Bean killer #1: coffee rust

Coffee rust? It’s real and it’s attacking your favorite coffee plants. Okay, that was a bit dramatic. While true, the situation isn’t quite as apocalyptic as you may have been lead to believe — though coffee rust does threaten global coffee supply, particularly Central American coffee, it does not signal the end of coffee.

Coffee rust is a rust colored fungus, technically known as hemileia vastatrix, that grows on coffee plants, depriving them of essential nutrients and eventually choking them. Coffee rust is not a new fungus; it is a primitive fungus believed to have originated alongside the coffee plant. We are hearing more about coffee rust now because its proliferation is exacerbated by global warming, threatening specialty coffee and driving up coffee prices as farmers suffer reduced or lost crops due to rust. According to studies, as of October 2018, up to 70% of Central America’s arabica plants had been infected by rust resulting in financial losses exceeding $3 billion and industry job losses of nearly 2 million1. To put this in perspective, Central American coffee comprised 10% of the 2018 global arabica supply2 — coffee does, however, account for over 50% of some Central American nations’ annual exports. On a macro level, coffee rust isn’t a critical problem but on a microlevel (e.g., to the GDP of El Salvador), it can be devastating.

Documented and studied as early as 1861, there is no known cure for coffee rust. Historically, cool evenings and healthy plants have been enough to either fend off or kill off this nutrient-starving fungus. With global warming, evenings are warmer, allowing the rust to survive and spread. Today, farmers must exercise greater vigilance in maintaining their plants’ health and attempt to curb rust at its first appearance. The appearance of rust is not a death sentence to the plant but it is a strong warming. Unlike fast-attacking diseases, coffee rust is a slow, multi-year death for a plant that begins with the development of yellow spots on the plant’s lower leaves and ends, if not curbed, with most of the plant’s leaves turning a brown rust-color and barren of coffee cherries. An infected coffee plant can still produce healthy beans while infected but at a reduced rate of anywhere from 15 to 70%3. For those of you who drink only Strictly High Grown beans (beans grown 4,000+ feet above sea level), the threat of rust is less severe as evening temperatures are still cool enough to prevent the rust from setting in.

Scientists and pathologists have been working to create rust-resistant strands and hybrids of the two most common, must susceptible arabicas, typical and bourbon — and some have been successful in creating a resistant, unique tasting bean. Hopefully, in time, these great minds will be able to turn their study of these beans’ resistance into knowledge that can protect the typica and bourbon from developing rust. Until then, we need to help farmers earn a fair price for their coffee so they can best care for their plants … and pray for cooler weather.


1Devastating Coffee Rust Hits 70% of Central America’s Arabica Plants

2Coffee slump reaps bitter harvest for Central American migrants

Here’s How Climate Change Hurts Coffee

Global Warming Is Helping to Wipe Out Coffee in the Wild

High extinction risk for wild coffee species and implications for coffee sector sustainability

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