National Geographic News
Guatemalan coffee picker Rosa Diaz works her way around coffee leaves infected with a plague called roya (leaf rust/rouille orangée).

In Guatemala and throughout Central America, coffee infected with a fungus known as rust has reduced yields. Along the Equator where coffee grows best, the problem of yield is widely attributed to more extreme rainfall.


Dan Stone

National Geographic

Published May 31, 2014

For nearly six years, a fungus that's commonly known as rust has killed so many coffee trees in Central America that scientists have speculated the region could lose up to 40 percent of its coffee crop.

Now, as researchers scurry to maintain the global coffee supply, there are signs that climate change and wild weather could make the problem even worse.

"We just keep getting report after report at our partner institutions in those countries—these are growers, buyers, importers, and roasters," says Tim Schilling, director of World Coffee Research at Texas A&M University, describing the problem in places like Panama and El Salvador.

Known as roya in Spanish, the rust fungus has also engulfed parts of Guatemala, Nicaragua, Mexico, Costa Rica, and Honduras.

The ultimate culprit: a phenomenon that scientists call climate variation, which sees weather patterns changing dramatically from year to year. More rain in recent years has meant more rust, which blankets the leaves of coffee trees, cuts off sunlight, and restricts photosynthesis until a coffee tree keels over and dies. (Related: "Coffee: Beyond the Buzz.")

Guatemalan coffee picker Rosa Diaz works her way around coffee leaves infected with a plague called roy.
The majority of South and Central America’s coffee is grown by small-scale farmers. Rust has created widespread concern about the future of coffee prices and the economic impact of thousands of farmers becoming unemployed.

Last year, a United Nations panel of climate scientists found that downpours related to El Niño and La Niña weather events—periodic changes in the Pacific Ocean's temperature that influence rainfall near the Equator—will intensify this century, leading to even more precipitation.

The problem has attracted attention from Central American governments, which see depressed coffee futures as a threat to their economies. Some coffee producers, meanwhile, have accepted help from development organizations, which fear that too many unemployed farmers could lead to widespread poverty and fuel other problems, like the drug trade.

The United States—which consumes more coffee than any other country but produces close to zero—recently announced a five-million-dollar grant to Texas A&M's coffee research program to help combat rust.

Photo of Luis Manuel Antonio (left) preparing to head home with his father, Luis Antonio (middle), and his mother, Teresa Antonio, in Loma Linda, a small coffee producing community in western Guatemala.
Guatemalan coffee grower Luis Manuel Antonio (far left) has seen coffee rust ravage his small farm. The diminishing yields have caused stress and anxiety for him and his wife. Other areas have seen rises in child malnutrition as a result of declining income.

Coffee Climate

Because coffee is so weather dependent, it's an especially volatile crop. Too much water fuels a debilitating fungus. Too little sucks the tree dry.

Add in the variations of harsher winters, more rainfall in some areas, and none at all in others, and the world's third most popular drink (behind water and tea) is becoming much harder to produce.

"We used to think that seasons were not that important; now we see that they're incredibly important," says Alvaro Gaitan, head of plant pathology at Colombia's National Coffee Research Center.

The problem of rust is not new in Central America. The fungus has appeared in multiple waves since the 1970s but mutates each time, complicating researchers' efforts to combat it.

When rust struck Colombia in 2008, it spread from farm to farm, cutting the country's coffee output from 12 million bags to 7 million in a single year. The country's economy sputtered. Some farmers—many with less than a single hectare of land—had no crop at all.

Earlier this year, Brazil faced the opposite problem of Central America's: an unprecedented drought caused farmers to lose nearly one-fifth of the country's usual 55 million bags of coffee.

Coffee prices rose worldwide from $1.20 per pound to nearly $2.20. Most large coffee chains, including Starbucks, absorbed the higher cost rather than pass it on to customers.

But rain arrived in March, and Brazil's coffee industry is expected to bounce back, with around 50 million bags anticipated next year. Even that may not be large enough to keep prices stable.

Coffee pickers wind through the vast Zaragoza coffee estate in Nicaragua, transporting their daily harvest to a central measuring station.
Nicaraguan coffee pickers, who generally travel from farm to farm during the harvest season, have seen their work dry up as rust affects more plants. By some estimates, the fungus has led to drops of as much as 40 percent of annual yields in parts of Central America.

Genetically Modified Coffee?

Combating rust has proven more elusive than Brazilian rain.

The fungus continues to mutate, appearing in Guatemala and Nicaragua in different strains than the one detected in Colombia. Most farmers douse plants in expensive fungicides, but there's little research on whether chemical treatments work on new strains of rust.

"We don't have the products or the tools to fight this disease," Carlos Torrebiarte, a Guatemalan coffee farmer, told an interviewer in 2012. His yield was expected to fall by 30 percent.

The solution, agriculture experts say, is to engineer new plants designed to withstand the attack of the fungus.

"The main strategy is to use genetics," says coffee researcher Schilling, who is overseeing some of the science funded by the multimillion dollar grant, to be administered by the U.S. Agency for International Development.

Members of Guatemala's Manos Campesinos coffee producers' cooperative bag every bean they can find on their drying patio in Loma Linda, a small coffee growing village in Western Guatemala where small scale producers have seen their farms ravaged by coffee leaf rust in recent years, pushing some farmers into financial ruin.
In light of the rust epidemic, coffee farmers in western Guatemala keep track of every bean they produce to make sure that none are lost in the process of harvesting, drying, and bagging the coffee.

Schilling's team is working to create rust-resistant seeds with hopes of replacing as many plants as possible in Central America that are susceptible to the fungus.

The biggest question may be whether farmers can be persuaded to let foreign scientists with genetically modified seeds swoop in to replant coffee fields.

Governments will likely need to subsidize the seeds. And nonprofits will have to ensure that those seeds are planted correctly. Many experts wonder if the process, unfolding over many seasons—some years without any yield at all—will drive farmers to try to find other work.

Luis Fernando Samper, a coffee marketer with the National Federation of Coffee Growers in Colombia, is confident that rust can be defeated over the next decade by replacing sick trees. For a fickle crop in a fickle climate, however, the challenges are likely to keep coming.

Follow Dan Stone on Twitter.

Monika Firl
Monika Firl

Interesting article.... but unfortunately the "solutions" suggested by Mr Shilling are the same failed strategies that the coffee industry has implemented every time leaf rust attacks a region (this disease have ravaged coffee whenever the combination of high temperatures, humidity and depleted soils allows - since the mid-1800s). . 

What is NOT being reported are the amazing, successful experiences that intensive organic practices have demonstrated in roya-infested regions of Central America. It is not coincidental that the dearth of attention follows where Monsanto (or Texas A&M) have no opportunities to patent, sell or otherwise see big funding channeled into their accounts!

David Zavala Gutierrez
David Zavala Gutierrez

This is the primarily source of people movement along the borders of Mexico and the reason is clear: America does not produce coffee (in the contiguous 48 and Alaska), so keep coffee farmers and their families where they belong, in their homelands, with better techniques and material to sustain their activities.

Skip Tindle
Skip Tindle

 Earth’s climate has changed many times. Earth has also experienced several major ice ages. The climate change brought by El Niño, which relies on winds and ocean currents, is an example of natural atmospheric changes. Some scientists say the number of sunspots has doubled in the past 100 years, making the sun brighter to us—and making it warmer here on Earth. We are just pretty much along for the ride.

tao observer
tao observer

Great - if the answer is genetically modified plants, Monsanto will be able to expand its domain and control.  Hopefully there is another choice besides dousing plants with pesticides and genetically modified crops. I would rather switch to another morning beverage than drink either product.  Good thing I like Sumatran beans.

Peter Pearsall
Peter Pearsall

Looked at from the home page, the subhed of this article states that coffee is "the world's second favorite beverage..." but in the article it's "the world's third most popular drink..." Is this a distinction between the words "beverage" and "drink" , or just a slight editorial oversight?

susan wang
susan wang

Extreme weather events are becoming more frequent.  What can we do?

Janet Brighenti
Janet Brighenti

The rust fungus problem is growing in Hawaii as well. To control it in my (admittedly small) 1 acre yard I spray my citrus trees and vegetable garden with a solution of water, dish soap, and neem oil, sometimes adding melaleuca alternifolia (tea tree) oil. So far, it's getting rid of the rust fungus for me.

C. Dufour
C. Dufour

Okay global warming:

you can take polar bears

you can take the ice caps

heck you can even rise the oceans


Norma Okun
Norma Okun

this shows you cannot put all your eggs in one basket. My hope is that the farmers be blessed with new research that can wipe out the fungus.

Gerard Van der Leun
Gerard Van der Leun

Global Warming you powerful god! Is there anything you can't do?!!!!  So impressive, so deep, so full of the aroma of all that comes out of a bull's fundament! Inhale and chow down oh lucky Nat Geo scribblers!

Mind Bird
Mind Bird

It would be nice if they said whether it was shade-grown (traditional, and good for songbirds) or one of the new full-sun kinds, or both, that were affected.

Monika Firl
Monika Firl

@tao observer there are beautiful, organic coffees from most growing regions around the world that have no Monsanto fingerprints -- in fact are a delicious way to combat the Monsanto empire! :-D

Liam L.
Liam L.

@Peter Pearsall There is a high chance that it is just an editorial oversight, considering how mutually we say "beverage" and "drink" . 

However, in this case, I believe the author is well aware of the difference between "beverage" and "drink". As far as I know, "beverage" applies for hot drinkables while "drink" is cool drinkables :/ 

I might be wrong, so do not take my words for it.

tao observer
tao observer

@Mind Bird

Found at this link.  Sounds like shade grown is less susceptible if this is accurate.

"One of the key cultural management decisions is whether to produce the coffee in full sun or with some degree of shade (Figure 11). This often is more a sociopolitical decision than an agronomic one. Some say that rust is easier to control on properly spaced plants in full sun, since they dry faster and, therefore, have shorter periods of leaf wetness. (They also are easier to spray with fungicides.) Others argue that shade-grown coffee has less rust because the closed canopy of shade trees prevents dew formation on the coffee leaves and therefore reduces infection. However, dew usually does not remain long enough to support infection. It is more likely that shade reduces the susceptibility of the plant to rust because yields are reduced; production of a heavy crop depletes the tree of nutrients and makes it more susceptible to infection. In general, sun-grown coffee is produced on large, well-capitalized farms that can afford to control the rust with fungicides, the cost of which is offset by the higher yields. The small, "low-tech" producers tend to favor shade-grown coffee, which, despite its lower yields, requires less external input in the form of pesticides and fertilizers. They often grow a variety of shade species that provide fruit, fire wood, and timber to meet their own needs. Some of the shade trees host nitrogen fixers that reduce the need for applied nitrogen fertilizers. The multi-layered canopy intercepts and slows the falling rain, reducing run-off and the consequent soil erosion. The structural diversity provides an improved habitat for birds, mammals, reptiles, insects, and numerous other species, and these refuges scattered along the migration routes of migratory birds have an environmental impact well beyond the coffee farms themselves.

Since the susceptibility of the plant is markedly affected by its nutritional status, the depletion of nutrients by a high yield in a given season can increase the severity of rust not only in that season but in subsequent years as well, unless appropriate adjustments in nutrients are made. Fertilization with nitrogen (N) and phosphorus (P) tends to reduce the susceptibility to rust, but excessive potassium (K) increases susceptibility. In general, application of micronutrients reduces susceptibility. Since their effects can be felt over several seasons, such adjustments must be made carefully."


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