Walk a coffee grove after a long, warm rainy stretch and you may spot a branch that looks as if it has been dusted with pale coral paint. The foliage past that patch has gone limp and brown, yet the dead leaves stubbornly hang on rather than dropping. That coral bloom is not a stain or a lichen. It is the living fruiting crust of a fungus, and the branch is dying from the outside in. This is pink disease, one of the more visually distinctive bark diseases of tropical tree crops, and coffee is squarely on its long menu of hosts.
Pink disease is worth understanding on its own terms because it is easy to confuse with other troubles a coffee tree can suffer. It is not a leaf disease and it is not a root problem. It works on the bark of living branches and stems, and it thrives in exactly the warm, drenched, poorly ventilated conditions that some of the world's most beautiful shaded groves create. For the wider context of the crop it attacks, our overview of coffee and its cultivation is a useful companion.
What is pink disease of coffee?
Pink disease is a fungal bark and branch disease caused by Erythricium salmonicolor (Berk. & Broome) Burdsall, a basidiomycete traditionally placed in the family Corticiaceae. The pathogen has been renamed several times as taxonomists have reclassified it, so older literature and farm bulletins may call it Corticium salmonicolor, and it has also appeared as Phanerochaete salmonicolor and Pellicularia salmonicolor. They are all the same organism. The species name, salmonicolor, literally means "salmon-colored," which is the single best clue to what you are looking at.
Unlike many coffee pathogens that colonize leaves or feed on roots, this fungus makes its home on the surface and outer layers of woody bark. It does not strictly need a wound to begin, though cracks and old pruning cuts help. Once established, it grows across and into the bark of branches and small stems, and it is the disruption of that bark and the cambium beneath it that does the damage. It belongs to the broad family of woody-tissue problems covered in our guide to coffee diseases and pests, and it sits closer to the trunk-and-branch group than to the foliar diseases that tend to get more attention.
How to recognize pink disease: from cobweb to salmon crust
The reason the disease is so nameable is that the fungus passes through a sequence of visible forms on the bark, and each looks quite different. Catching it at the first stage is the difference between snipping off one twig and losing a whole scaffold branch.
| Stage | What you see | What it means |
|---|---|---|
| Cobweb stage | A thin, silky, white-to-pale mycelial film spun over the bark during wet weather | Earliest and easiest to treat; often overlooked because it is faint |
| Pustule stage | Tiny pink pustules, roughly 1 mm across, appearing shortly after the cobweb film | The fungus is beginning to form spore-bearing bodies |
| Necator stage | Orange to red sporing pustules, often on the exposed surfaces of branches | A spore-spreading phase that seeds new infections |
| Pink encrustation stage | A continuous, smooth, pinkish salmon crust, often forming at branch forks and on the shaded underside of the branch | The mature, fully developed fungus; the branch is usually girdled by now |
Not every infection shows every stage cleanly, and the exact order can blur — on a shaded, humid branch the cobweb and pink phases may overlap. On some hosts the fungus also drives gum or latex to ooze from the bark, and the bark may split lengthwise or crack around a canker. The through-line is color: a genuine pink disease lesion trends toward coral, salmon, or dusty rose, not the dull rust-orange of a leaf-spot fungus. If you scrape a mature crust gently, it lifts away in a papery layer, revealing damaged bark underneath.
How the fungus kills a branch
The mechanics are straightforward and unforgiving. As the fungus spreads around a branch, its mat of tissue and the canker it creates encircle, or girdle, the wood. The girdle disrupts the cambium and the conductive tissue just under the bark — the plumbing that carries water and sap. Once that ring is complete, everything beyond the infection is cut off from the tree's supply line.
The result is a classic, telling picture. Leaves past the girdle wilt, yellow, and die, and the branch tip dies back toward the infection. Crucially, those dead leaves often cling to the dead wood instead of falling, because the branch died too fast for the tree to form the tidy separation layer that normally sheds a leaf. A cluster of brown, hanging leaves at the end of an otherwise green branch, with a coral crust upstream of them, is close to a signature. This branch-death outcome overlaps with the broader syndrome we cover in our guide to coffee dieback — but pink disease is one specific, identifiable cause of it, not the whole story.
Why wet, over-shaded groves are most at risk
Pink disease is fundamentally a disease of water and stagnant air. The fungus needs prolonged surface moisture on bark to spread and fruit, so it becomes serious in high-rainfall, high-humidity regions — outbreaks tend to cluster in the wettest districts, where annual rainfall runs well above 2,000 mm. It is a recurring problem in the wetter coffee, cacao, and rubber districts of Asia, in parts of Africa, and in humid pockets of the Americas. Warmth plus near-constant leaf and bark wetness is the recipe.
The grove's own structure matters just as much as the regional climate. A dense, closed, heavily shaded canopy holds humidity, blocks drying breezes, and keeps bark wet for hours or days after rain — a microclimate the fungus loves. This is where an otherwise valued practice can backfire: the cooling, biodiversity-rich shade-grown systems that many growers prize can, if the shade is too heavy and unmanaged, incubate exactly the still, damp air that pink disease exploits. It is not an argument against shade; it is an argument for managing it. Getting canopy, spacing, and airflow right in the first place is the foundation of keeping this disease rare.
Pink disease vs. leaf rust, brown eye spot, and dieback
Because "sick coffee branch" has many possible causes, it is worth being precise about what pink disease is and is not. The table below sets it against the diseases it is most often confused with.
| Problem | Pathogen / cause | What it attacks | Tell-tale sign |
|---|---|---|---|
| Pink disease | Erythricium salmonicolor (fungus) | Bark of branches and stems | Salmon-pink crust girdling a branch; clinging dead leaves |
| Coffee leaf rust | Hemileia vastatrix (fungus) | Leaves | Orange-yellow powdery spore patches on leaf undersides |
| Brown eye spot | Cercospora coffeicola (fungus) | Leaves (and berries) | Brown spots with pale centers and a yellow halo |
| Dieback (general) | Many: nutrient stress, drought, overbearing, other pathogens | Branch tips | Tip death from the outside in, no single crust or spore signature |
The key contrasts are simple. Leaf rust and brown eye spot are foliar diseases — they live on leaves, not bark, and neither produces a pink crust encircling a branch. General dieback is a symptom with many drivers and no distinctive fungal signature. And if the wilting starts from the ground and the whole tree fades rather than one branch, suspect a soil-borne problem such as root rot instead. Pink disease is defined by its color and its location: a colored crust on living bark, mid-branch or at a fork.
Managing and preventing pink disease
Control combines the surgeon's knife with weather-smart grove design. No single spray "cures" a girdled branch, so the emphasis is on removing infected wood and denying the fungus the wet, still conditions it needs.
- Prune out and burn. Cut off affected branches well below the visible infection — below where the crust or cobweb film ends, into clean wood — because the fungus can run ahead of the obvious symptoms inside the bark. Do not leave the prunings in the grove to re-seed spores; carry them out and burn them.
- Open up the canopy. Thin dense growth, correct over-heavy shade, and space plants so air moves and bark dries quickly after rain. Faster drying is genuine, ongoing prevention, not a one-time fix.
- Protect the cuts and susceptible bark. A protective copper-based fungicide — copper oxychloride or a Bordeaux-type mixture — painted or sprayed onto pruning wounds and vulnerable bark helps stop new infection from taking hold. Copper is protective, meaning it works best applied before or right at infection, so timing to the wet season matters; follow local agronomic guidance for rates and intervals.
- Scout early and often. The disease is dramatically cheaper to manage at the faint cobweb stage than at the salmon-crust stage. Regular inspection during and after wet spells, especially of branch forks and shaded lower wood, is the highest-value habit.
A disease well beyond coffee
One reason pink disease is so well studied is that coffee is only one victim among many. Erythricium salmonicolor has an unusually broad host range across tropical woody plants. It is a classic and economically serious disease of rubber plantations and of citrus — grapefruit and orange among them — and it also strikes cacao, tea, mango, apple, nutmeg, kola, and various shade and forest trees. In some outbreaks on other crops, losses have been severe. For the coffee grower this cross-crop reach carries a practical lesson: if pink disease is active on the shade trees, hedges, or neighboring orchards around a grove, those plants can act as a reservoir, and the same wet-canopy conditions that threaten them threaten the coffee too. Managing the whole planted landscape, not just the coffee rows, is part of keeping this bark-killing fungus in check.
Frequently asked questions
What is pink disease of coffee?
Pink disease is a fungal disease of the bark of coffee branches and stems, caused by Erythricium salmonicolor (formerly Corticium salmonicolor). The fungus grows over the bark and forms a distinctive salmon-pink crust, girdling the branch so that the leaves and wood beyond it wilt and die back. It is a woody-tissue disease, not a leaf or root disease.
What causes pink disease?
It is caused by a single fungus, Erythricium salmonicolor, a basidiomycete traditionally placed in the family Corticiaceae. The same organism appears in older references under the names Corticium salmonicolor and Phanerochaete salmonicolor. It infects the bark and spreads fastest under warm, very wet, humid conditions.
What does pink disease look like on coffee?
It runs through stages: first a faint, silky white cobweb-like film on the bark, then tiny pink pustules, then orange-red sporing patches, and finally a smooth pinkish salmon crust, often at branch forks. Downstream of the infection, leaves wilt and die but frequently cling to the dead branch instead of dropping — a strong clue that separates it from ordinary leaf disease.
Why does pink disease thrive in wet weather?
The fungus needs prolonged surface moisture on bark to grow, spread, and produce spores, so it becomes serious in high-rainfall, high-humidity regions and in dense, over-shaded groves where bark stays wet and air is stagnant. Sites with very heavy annual rainfall and closed canopies offer the still, damp microclimate it depends on. Drier or well-ventilated groves see far less of it.
How do you treat pink disease of coffee?
Prune out infected branches well below the visible crust, into clean wood, and burn the prunings so they cannot re-infect. Open up the canopy and reduce excessive shade so bark dries quickly and air circulates, and apply a protective copper fungicide, such as copper oxychloride or a Bordeaux-type mixture, to cuts and vulnerable bark. Early scouting matters, because the disease is far easier to stop at the faint cobweb stage than once the salmon crust has girdled the branch.