Fungus Threatens Crop Production At Mexican, Central American Coffee Plantations

Chuck Bednar for redOrbit.com – Your Universe Online
We hope you were able to take advantage of one of the many free National Coffee Day giveaways on Monday, because ecologists at the University of Michigan report that a fungus has been sweeping across plantations in Mexico and Central America, limiting coffee production and forcing price increases in the process.
According to the National Science Foundation’s (NSF) Division of Environmental Biology, which is funding Ivette Perfecto’s investigation into the matter, several countries – including Guatemala, Honduras and Costa Rica – have already been forced to declare national emergencies as a result of a fungus known as coffee rust.
In fact, the current outbreak of coffee rust (which is also known as Hemileia vastatrix) is said to be the worst since the pathogen first arrived in the region some four decades ago. Guatemalan farmers believe coffee production there could drop by 40 percent, and given that Central America supplies up to 15 percent of the world’s coffee supply, the ongoing blight could ultimately make a cup of your favorite espresso or cappuccino much more expensive.
“It’s hard to overstate the social and economic importance of coffee – it literally touches our lives every day,” NSF Division of Environmental Biology program director Doug Levey said in a statement Monday. The agency added that coffee is “one of the most traded commodities in the world,” and that it “provides support for millions of small farmers and is an important economic engine in tropical countries,” including 20 in Latin America.
The origins of this fungus date back 150 years ago, when coffee rust first appeared in the Lake Victoria region of Africa, the NSF said. It soon spread throughout the coffee-growing areas of that continent and into Southeastern Asia. By 1970, it had made it to Brazil, and it has since spread to every coffee-producing country on Earth because the fungal spores are dislodged from coffee leaves by rain and then carried elsewhere by the wind.
“It became so devastating in Sri Lanka, southern India and Java that coffee agriculture had to be abandoned,” Perfecto said. She and fellow UM ecologist John Vandermeer have conducted more than a decade’s worth of research at an organic coffee plantation in Chiapas, Mexico. More than 60 percent of the plants at their site have been defoliated due to the rust, which affects the plants by halting photosynthesis.
Part of the problem, she and fellow UM ecologist John Vandermeer explain, is the growing trend to abandon traditional growing techniques in which coffee plants are placed beneath tall shade trees. Farmers are reducing the number of shade trees on their plantations, they noted, and in order to increase production, they’ve started producing sun coffee (coffee in which the tree canopy is removed or thinned).
“Coffee farmers are also relying more heavily on pesticides and fungicides to manage threats to their plants,” Perfecto said, noting that the increased reliance of these techniques has led to concern about how to exactly combat the threat of coffee rust. Levey said that the best control method is most likely “promoting the ecological balance between the fungus that causes the disease and the organisms that naturally rein it in.”
Furthermore, the Michigan researchers note that the lack of shade may have caused another type of fungus, known as white halo fungus (Lecanicillium lecanii), to die out. White halo fungus helps keep coffee rust at bay, and without it the fungus had started to spread like wildfire. The two fungi are part of a complex coffee plant ecosystem that also includes the ant Azteca instabilis and another coffee pest, green coffee scale (Coccus viridis), the authors said.
The four species “are embedded in a system of ecological interactions,” said Perfecto. The ants are reliant upon green coffee scale, which is in turn consumed by the white halo fungus that attacks and destroys coffee rust. All three are required on a farm to combat Hemileia vastatrix, and this works best under a shady canopy, she added.
“This research reveals a surprisingly natural ecosystem nested within a major agricultural crop,” Levey said. “It demonstrates that an ‘agroecosystem’ can be used as a model to study the natural control of plant diseases that threaten crop production.”
“But this mutual benefit depends on how farms are managed,” the NSF added. “In the case of coffee rust, fewer canopy trees cut down would be a major step forward, say Perfecto and Vandermeer. Bring back the shade… and the Azteca ants, green coffee scale and the… white halo fungus… will reappear.”
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