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Coffee varieties of mesoamerica and the caribbean

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Shade, fertilization, and coffee leaf rust

How two key factors influence rust
shaded coffee


The coffee leaf rust epidemic in Central America that began in 2012 took the entire industry by surprise. There were many unusual factors to the epidemic that left farmers, agronomists, and researchers scrambling for answers. 

Typically, the amount of fruit on a coffee plant can explain 50% of the coffee rust variability (when a plant produces a lot of fruits, it stresses the plant and it is more susceptible to rust). However, during the 2012-13 epidemic, even young plants with no fruit or immature plants in nurseries were severely affected. Similarly, contrary to expectations, coffee rust did not decrease with increasing altitude. In Guatemala, for example, severity of rust attack was equally high in farms ranging from as low as 400 to 1400 m. (This situation is consistent with increased temperatures at higher altitudes.)

Not all farmers were affected equally. Two factors in particular seemed to have an effect on the severity of rust attacks, even on farms right next door to one another: fertilization and shade. Farmers across the region who applied appropriate fertilizers were less affected by rust. This makes sense—a well-fed plant is likely to be more resilient to stressors like disease. But the effects (both direct and indirect) of plant nutrition on both the severity of rust infection and the capacity of the coffee plant to recover from rust damage, are not well understood.

In addition, shade is also known to affect coffee rust development, though shade can have antagonistic effects. During the recent epidemic, rust infestation was similar in plots under shade or at full sun exposure (in spite of the lower fruit load normally reached under shade). However, the amount of defoliation and dead branches was higher at full sun than under shade. Coffee plants at full sun were particularly stressed (low rainfall and high temperatures) during the epidemic in 2012.


A combination of shade and fertilization seemed to be the basis of successful management of coffee rust epidemic that began during 2012-13. But defining the specific approaches that worked, and understanding why they worked, is critical for providing accurate guidance to coffee producers in the future.

For example, different heights of shade and leaf shapes could affect how water drips down to coffee plants underneath, either helping or hindering the spread of leaf rust spores. By studying different kinds of shade, we can identify the shade attributes that are most relevant for fighting coffee rust.

WCR is studying these complex interactions—between shade, fertilization and rust—on 48 plots in Acatenango, Guatemala, a region severely hit by coffee rust in 2011-12 and at the International Tropical Research Center (CATIE) in Costa Rica. The plots differ by type of shade (Gravilea, Inga, and diversified), the intensity of cropping practices and levels of fertilization (high, low), and by altitude (lower: 1250-1500 m, higher: 1500-1750 m).


A systemic approach to fighting disease—involving environmental, agronomic, and chemical controls—will almost always be more effective and more sustainable than single, silver-bullet solutions. The results of this research will assist in decreasing the substantial confusion caused by the leaf rust epidemic in Central America and lead to improved training for farmers and help refine best practices for managing rust.

Project Updates

  • Rust lesions
    Rust lesions

    Rust lesions on a leaf. Photo credit: Jacques Avelino


    Researchers and students from CIRAD and CATIE, with funding from World Coffee Research, spent nearly a year taking exhaustive measurements of the movement of rust spores in a coffee agroforestry research site at CATIE in Turrialba, Costa Rica. Their findings were published in Crop Protection.

    Researchers have known for years that shade can have both positive and negative effects on coffee leaf rust—but this team wanted to understand what was behind some of those different impacts, so that better guidance can be provided to coffee farmers interested in agroforestry—an increasingly important approach for managing rising temperatu...

    Read the Whole Story
  • Roya

    What is better for the coffee plant: to spray against rust, or to give the plant better nutrition to allow it to grow stronger and as a result fight rust?

    Read the Whole Story
  • shade and rust

    Many existing approaches for controlling coffee leaf rust are one-sided: Use rust-resistant varieties, or spray with as much fungicide as you can afford. But it is increasingly evident that we need to open new fronts in the fight against coffee leaf rust.

    Read the Whole Story
  • Location: Guatemala, Costa Rica
  • Leaders: Jacques Avelino, CIRAD
  • Partners: CATIE
  • Timeline: 2015-2017 (COMPLETE)