THE PROCESS IN MOTION

How does coffee wilt disease kill a canephora?

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

▶ Play the process01In the soil, a wound02The tourniquet03Dying from the top, stem after stem04What carries it05Uproot, wait, replant

In the soil, a wound

The coffee wilt fungus lives in the soil. It enters through wounds of the collar, the base of the stem at ground level, and through those of the roots. The word says the mechanism: a mycosis, that is, a disease caused by a fungus, which settles in the conducting vessels of the tree.

Read the stages without animation

1. In the soil, a woundThe coffee wilt fungus lives in the soil. It enters through wounds of the collar, the base of the stem at ground level, and through those of the roots. The word says the mechanism: a mycosis, that is, a disease caused by a fungus, which settles in the conducting vessels of the tree.
2. The tourniquetThe fungus colonizes the vessels that carry water from the roots to the leaves and blocks that rise. It is a tourniquet: the leaves yellow and curl for lack of water, though the soil is not short of it.
3. Dying from the top, stem after stemThe tree defoliates and dies from the top, stem after stem on a plant that carries several. Cut, the bark shows a black band from bottom to top; cankers split the collar; the cherries ripen too early and stay on the tree.
4. What carries itThe dead tree stands upright, unlike a plant killed by armillaria. The fungus, for its part, travels with the wind, runoff water, soil and moved plants, coffee husks used as mulch, dead wood gathered for fire and uncleaned tools. In Uganda, the disease detected in 1993 affected up to 90% of plantations.
5. Uproot, wait, replantThere is no chemical remedy. The Ugandan manual prescribes uprooting on the spot, burning, a ban on husk mulch, disinfecting tools with bleach or fire, eighteen months to two years without coffee on the plot, then resistant clones on a new plot. About 56% of the country's canephora has been destroyed.

To remember: It is not the dryness of the soil that kills the tree, it is the plug in its vessels: it dies of thirst in moist earth.

In history: This pressure is what made Uganda the country of the ten resistant KR clones.

Read the full article and its sources ↓

UCDA 2019, table 21, p. 89 (simplified reading)

The disease that redrew African canephora is called coffee wilt disease, or tracheomycosis. The word says the mechanism: a mycosis, that is, a disease caused by a fungus, which settles in the conducting vessels of the tree. The agent is the fungus Fusarium xylarioides, whose sexual form bears the name Gibberella xylarioides.

It was first observed in 1927 in Ubangi-Shari, today's Central African Republic, on an excelsa plantation. Barat, in the diseases chapter of Coste's treatise, reports that it had almost completely destroyed 15,000 hectares of excelsoids in 1942. The cause, for its part, was confirmed only in the late 1940s: plantations were seen dying long before anyone knew what was killing them.

These first waves wipe out the excelsa of the Central African Republic and Cameroon, then spread to the canephora of the Belgian Congo and Côte d'Ivoire. Against a soil fungus, there is nothing to spray: the only way is the plant itself. From the 1950s, the Boukoko station therefore looks for resistant individuals, and retains two, B10 and A445.

Then the disease goes quiet for decades. It reappears in eastern Congo in the mid-1980s and crosses the Ugandan border. Detected in 1993, it affects up to 90% of plantations and destroys about 56% of the country's canephora. About one Ugandan canephora in two, destroyed where the species is at home.

Coste 1955, p. 348 and the chapter on diseases (Barat) via LC ch. 4; Rutherford, Phytopathology, 96 (6), 2006, p. 663; Peck and Flood, “Coffee wilt disease: the forgotten threat to coffee,” Plant Pathology, 2024; UCDA 2019, § 1.2, p. 4 and § 7.1, p. 83

The mechanism is that of a tourniquet. The fungus lives in the soil, enters through wounds of the collar and roots, colonizes the vessels and blocks the rise of water: the leaves yellow and curl, the tree defoliates and dies from the top, stem after stem on a multistem plant; the cut bark shows a black band from bottom to top, cankers split the collar, cherries ripen prematurely and stay on the tree, and the dead tree stands upright, unlike a plant killed by armillaria.

There is no chemical remedy. Spores travel with the wind, runoff water, soil and moved plants, coffee husks used as mulch, dead wood gathered for fire and uncleaned tools. The manual therefore prescribes uprooting on the spot, burning, a ban on husk mulch until the disease is eradicated, disinfecting tools with bleach or fire, eighteen months to two years without coffee on the plot, and replanting with resistant clones on a new plot. It is this pressure that made Uganda the country of the ten KR clones.

UCDA 2019, § 7.1.1 to 7.1.3, p. 83-84, figures 50-51

Rust, for its part, exists on all Ugandan canephora between 1,000 and 1,500 meters, some cultivars being more susceptible than others. The manual nevertheless judges chemical treatment unprofitable on canephora, unlike arabica: the fungicide would cost more than the harvest it saves. The answer therefore lies in resistant clones and orchard management, not in the sprayer.

Red blister, caused by Cercospora coffeicola, has been reported only in the lowlands of Uganda and the Bukoba region of Tanzania. It is a lowland affair, not a hillside one.

The array of insects is detailed in the plate on diseases. Let us note here the link with climate. Prolonged drought and heat increase the vulnerability of Ugandan canephora to the black twig borer (Xylosandrus compactus) and to coffee wilt disease. In Asia and Brazil, they worsen root-knot nematodes. In other words, part of the health risk is played out on rainfall before it is played out on treatments.

UCDA 2019, § 7.2-7.3, p. 85-86; Kawuki et al. 2026, introduction