Leaf Rust Danger Grows

The coffee industry is struggling in its battle to eradicate coffee leaf rust and a concerted effort is required to protect coffee trees in many countries, according to World Coffee Research (WCR).

While fighting coffee leaf rust through genetic resistance via F1 hybrids is an effective tactic, it won’t be enough to protect farmers from significant crop losses due to pests and diseases, according to WCR.

The non-profit research group made the announcement during a presentation at the Association for Science and Information on Coffee (ASIC) conference, in Portland, Ore.

Coffee leaf rust has wreaked havoc on coffee production, particularly in Latin America, since an epidemic of the disease hit in 2012. At that time the global coffee industry united to help farmers fight the disease through the development of improved coffee varieties such as F1 hybrids, most of which are resistant to rust and other plant diseases.

WCR scientific director Dr. Christophe Montagnon explained that since that success, rust resistance in some hybrids has broken down. The latest example is Lempira developed by Honduras’ IHCAFE. Montagnon told attendees that researchers believe it is only a matter of time before rust resistance in most varieties will also decline, perhaps within 5 to 10 years.

Montagnon explained that while this development does not foretell the end of coffee production—coffee farmers have been living with coffee leaf rust for more than a century—it brings to light key elements guiding coffee’s future. He advised farmers to focus on plant health—no matter the variety of their coffee—as a major component of defense against rust.

He also cautioned that those traveling between origin countries must develop a heightened sensitivity and awareness for appropriate phytosanitary practices to prevent spreading fungi and other diseases from farm to farm or region to region, he said. Finally, the coffee industry needs to prioritize ongoing research and development. New sources of rust resistance can be found and must be discovered to foster sustainable coffee production, he said.

Fighting rust

For three years following the coffee leaf rust outbreak in 2012, the disease caused destruction in Central and South America: Many farms lost 50-80% of their production, and the epidemic forced 1.7 million people out of work and drove human migration. Once the rust outbreak hit, farmers who could afford to plant rust-resistant varieties did so, renovating areas of their farms with the new varieties. Combating diseases like rust is one action modern farmers must take to protect against the intensifying effects of climate change, which are evidenced in rising temperatures, unpredictable weather patterns, and higher rates of plant disease.

Unfortunately, no disease resistance is forever, as pathogens adapt and continue to attack coffee trees. In 2017, Honduras’ national coffee institute IHCAFE announced that Lempira, one of the varieties it had bred, was no longer resistant to coffee leaf rust. Additionally, since 2013 the Center for Research on Coffee Rust (CIFC) in Portugal has observed varieties losing their rust resistance in different countries such as Brazil and India.

In a press release distributed after the presentation WCR noted that for 30 years, rust-resistant varietals have relied on the resistant genes from timor hybrid, a natural cross between arabica and robusta coffee. According to the scientific community, the timor hybrid’s resistance is breaking down.

“Rust resistance coming from different sources of introgression—the transferring of genes from one species to another after hybridization and backcrossing—is being broken step by step,” said Montagnon. He explained that the introgressed varieties known as catimors and sarchimors that resisted rust for 30 years are no longer resisting.

“The research community shall proceed to develop new varieties with new sources of resistance but also build up comprehensive rust-control strategies that go beyond genetics alone,” Dr. Montagnon said.

World Coffee Research’s approach

A crucial part of rust-control strategies is the promotion of plant health which has been overlooked in the past, according to WCR. Just as humans are more likely to be healthy if they exercise well and eat good food, coffee is better equipped to defend against rust when it is in good health. Factors contributing to plant health include good maintenance, soil conservation, adequate plant nutrition, and adequate shading. A recent study from WCR and CIRAD showed that good fertilization can be as effective as spraying fungicide in protecting a genetically susceptible coffee from rust.

One of the main reasons for the 2012 rust crisis was farmers’ reduced maintenance of their trees due to the low prices at the farmgate.

Beyond promoting plant health, WCR writes that it is committed to collaborating in the necessary r&d work to develop new solutions.

Learn more: www.worldcoffeeresearch.org