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Environment & Science

'Coffee rust' fungus brews up trouble in Central America

A leaf showing signs of Coffee Rust fungus.
A leaf showing signs of Coffee Rust fungus.
Howard F. Schwartz/Colorado State University

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Coffee growers in Central America are facing a big crisis due to the increasing prevalence of coffee rust. No, it's not what happens when you forget to wash out your coffee pot, it's a devastating fungus that could have lasting effects on the coffee crop, and on the price of coffee at home.

"It's a disease caused by a fungal rust that enters into the leaf and causes yellow spots all over the leaf and it interferes with the normal functioning of the leaf," said Professor John Vandermeer, an ecologist who studies coffee rust at the University of Michigan, Ann Arbor. "When the leaf drops off the plant, that cuts down on all the photosynthesis that the plant is going to do, pretty dramatically, actually."

The fungus is devastating crops in Central America, which has become one of the most important growing regions in the world. It's the worst outbreak in more than 40 years and it's estimated that this year's crop could be cut by a third or more.

The British colonies in Southern India, Ceylon (now Sri Lanka), Sumatra and Java were once top coffee growing regions, but their crops were decimated by coffee rust. According to an article by the American Phytopathological Society, in 1870, the British were exporing 100 million pounds of coffee from Ceylon, but by 1889, that number dropped to 5 million. Within 20 years, coffee production had ceased and the colonists shifted their focus to growing and harvesting tea instead. 

"Many historians believe that that's one of the reasons it became so common in Central America and Mexico and North and South America right about that same time," said Vandermeer. "We think that what happened in those areas was gradually the system was changing to be more intensified to the point where the disease reached a tipping point, became an epidemic and remained an epidemic."

Vandermeer and his colleagues posit that one of the issues that may be contributing to the outbreak is the shift from the traditional way of growing coffee, under the shade of the forest, to a more modern way of growing it in full sun. The question now is whether or not this epidemic will continue in the years ahead. If that is the case, coffee lovers can expect the cost of their favorite pick-me-up to increase greatly.

"Our estimates are that the effects could be very large, but the coffee could recuperate relatively rapidly. Next year the yields are going to be very reduced, so I can imagine that that's going to have quite an effect on coffee prices in general world wide," said Vandermeer. "The real question in my mind is whether this disease is going to be a continual problem like this not just this year, but in the foreseeable future."