Gymnosporangium juniperi-virginianae is a rust fungus known as Cedar-Apple Rust (sometimes abbreviated to CAR) that causes disease in Eastern Red Cedar and in apple trees. This fungus is unique among rusts because it produces large fruiting bodies. On cedar trees, the fruiting bodies resemble lumpy brown golf balls with long gelatinous orange tentacles bursting out of them. On apple trees, the disease causes more damage but produces only orangish spots. The complex life cycle of Cedar-Apple Rust means the fungus is easy to control, although these control methods resulted in a legal case that was argued before the Supreme Court of the United States!
fungi in the order Pucciniales
Wheat is the most widely grown crop in the world and is a staple food for billions of people. Diseases affecting wheat are therefore of utmost importance to food security. Some of the most destructive and difficult wheat diseases are the rusts. Wheat rust comes in three varieties: Leaf Rust, Stem Rust, and Stripe Rust, each caused by a different species of fungus. These all look slightly different but all cause rust-colored blemishes on wheat surfaces. The three species are closely related and have nearly identical life cycles. Despite this, managing the diseases is complicated and requires using resistant wheat strains, proper cultural practices, and fungicides.
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
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.
Note: This is an archived post. You can read the current version of this post here. 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...