Coffee Leaf Rust

Yellow-orange, powdery pustules develop mainly on the underside of leaves, with corresponding pale yellow spots visible on the upper surface. Heavily infected leaves drop prematurely, progressively thinning the canopy and reducing the tree's capacity to fill developing cherries.

Spores are dispersed mainly by wind and rain splash and germinate in the presence of free moisture on the leaf surface. Hemileia vastatrix is an obligate parasite requiring living coffee tissue, and repeated infection cycles can build up over a growing season under warm, humid conditions.

• Free moisture on leaves, from rain or dew, is needed for spore germination and infection
• Wind carries spores between plants and can move inoculum across a plantation and beyond
• Numerous distinct races of the pathogen exist, affecting which cultivars remain resistant over time

Coffee is the host of Hemileia vastatrix. Arabica coffee is generally more susceptible than robusta coffee, and susceptibility varies further among individual cultivars and with the pathogen races present locally.

• Warm temperatures combined with humidity and leaf wetness from rain or dew
• Dense, heavily shaded, or poorly ventilated plantings that retain leaf moisture
• Susceptible cultivars
• Plant stress from heavy bearing loads or inadequate nutrition, which can reduce resilience

Because coffee leaf rust depends on leaf wetness and can build up over a season, prevention combines cultivar choice, canopy and shade management, and maintaining tree vigour through balanced nutrition.

• Plant rust-resistant cultivars where suited to the region and market
• Manage shade levels and plant density to improve airflow and reduce leaf wetness duration
• Maintain balanced plant nutrition to support tree vigour and resilience
• Monitor and prune to remove severely affected leaves and improve canopy conditions