You can find the current version of this post here. Coffee Rust (la roya in Spanish) is a disease of coffee plants that is caused by the fungus Hemileia vastatrix. If you enjoy a fine cup of coffee, then this is one fungus you should be very interested in. The Coffee Rust is currently ravaging coffee trees in Central America, where 60% to 75% of the region’s crops are infected with the pathogen. The result of this has been a 15% drop in Central America’s coffee output and a corresponding loss of more than 100,000 jobs over the last two years. The high-end Arabica trees are particularly susceptible to the disease. America’s major coffee producers have been able to find enough coffee to meet demand without a noticeable impact on price*, but smaller, specialty brewers are having a harder time. And we haven’t seen...