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Why Europeans Drink Tea
Gail L. Schumann
from the book Plant Diseases:
Their Biology and Social Impact
Coffee is a crop of the tropics surpassed only by oil in its value as a world
commodity. For centuries, it has been a significant import crop in Europe and economically
important to the European countries that ruled tropical colonies. It remains an important
crop to the independent nations created from those colonies.
Coffee became a popular drink in Europe in the 1600s when contaminated drinking water
limited people to fermented beverages or those made with boiled water, such as tea or
coffee. Coffee houses were major social centers in England in the 1650s. The Dutch were
the first major European coffee importers, transporting coffee from their colonial
plantations in Ceylon (now Sri Lanka), Java, and Sumatra.
Coffee with the berries that contain the seeds or
"beans" that are harvested and roasted.
|The small, nondeciduous tree, Coffea arabica, produces
red berries that contain the seeds or beans that are roasted and then brewed into a potent
caffeinated drink. The trees grow best in cool, humid climates but cannot survive frost
and are thus limited to tropical highlands.
|During Napoleon's time, much of the coffee-producing area was
lost by the Dutch to the English. In 1825, the British began development of their property
in Ceylon (now Sri Lanka), and every suitable piece of land was planted to coffee
plantations. By 1870, Ceylon was the world's greatest producer of coffee. Java
remains a slang term for coffee, reflecting the time when coffee production centered in
that part of the world. Today, however, 90% of the world's coffee comes from the tropical
Western Hemisphere. Sri Lanka is now known best for its tea production, and the cup of
tea, rather than coffee, has become a familiar part of England's culture. As with the
Irish potato famine, a fungus was responsible for these changes, but only because of the
agricultural practices of human beings.
The fungal parasite probably arose in southern
Ethiopia, the origin of the coffee plant itself. It is a Basidiomycete, a fungal group
containing many important plant parasites, and belongs to a subgroup known as the rusts.
The rusts are such important plant pathogens that they are discussed in detail in Chapter
10, and the complete biology of the coffee rust fungus is explained there. It is
sufficient at this point to consider the problem of a rapidly reproducing fungus capable
of infecting the foliage of the coffee tree, a nondeciduous, perennial plant that grows in
a frost-free climate.
Symptoms of coffee rust infection (Hemileia vastatrix).
single tiny rust pustule on a coffee tree leaf can produce 150,000 spores, and a single
leaf can contain hundreds of pustules. When the coffee rust fungus, Hemileia vastatrix,
reached Ceylon in 1875, nearly 400,000 acres (160,000 hectares) were covered with coffee
trees. No effective chemical fungicides were available to protect the foliage, so the
fungus was able to colonize the leaves until nearly all the trees were defoliated. The
spores produced on the leaves are quite resistant to desiccation, unlike the sporangia of P.
infestans, and are capable of long-distance movement in a viable state. They easily
moved through the acres of coffee trees, feasting on the banquet prepared by unsuspecting
plantation owners. In 1870, Ceylon was exporting 100 million pounds (45 million kilograms)
of coffee a year. By 1889, production was down to 5 million pounds (2.3 million
kilograms). In less than 20 years, many coffee plantations were destroyed, and production
had essentially ceased.
World distribution of the coffee rust fungus, with the
dates it was first discovered.
||H. Marshall Ward, a contemporary of Anton deBary, was sent to
Ceylon by the British government to save the coffee plantations. Even though he failed, he
presented the infant science of plant pathology with two important concepts that are still
fundamental to plant protection. His studies of the life cycle of the rust fungus
convinced him that the germinating spores represented a vulnerable stage for attack.
|He recommended that, to effectively protect the plant from
invasion, fungicides should be present as a protective coating on the leaves before the
spores arrived. Once infection had occurred, the hyphae inside the leaf tissue were no
longer vulnerable to the fungicide. Thus, it was important to anticipate the disease and
not to wait for symptoms to appear before spraying was initiated. Unfortunately, the
sulfur fungicides of that time were neither readily available nor very effective, and the
rust epidemic was too well established to save the coffee trees.
|Ward also warned about the dangers of monoculture. He observed that
the continuous plantings of coffee trees over the island had created a perfect environment
for a fungus epidemic. Rusts, like downy mildews, are obligate parasites and require
living host tissue for their growth and reproduction. The rapid epidemic of the coffee
rust was enhanced by the many acres of the host plant. His warnings, unfortunately, were
ignored, and most of the dead coffee trees were replaced with tea bushes. Luckily, no
fungus immediately invaded the tea crop, and newly discovered fungicides were soon
available to protect the tea from its fungal parasites.
Coffee plantations on a steep hillside in Columbia.
|In an attempt to escape the rust disease, coffee production
moved to the Western Hemisphere. Coffee had been grown in the Caribbean Islands since the
1700s, but plantings quickly spread to the tropical highlands of Brazil, Colombia, and
Central America. Today, Brazil, followed by Colombia, dominates the world coffee market.
Coffee production centers in the tropical Americas because the coffee rust was
successfully excluded by careful quarantines.
The quarantine was successful for over 100
years, but, in 1970, coffee rust was discovered in Brazil. It is not completely clear how
the fungus arrived in Brazil, but intercontinental movement of the rust spores from coffee
plantations in East Africa is a likely means. The dustlike spores could also have been
easily carried on luggage, people, plants, or airplanes that continuously move between the
continents. Eradication of infected trees has failed to eliminate the parasite, and the
fungus has slowly spread throughout the coffee-growing areas, moving into Colombia and the
countries of Central America. The spread was delayed by careful quarantines between many
of the countries, but political unrest and human travel, along with natural dispersal of
spores by wind, have allowed the fungus to circumvent the quarantines.
Billboard near the airport of Bogata, Columbia, waning
about the danger of importing the coffee rust fungus, before its introduction to South
What will be the consequences of the importation of such a dangerous pathogen? Frequent
fungicide applications will be necessary to protect the highly susceptible cultivars of C.
arabica, which produce the best quality of coffee. Chemical inputs are particularly
demanding for small growers, who now must purchase fungicides and spraying equipment.
Trees must be grown at lower densities to allow complete fungicide coverage of the
susceptible foliage. Wider spacing of trees also increases air movement between the trees.
When the foliage dries more quickly, infections are reduced since, like almost all fungal
spores, rust spores require water for germination. Chemical inputs and changes in planting
practices increase the costs of production and hence the price to consumers.
Rust-resistant cultivars of C. arabica and other species such as C. canephora
exist, but the crop is of poorer quality. Plant breeders must often struggle with the
problem of combining desirable genetic traits for crop quality with genes for resistance
in the same plant. Rust fungi are capable of producing many genetically different races,
and 32 races of H. vastatrix have been detected. It is always particularly
difficult to find durable resistance to a pathogen when the crop is a perennial growing in
a frost-free environment. The pathogen population is not reduced by winter stresses, and
replanting with new cultivars is expensive and infrequent. Resistance that is effective
against all races of the parasite remains the long-term goal. In the meantime, fungicide
applications are becoming part of the routine production practices on coffee plantations
in the Western Hemisphere.
© Copyright 1998 by The American