THE PROCESS IN MOTION

How did a fungus that survives only on a living leaf go around the world?

Start the scene or choose a stage. The animation simplifies the mechanism; what follows gives the details and the available references.

▶ Play the process01At home, in Ethiopia02Along the shipping lines03Puerto Rico, then Africa04The Brazilian barrier05The whole continent in thirteen years06Hawaii, the last one

At home, in Ethiopia

Before 1869, rust lives in the highland forests of southwestern Ethiopia, on scattered and varied coffee plants, in stable coexistence. The cultivated coffee of the whole world came out through Yemen, dry, irrigated at the foot of the trees: McCook speaks of an ecological filter, a stroke of chance that kept rust at bay for two centuries without making the plants resistant.

Read the stages without animation

1. At home, in EthiopiaBefore 1869, rust lives in the highland forests of southwestern Ethiopia, on scattered and varied coffee plants, in stable coexistence. The cultivated coffee of the whole world came out through Yemen, dry, irrigated at the foot of the trees: McCook speaks of an ecological filter, a stroke of chance that kept rust at bay for two centuries without making the plants resistant.
2. Along the shipping linesAfter Ceylon in 1869, the disease follows shipping lines and not winds: Travancore in southern India in 1872, Sumatra 1876, Natal 1878, Fiji 1879, Timor 1886, Philippines 1890, New Guinea 1892, Samoa 1894, and back to Africa through the Usambara. Java replaces its arabicas with canephora.
3. Puerto Rico, then AfricaPuerto Rico eradicates it in 1903, the first and only documented case: the parasite is deprived of all its living hosts for long enough, on an island whose entry points are controlled. In Africa, the fungus reaches the Congo around 1913, Ivory Coast in 1951-54, Liberia in 1955, Nigeria in 1962-63 and Angola in 1966, the last lock before Brazil.
4. The Brazilian barrierRust is detected in Bahia in 1970. The sanitary barrier, buffer zone, movement controls and uprooting, is breached as early as 1971: a border cuts neither the wind nor the seasonal workers who carry the spores on their clothing, and the spot is seen only three weeks after infection.
5. The whole continent in thirteen yearsAll Brazilian regions are reached in 1975; then Nicaragua and Ecuador in 1976, Peru and Bolivia in 1978, El Salvador in 1979, Honduras and Guatemala in 1980, Mexico in 1981, Colombia and Costa Rica in 1983.
6. Hawaii, the last oneThe last unaffected territory was Hawaii. Rust is found on Maui in October 2020 and reaches Lanai, Oahu, Molokai and Kauai within nine months. It is now recorded in about 70 countries.

To remember: An organism unable to survive outside a living leaf went around the producing continents in a little over a century, carried by people.

In history: Without canephora, born of rust, McCook estimates current world production would be 30 to 40% lower.

Read the full article and its sources ↓

• Before 1869, Hemileia vastatrix lived in the highland forests of southwestern Ethiopia on scattered and varied coffee plants, in stable coexistence. The cultivated coffee of the whole world came out through Yemen, dry and irrigated at the foot of the trees: McCook speaks of an ecological filter, a historical accident that kept rust at bay for two centuries without conferring any immunity on the plants. After Ceylon
• 1872the disease follows shipping lines, not winds: Travancore (southern India)
• 1876Sumatra
• 1878Natal
• 1879Fiji
• 1886Timor
• 1890Philippines
• 1892New Guinea
• German Samoa 1894, and back to Africa from the east, in the Usambara mountains
• 1910in 1893-94. The Dutch East Indies lose half their exports between 1883 and 1887 and are down to 15% of the 1883 level
• Réunion loses 75% of its production in the 1880s and 1890s. Java replaces its arabicas with canephora introduced from the Congo around 1900, and India and Java switch to canephora; without this species, born of rust, McCook estimates current world production would be 30 to 40% lower (see canephora).

McCook 2019, p. 12-13, 66-70, 112 and 202; Vos, review of McCook (2022); LC ch. 12-13

Puerto Rico eradicates rust in 1903:

• the first and only documented case. The principle rests on the biology of the obligate parasite (removing all its living hosts for long enough)
• the conditions on geography (an island whose entry points can be controlled, a focus caught early, an administration able to impose destruction). Barat could still write in 1955 that rust was absent from the Antilles and from the whole American continent. Papua New Guinea believed three times that it had got rid of it. In Africa
• the fungus reaches the Congo around 1913 (noted in 1918)
• Ivory Coast in 1951-54
• 1955Liberia
• Nigeria in 1962-63 and Angola in 1966 according to McCook (1930 according to the BSPP table), the last lock before Brazil.

McCook 2019, p. 69 and 138; Coste 1955, p. 224 and 226; Wikipedia, “Hemileia vastatrix”; BSPP 2022, p. 6, table 1; LC ch. 12-13

Rust is detected in Bahia in 1970 by a plant pathologist returning, coincidence or not, from a tour of Angola.

Brazil had nonetheless built a sanitary barrier: buffer zone, movement controls, uprooting. It was breached as early as 1971.

It is worth understanding why such a barrier could not hold. An administrative border cuts neither the wind, which carries the spores, nor the seasonal workers, who carry them too on their clothing. And detection lags infection by three weeks: by the time the spot is seen, the fungus has already swarmed.

After that, the advance is methodical. All Brazilian regions are reached in 1975. Then Nicaragua, in the Carazo district, and Ecuador in 1976. Peru and Bolivia in 1978. El Salvador in 1979. Honduras and Guatemala in 1980. Mexico in 1981. Colombia and Costa Rica in 1983.

McCook 2019, p. 36-172; BSPP 2022, table 1; Wikipedia, “Hemileia vastatrix”

Take the measure of what has just happened. In a little over a century, an organism unable to survive outside a living leaf had gone around every producing continent. It is now recorded in about 70 countries.

The last unaffected territory was Hawaii. Rust is found there on Maui in October 2020. It reaches Lanai, Oahu, Molokai and Kauai in the nine months that follow. Arms of the sea therefore do not stop it once it has gained a foothold somewhere. The affected orchards are planted with Typica, Bourbon, Caturra, Catuaí and Geisha.

McCook 2019, p. 143-146; BSPP 2022, p. 6-8 and 13 (Money 2006; Schieber and Zentmeyer 1984); Koutouleas et al., Plant Pathology 73 (2024); LC ch. 13