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Significance

Losses
Coffee rust causes premature defoliation, which reduces photosynthetic capacity and weakens the tree. Since next season's berries are borne on this season's shoots, this season's rust reduces next season's yields. Depending on weather in the current season and the yield and the level of infection the previous season, yields can vary as much as 10-fold from one season to the next. Severe infection can result in dieback of twigs and can even kill trees (Figure 13).

Figure 13

Economic impact
Coffee rust is the most economically important coffee disease in the world, and in monetary value, coffee is the most important agricultural product in international trade. Even a small reduction in coffee yields or a modest increase in production costs caused by the rust has a huge impact on the coffee producers, the support services, and even the banking systems in those countries whose economies are absolutely dependent on coffee export.

History
Coffee originated as an understory plant in the forests in the mountains of Ethiopia. Its early use was as a food, in pressed cakes, often carried on camel caravans by North African traders. Its first use as a drink was probably for medicinal purposes and in religious rituals, but its stimulating and refreshing qualities made it popular. Coffeehouses were common throughout Egypt, Arabia, and Turkey by the early 1500s, and European travelers developed a taste for this exotic brew. The Dutch saw the business potential in coffee and began to plant coffee in their colonies in Ceylon, Sumatra, and Java. "Java" remains a slang term for coffee in many places.

By the early seventeenth century, coffeehouses had sprung up in all the major cities of Europe, with the Dutch being the major coffee supplier. A taste that began with the nobility and the wealthy soon drew in the common folk as well. Coffeehouses became the places where the intelligentsia gathered to discuss philosophy, religion, and politics (Figure 14). Rulers throughout history have felt threatened by this free thinking and have moved to restrict the coffeehouses (Figure 15). Coffee had taken on a political and social importance far beyond that of just another hot drink.


Figure 14	Figure 15

By the time the Dutch ceded it to the British in the nineteenth century, Ceylon had developed into the greatest coffee-growing region in the world. The British expanded the plantations even further, stripping the island of its forests to plant coffee in every available acre. By the 1870s, Ceylon's plantations were exporting nearly 100 million pounds of coffee a year, most of it to England.

Coffee growers in Ceylon reported the appearance of a "coffee leaf disease" in 1867, later determined by Berkeley to be caused by a rust fungus. The name "vastatrix" that Berkeley gave to the species described the devastation that he anticipated from the early disease reports. (Click here for a A scanned image of the page from the November, 1869 Gardeners' Chronicle in which Rev. M.J. Berleley published the first description of Hemileia vastatrix.) Just how the fungus made its way from its native Ethiopia to Ceylon remains a mystery. At first, perhaps, the coffee growers were hoping that it would disappear as quickly as it had appeared, but by 1879, it was clear that it was not going away, and the whole country was desperate. The Ceylon government made an appeal to send someone to investigate the disease and come up with a cure.

A young botanist, Harry Marshall Ward, who had studied Anton de Bary's work on the fungi, set off on his first assignment. His observations and recommendations were fundamentally important to the then infant science of plant pathology. Ward pointed out the risks of such widespread planting of coffee without even the benefit of windbreaks to reduce the dispersal of the rust spores. A few years before Millardet and his Bordeaux mixture, Ward proposed the use of a protective fungicide (lime-sulfur) to prevent infection.

The vigor and productivity of the coffee plantations declined to the point where they were no longer economically viable. Ward had arrived too late to save the coffee, and his warnings about the dangers of monocultures went unheeded. Following a period of severe economic and social upheaval, British planters shifted to planting tea as extensively as they had coffee, and the British coffee drinkers began drinking tea. Within a few years, coffee rust had spread to India, Sumatra, and Java, and the center of coffee production shifted to the Americas, where the rust had not yet appeared. Brazil soon became the world's major coffee supplier.

Thanks to a vigilant quarantine, the Americas remained free of coffee rust until 1970, when it was discovered in the state of Bahia, Brazil. Since virtually all of America's coffee had descended from a single rust-susceptible plant, the fungus, flying on the winds, raced through the coffee- growing areas of South America and Central America in less than a decade. H. vastatrix is now found in nearly all the coffee-producing areas of the world, with the exception of Hawaii.

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