Cafetera (Coffee Information System; Colombia)CHAPTER 1
The Devourer of Dreams
IT CAME as a surprise: a familiar nuisance suddenly turned an unfamiliar catastrophe. Over several seasons, coffee farmers from Peru to Mexico saw more and more yellow spots appear on the leaves of their trees. In previous seasons, the rust might have caused the occasional spot, but nothing serious. Now, however, leaves engulfed with lesions fell to the ground, leaving skeletal trees alive but entirely defoliated. The disease moved into highland areas that had previously escaped the disease. In February 2013, Guatemala’s Prensa libre interviewed smallholders whose farms had been devastated by the rust. “I never thought this would happen to me,” said Mauricio Méndez, whose farm had escaped the first rust outbreak in the 1980s. A smallholder named Bartolo Chavajay “could not contain his tears in the face of his rust-infested plot.” The rust had destroyed Chavajay’s entire harvest—his only source of income. Without the income, he wondered how he would feed his family. Yet another farmer, Moisés Misa, worried that the disease would harm his coffee’s quality, reducing the price he would receive from buyers and lowering his modest income. Over several seasons, similar scenarios played out in thousands of farms across the Americas. The rust, wrote the Prensa libre, devoured the hopes of farmers. Even five years later some farmers—and some countries—are still struggling to rebuild their coffee farms.1
This outbreak, now known as the Big Rust, was the latest episode in a much longer story. The coffee rust is caused by a fungus known scientifically as Hemileia vastatrix. It first entered the written record in 1869, when it was found on a remote coffee farm in Ceylon (now Sri Lanka)—then the world’s third-largest coffee producer. A little more than a decade later, the rust had driven Ceylon’s coffee growers to abandon coffee. Between 1870 and 1990, the rust slowly made its way around the world’s coffeelands, first striking Asia and the Pacific, then Africa, and finally reaching Latin America’s vast coffeelands in 1970. By 1990, it had reached virtually every major coffee-growing region in the world except Hawaii. In some places, as in Ceylon, it was a catastrophe. The rust helped drive the collapse of coffee farming in Java, an island whose name remains synonymous with coffee. As the rust made its way across the globe, however, farmers and scientists gradually learned how to adapt their farms and farming practices to the disease. Farmers were supported by a complex network of national and international organizations. By the 1990s, it seemed that the rust was just another disease. Coffee communities had adapted to the rust, much the same way that communities around the world had adapted to the influenza virus. Like the flu, the rust could be a nuisance. But properly managed, it was nothing more than that—at least in theory.
Disease, Landscape, and Society
To understand the coffee rust’s tangled history, it is helpful to understand how crop epidemics work. The coffee leaf rust is much more than the fungus alone. The fungus is present in many coffee ecosystems; in some, the coffee plants have mild infections that never develop into full-blown, disruptive epidemics. So clearly the epidemic is much more than the pathogen. We need to look beyond the pathogen alone and ask, What makes the disease a disease? To answer that, we need to consider how the coffee rust fungus interacts with the rest of the coffee ecosystem. It is helpful to consider an epidemic as a system with three major elements: the pathogen (the fungus H. vastatrix), a susceptible host (in this case the coffee plant), and the appropriate environmental conditions (rainfall, temperature, sunshine, cropping patterns, etc.). These three elements—virulent pathogen, susceptible host, and environmental conditions—can be represented as a triangle (fig 1.1).2
Epidemics are only possible if all three elements are in place. Most obviously, if the pathogen is not present, there can be no outbreak. But while the fungus is necessary for an outbreak, it is not in itself sufficient to cause one. The fungus and the susceptible coffee plant may be present in an ecosystem, but environmental conditions—say, the temperature or the farm structure—may prevent the fungus from reproducing rapidly, so there is no outbreak. In still other cases, the fungus may be present and the environmental conditions may favor the disease, but the coffee cultivar is resistant to the rust, so there is no outbreak. Furthermore, none of the three elements is absolute; different strains of the fungus can be more or less virulent, and different coffee cultivars can be more or less resistant. The environmental conditions also favor the epidemic to a greater or lesser degree. We can use the disease triangle to understand how the host, pathogen, and environment interacted in each place to produce an outbreak.
Each of these three elements is not only biological, it is also historical. Each element changes over time, the product of interactions among human and natural forces. People have, by planting thousands or even millions of susceptible plants together, unintentionally created environments that favor rust outbreaks. They have unintentionally carried spores of the rust farther and faster than the rust would have traveled on its own, infecting coffee zones that had previously been free of the disease. As farmers and scientists learned more about how the disease worked, they manipulated the host, pathogen, and environment to limit the rust. They tried to contain the pathogen through quarantines and to kill it with chemicals. They have strengthened the host by breeding rust-resistant coffee varieties. They have altered the coffee ecosystem, in places, by reducing or eliminating shade trees (fig 1.2), hoping that exposing the coffee farm to full sun would inhibit the rust.
Figure 1.1. The disease triangle, showing how the pathogen, host, and environment interact to produce a disease outbreak.
The rust attacks the leaves of the coffee plant, but it harms the whole plant. A healthy coffee tree obtains most of its nutrition through its leaves, by photosynthesis. Nutrients allow the tree to produce new branches and buds, which in due course flower and develop into the fruit. In shaded forests, the coffee plants produce few flowers, and the leaves can provide more than enough nutrients to allow the fruit to develop properly. On the farm, farmers often manipulate the plant and the landscape to encourage the plant to produce more fruit. They reduce or eliminate shade, which encourages the plant to produce more flowers and, in turn, more fruit. They can also increase crop yields by pruning and manuring the trees. But they have to be careful not to ask too much of the tree, particularly the leaves. If the nutrition required by the fruit is greater than the tree can provide, the fruit may fail to develop properly; in some cases, the branches can become starved and die. So even in disease-free ecosystems, farmers have to ensure that they do not ask the tree for more nutrients than it can deliver. Sometimes they cut it close. Heavy fruit loads can cause coffee harvests to fluctuate widely from one season to the next. A heavy crop one season can draw so many nutrients that it inhibits the growth of branches and flowers the following season, leading to a lower fruit load—a pattern commonly described as biennial bearing.3
Figure 1.2. Coffee monoculture, nineteenth century. Dense stands of coffee like this were highly productive but also highly susceptible to diseases and pests. (In Thurber, Coffee, facing p. 7)
The rust disrupts this delicate balance. When a microscopic rust spore germinates, it sends shoots into the leaf and develops into a mycelium that colonizes the leaf and feeds off the leaf tissue. It creates a circular rust-colored lesion on the leaf, which gives the disease its name. If a leaf has just a few
