The mention of the fungus with the botanical name Hemileia Vastatrix makes shoulders slump. Roya, coffee rust, is one of the worst and most feared fungal diseases on a coffee farm, whose outbreak has devastating consequences. It is responsible for millions of dollars in damages annually, and can even destroy entire harvests. The fatal thing about it: Coffee rust can be spread by wind and by humans. But let's take it one step at a time.
What is Coffee Rust?
Coffee rust, or "la roya" in Spanish or "coffee leaf rust" in English, is caused by the fungus Hemileia Vastatrix and is recognizable by orange pustules on the underside of a coffee plant's leaves. If a leaf only has a few of these round, rust-colored spots, it can continue to function more or less normally. However, if the environment promotes the development of Hemileia Vastatrix, it becomes difficult for the leaves to supply the plant with the necessary nutrients. Severely affected leaves subsequently die off.
While the fungus only attacks the coffee leaves, it damages the entire plant. Due to the lack of leaves, the coffee plant can only perform photosynthesis to a limited extent, meaning that in the year of infestation, due to a lack of nutrients, it can produce up to 50% fewer flowers and, consequently, fewer coffee cherries.
A distinction is made between primary and secondary loss.
Primary loss refers to the crop loss that occurs in the year of the first infestation. The defoliated coffee bush can no longer supply the plant with sufficient nutrients; the branches and cherries cannot develop properly.
In the following year, we speak of secondary loss, which can be even more dramatic. After an outbreak in the year of the first infestation, it may seem as if the coffee plants can recover – because they can produce leaves again in the next season. But damaged or dried, and thus dead, branches can no longer produce cherries. Studies in Central America have shown that primary loss can be up to 26%. For secondary loss, crop losses of up to 36% are even reported.
Coffee rust thus disrupts the delicate balance of nutrient supply.
Hemileia Vastatrix makes entire coffee-growing regions appear like skeletal landscapes and destroys the livelihoods of millions of coffee workers. As if the tragic extent of a coffee rust outbreak weren't enough, the fungus also spreads with ease around the world.
In the 2012/13 and 2013/14 harvest seasons, the worst outbreak to date, also known as “The Big Rust,” global losses rose to $600 million. Or to put it another way: over 300,000 people lost their jobs due to insufficient harvests.
How does coffee rust spread?
The basic conditions for Roya can be explained using a triangle. For the optimal conditions for the development of the fungus to be created, three elements are needed:
- The right environment. Temperatures of an optimal 21-25°C favor the spread of coffee rust, but it also copes brilliantly with temperatures from 15° to 28°C. If a hot and humid phase follows a rainy period, the conditions are perfectly met. Coffee rust needs water droplets on the leaves to germinate. So, if it is hot and dry, that is not a good environment for the development of Hemileia Vastatrix.
- The host. Coffea Arabica in particular is the desired host for the fungus. Coffea Canephora as well as Coffea Liberica and some varieties of Coffea Arabica are currently still resistant to coffee rust.
- The pathogen. If the environment is suitable and the host is present, a pathogen is still needed. If coffee rust is present in the region, the triangle is complete.
If coffee rust is present in a region, it spreads incredibly quickly. The most common method of dissemination is wind, which can carry spores for many kilometers. However, it is also spread by birds and insects, as well as by travelers on ships, trains, and even airplanes. At the beginning of the spread of Hemileia Vastatrix, the spores were carried by workers on their bodies and clothes, thus spreading from coffee farm to coffee farm.
On a single centimeter of an infected leaf, up to 120,000 - 150,000 spores can be found - an almost unimaginable number.
A reinforcing factor for the spread of coffee rust is also the very low genetic diversity in Coffea Arabica. Most Arabica varieties trace back to the genes of Tipica or Bourbon, which also means that they are all susceptible to the same diseases and fungi.
Hemileia Vastatrix has the ability to constantly adapt to new environments, comparable to human flu viruses, and to mutate repeatedly. Many of the varieties that were resistant up to 10 years ago are now susceptible to the existence-threatening fungus. Higher temperatures, increased rainfall, extreme winds, and increased human mobility are some of the factors that have contributed to this.
Coffee Rust. The History. The World Map.
The coffee world watched in panic as every corner of the Indian Ocean basin was affected by coffee rust in the 1950s. Hemileia Vastatrix continued its devastating conquest to West Africa and finally landed in the extensive coffee farms of Latin America in the 1970s. By 1990, it had spread to every major coffee region. However, it seemed that coffee rust was under control with adequate care and resistant varieties, which many farmers began to plant – coffee rust was, so to speak, a controllable inconvenience.
Hemileia Vastatrix was already present in the primeval forests of Ethiopia before 1870, the place considered by many to be the cradle of the coffee plant. At that time, hundreds of Coffea species and varieties existed, as well as many diseases and fungi. However, in harmony with nature and the handling and structure of coffee production at the time, an infestation of a variety with the destructive fungus or another disease had no significant impact on the ecosystem and prevented a potential outbreak.
High biodiversity can stop coffee rust. In monocultures, however, it spreads rapidly.
From the tropical hot and humid weather of Ethiopia, coffee was brought to Yemen by the Ottomans and cultivated there on a large scale for the first time. Whether they took coffee plants and thus coffee rust, or only seeds, is not precisely known. It is very possible that coffee rust never reached Yemen, as Hemileia Vastatrix adheres to coffee leaves and is not spread via seeds. In any case, the weather in Yemen was hot and dry, providing no good basis for the development of coffee rust and other diseases that cannot survive in this climate. The climate in Yemen was, so to speak, a natural deterrent to a coffee rust outbreak, and so the devastating fungus remained undetected.
From Yemen, Coffea Arabica was spread around the world by the colonial powers of France, Great Britain, and Holland. Thus, the dormant monster was given new fertile ground by favorable weather conditions. The Dutch brought coffee from Yemen to India and from there to Ceylon, present-day Sri Lanka, around 1800. Soon after, the Dutch were driven out by the British, who immediately planted extensive coffee fields to earn a great deal of money.
Ceylon - a ticking time bomb
Coffee rust was first documented in 1861 in Sri Lanka (formerly Ceylon), where it thrived due to warm temperatures and extensive rainfall, destroying the entire coffee cultivation – by the end of 1880, most farmers had switched from growing coffee to tea (which also explains why Sri Lanka is a major tea nation today).
The large-scale coffee farms were all attacked by coffee rust. Billions of fungal spores rose into the air and were spread by air currents, by people, by ship transport, by birds and insects, and especially by wind to large parts of the world. By the 1950s, coffee rust had arrived in the entire Indian Ocean basin – except in Yemen. Coffee rust contributed to the (temporary) decline of coffee production in Asia and the Pacific. While these regions accounted for a third of total production at the beginning of the 19th century, 100 years later it was only 5%.
From the mid-1950s to the mid-1980s, the epidemic broke out in West Africa and was first discovered on a farm in Bahia, Brazil, in 1970. From there, it migrated further and arrived in Central America in the 1970s. Discovered in Nicaragua in 1976, Hemileia Vastatrix had reached almost every small corner of Central America by the 1990s.
The 3 Phases of Coffee Rust Outbreak
The history of coffee rust is historically divided into three phases.
The first phase, the colonial phase, lasted from 1869 to approx. 1945 and involved the first major coffee rust outbreak in the Eastern Hemisphere. In this phase, the spread of the fungus Hemileia Vastatrix was driven by the mobility of colonial powers and their exchange of slaves for harvest labor.
The second phase, the developmentalist phase, describes the period from about 1950-1990, characterized by World War II and the Cold War. Global coffee trade was heavily regulated by the International Coffee Agreement (IAC) at this time. To keep prices relatively high and stable, the IAC set export regulations for each country. States played a larger role in marketing national coffee than they had in the colonial phase. For example, they supported farmers with technical and financial resources and promoted social and political stability through various development projects.
Global distribution of the coffee rust, 1952. This map also reflects the global distribution of Arabica and Robusta coffee at the time. Most countries east of the line produced Robusta, while those west of the line produced Arabica. Coffee Areas of the World in Relation to Rust Disease. 1952. Foreign Agriculture 16:160.
Published in: Stuart McCook; John Vandermeer; Phytopathology® 2015, 105, 1164-1173.
Copyright © 2015 The American Phytopathological Society • DOI: 10.1094/PHYTO-04-15-0085-RVW
The third phase, also known as the neoliberal phase, describes the period from the end of the 1980s to today. A devastating series beginning in Colombia is known as The Big Rust, which reached its negative peak in the 2012/13 and 2013/14 harvest seasons in Central America.
In 2008, Colombia produced 31% less coffee than the previous year. The epidemic continued to spread northward, through Central America to Mexico, then moved southward again, finally reaching Peru and Ecuador in 2013/2014. The International Coffee Organization estimates that coffee production in Central America cost more than $616 million in the 2012/13 and 2013/14 harvest years.
Unlike previous outbreaks in recent decades, the Big Rust was not triggered by a carrier brought into an area where there had been no coffee rust before. Rather, it was driven by extreme weather conditions, which had favored the development of the fungus.
The “Big Rust” in Latin America since 2008.
Published in: Stuart McCook; John Vandermeer; Phytopathology® 2015, 105, 1164-1173.
Copyright © 2015 The American Phytopathological Society • DOI: 10.1094/PHYTO-04-15-0085-RVW
Conclusion on Coffee Rust
Hemileia Vastatrix constantly adapts to new conditions.
The ecosystem and the economy are constantly changing, and so is coffee rust, which mutates continuously like flu viruses. This means that coexistence with Hemileia Vastatrix is always a snapshot and can change at any time. For example, it is much hotter in the upper regions today than it was just a few years ago. Our partners from Finca El Arbol used to have a maximum daily temperature of about 25°C at Easter, the hottest time of the year in Nicaragua, but today temperatures rise to 35°C or higher.
Unstable stock market - catalyst for Roya
Added to this are the challenges of the stock market, which keeps prices unstable and makes long-term future planning impossible. If prices are too low and the coffee farmer cannot cover costs, let alone invest in renewing coffee plants, maintaining the coffee farm, or combating Hemileia Vastatrix or diseases, they must abandon their farm. The land becomes wild, and coffee rust spreads unchecked.
Roya made coffee production more expensive
The control of Hemileia Vastatrix has significantly increased the cost of coffee production. At low prices, farmers cannot afford to control it and have to abandon their farms, leave rural life, and build a new life elsewhere.
Roya shaped the coffee world as it is today
While coffee rust has only marginally reduced the global supply of coffee, it has shaped global trade in other ways. After 1900, the Dutch invested in the development of the resistant species Coffea Canephora, which soon revolutionized the global coffee scene and today accounts for about 40% of coffee production. The plant, originally developed as an answer to coffee rust, transformed and shaped the structure of global coffee production and consumption in the 20th century. But more on that another time.
Further Reading
https://www.youtube.com/watch?v=gnPChFLHWA4
https://apsjournals.apsnet.org/doi/10.1094/PHYTO-04-15-0085-RVW#fig1
Stuart McCook, 2019, Coffee is not forever
