Agricultural History Review, Volume 70 Part 1 (2022), p. 164

From the late nineteenth century, Coffee Leaf Rust (CLR) has posed the largest environmental threat to coffee production worldwide. CLR reduces the yield of coffee plants by disrupting the production of nutrients that allow the plants and their fruit to develop. The pathogen, a fungus called Hemileia vastatrix, is endemic in many parts of Africa, but it only becomes an effective disease when it finds a susceptible host and under specific environmental conditions. The preferred host of the fungus is Coffea arabica, which is less genetically variable and therefore more vulnerable to pests and disease than its main cousin and commercial rival, C. canephora, also known as robusta coffee. Rainfall, temperature, sunlight and cropping patterns are the main conditions influencing spore gemination and dispersal. At high altitudes, the fungus causes little damage to coffee plants, while at low altitudes, in warm and humid climates, co-existence is almost impossible. The triangular relationship between pathogen, host and environment sits at the heart of Stuart McCook’s superior study of CLR’s devastating trek across the global south after its first outbreak in 1869 and the efforts of scientists, farmers, and coffee companies to contain its impact.

Since this is in large part a study of disease control, the book mainly focuses on historical events in the climatic middle belt, ‘the space where coexistence is possible but requires effort’ (p. 6). McCook examines the global distribution of CLR chronologically, starting with a chapter on the pathogen’s natural environment in Ethiopia, giving valuable historical background to current theories of coffee agro-forestry systems. While the fungus was present in the coffee forests of southwest Ethiopia, it was contained by the conditions under which coffee was grown: the forests sheltered plants from heat, wind, and heavy rainfall, while low coffee population densities and the presence of counter-fungi further prevented rust from developing. From Ethiopia C. arabica travelled to Yemen. While the fungus possibly never joined its host across the Red Sea, it would in any event have struggled to survive in Yemen’s dry environment, as it needs droplets to germinate. During the eighteenth century, arabica moved, still free of rust, from Yemen to farming systems across Asia, the Indian Ocean, and the Caribbean. In India and Java, coffee was initially grown by smallholders as a garden or forest crop, but as the global coffee trade expanded in the nineteenth-century, colonial regimes across the global south began to favour mono-cropping and forest clearing to expand outputs, thereby increasing the vulnerability of the coffee plant.

Subsequent chapters document the first outbreak in Asia and the Pacific, the effects of CLR in colonial Africa, and its long-foreseen arrival in South and Central America in the 1970s. The chapter on Ceylon, the epicentre of the global leaf rust epidemic, introduces many of the book’s key arguments. The first lesson is that the outbreak and spread of the disease must be explained historically. McCook argues that the fungus arrived from East Africa in Ceylon through colonial maritime networks in a period of intensifying trade in the Indian Ocean region. On top of Ceylon’s wet climate and strong monsoon winds, the spread of the fungus was helped by the development of estate farming, which posed few physical or genetic barriers for rust spores to disperse and reproduce. The effects of deepening global integration and the ecological risks of monocropping are recurring themes in the book. The second lesson is that CLR alone seldom causes coffee production to collapse, but in combination with low coffee prices it can be fatal. From the first outbreak, farmers have devised different strategies to live with CLR, ranging from chemical control to the introduction of rust-resistant coffees. But low coffee prices could quickly make these expensive strategies unsustainable, forcing planters to abandon coffee. In Ceylon, smallholders swapped coffee for cash crops they could integrate in their farming systems, like spices, rubber, coconuts, and palm products, while estate farmers switched to tea.

The third lesson is that while CLR has thus far not affected total global coffee outputs, it has caused fundamental shifts in the world coffee market. A fascinating illustration of this is the rise of robusta coffee after 1900, which tastes rather bitter in the cup but has come to represent almost half of global coffee production. In the Dutch East Indies, CLR forced coffee farmers in the lower climatic belt to abandon coffee completely and turn to rubber instead, but growers higher up began experimenting with disease-resistant varieties introduced from Africa, most notably robusta. Within decades, most farmers in Java and Sumatra had replaced their arabica stands with robusta, forcing European and American coffee markets to adapt. This period also witnessed the start of scientific efforts to breed disease-resistant hybrids of robusta and arabica varieties, of which Timor and Catimor are successful examples. The turn to robusta continued in Africa, where colonial governments began to stimulate coffee production based on naturalized and introduced cultivars as global demand for coffee increased after World War One. It soon became evident that endemic rust limited settler-dominated arabica cultivation to a few highland areas, whereas predominantly African-grown robusta thrived in the lower climatic belts. Major African producers, like Angola, Congo, Côte d’Ivoire, and Uganda, pushed increasing amounts of robusta onto the market, shaping the taste of ordinary coffee blends and southern European espressos alike.

The final chapters of the book, dealing with the post-war period, are strongly focused on efforts to manage CLR in Latin America, for which McCook has been able to rely on a large body of scientific literature. While they lack the compelling narrative flow of the earlier chapters, McCook effectively highlights the similarities between recent and earlier containment strategies, especially the expense and limitations of chemical control and the vulnerability of coffee farmers to the vagaries of the global market, with economic uncertainty resulting in poor crop management, neglected farms, and continued planting of varieties susceptible to CLR. The book ends on the sour note that coffee companies and consumers push farmers to grow high-quality arabica coffees, whereas the threat of CLR and global warming makes this increasingly difficult. This is a magnificent study that should of interest to global and environmental historians as well as social and agricultural scientists.