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were too hot during the day and, more importantly, too cold at night. The same climatic variation that produces great sugars and acidity in high-altitude coffee kept the rust at bay. Around 2008, however, things began to change. "We started getting reports of rust at 1,700 to 1,800 meters," says Dr. Gaitán. Additionally, as coffee prices began to drop (and petroleum pric- es shot up, which meant higher costs for fertilizer), famers had fewer incentives to take care of their fields. Pruning, fertilizing, and maintaining best practices were more expensive and the revenue was less, so farmers weren't spending as much money or as much time working their coffee fields. Cenicafé has hundreds of weather stations scattered over the entire country, and has been recording tem- peratures, precipitation, daylight, and other environmental factors for decades now, giving the research- ers reams of data and a historical timeline aganist which to measure change. And that data was clear: Many areas had higher measured temperatures but lower thermal amplitude (the difference between high and low temperatures during a daily cycle) plus higher than aver- age rainfall. "We had more rain and clouds, with less sunlight during the day (where clouds work as an umbrella in reverse, blocking the sun), and at night the clouds are like a blanket, keeping temperatures warmer," says Dr. Gaitán. "Coffee rust doesn't like sunlight," he adds, but the clouds were keeping that sunlight from reaching the plants. Add it all up, and, "It was a perfect storm for rust," he says. The same factors have been at work in Central America in the last year, helping the disease rav- age many farms. In fact, because rust began showing up in places where it had never been a problem before, some people believed it was new strain of the disease. But Dr. Carlos Rivillas, another plant-dis- ease pathologist at Cenicafé, says a genetic analysis of the rust deter- mined that the strain was the same as before, which is known as Race II. It was moving into new territory then not because it had changed, but because the territory had. Change is really the story of rust and coffee. The environment changes, and that makes new coffees accessible to the disease. Change the coffee plant (by developing a new hybrid, for example), and you can keep the disease at bay—temporarily. Evolution continues, and rust changes along with it, finding new ways to attack the coffee plant. A plant that is resistant today, therefore, may not be resistant tomorrow. Picture a key slipping into a lock. The rust fungus is the key, and the plant's defenses are the lock. If the plant's resistance is uncomplicated, for example, it won't take long for a genetic mutation in rust to unlock the plant. If the plant's resistance is more robust, then the key necessary to open it will need to be 81 www.baristamagazine.com B o o k 5 5 - 8 8 . i n d d 8 1 Book 55-88.indd 81 3 / 1 9 / 1 4 1 0 : 0 9 P M 3/19/14 10:09 PM