Coffee leaf rust (Hemileia vastatrix), commonly called roya in Spanish-speaking producing countries, is a fungal disease that attacks coffee plants. It has caused major outbreaks for over 150 years and is one of the most economically damaging diseases in agriculture.
What it does
The fungus infects the underside of coffee leaves, producing distinctive orange-yellow spots. As infection progresses, leaves drop prematurely. Without leaves, the plant cannot photosynthesize, the cherry yield collapses, and the plant itself can die in severe cases.
Once a plantation is infected, full recovery takes years. Trees need to be either treated repeatedly or removed and replanted with resistant varieties.
The 2012 Central American outbreak
The most devastating recent outbreak began in Central America around 2012. Within three years, rust had reduced coffee production in countries like Guatemala, Honduras, El Salvador, and Costa Rica by 30-50% in many regions. Hundreds of thousands of farm workers lost income. Several countries declared coffee emergencies.
The outbreak particularly affected the traditional Bourbon and Typica varieties that produced the region’s celebrated washed coffees. Many farms were forced to replant with disease-resistant cultivars that are less prized for cup quality.
The climate connection
Coffee rust thrives in warm, humid conditions. Higher elevations were historically protected because cooler temperatures slowed the fungus. As average temperatures rise, the rust-favorable zone is moving uphill, reaching elevations that were previously safe.
The combination of warming temperatures, irregular rainfall patterns, and increased humidity at higher altitudes has made rust outbreaks more frequent and harder to contain.
How farms fight it
Three main approaches: fungicide treatments (effective but expensive and environmentally controversial), shade management (heavier shade slows rust progression), and resistant varieties (Castillo, Marsellesa, F1 hybrids like Centroamericano). The trend has been toward resistant varieties because they reduce ongoing chemical inputs.
Why it matters to drinkers
Major rust outbreaks reduce supply and push prices up. They also push producers toward rust-resistant varieties, which are often less interesting in the cup than the traditional Typica and Bourbon they replace. The flavor profile of Central American coffee in 2026 differs measurably from 2010, partly because of variety changes driven by rust.