What is witches' broom, and what did it do to Brazil?
A fungus that hijacks the tree's own growth, producing the deformed shoots it is named for. Its arrival in Bahia in the late 1980s collapsed one of the world's major producing regions within a decade — the clearest demonstration in cacao's history of what a pathogen can do to a monoculture.
Where it is
- South and Central America and the Caribbean
- Notably Brazil, where its arrival in Bahia reshaped the national industry
Where it is not
- West Africa — its absence is one of the reasons the region became dominant, and preventing its introduction is a standing phytosanitary priority
- Southeast Asia
Stated rather than left to be inferred. Absence is a fact about this pathogen and one of the main things that separates the threat picture of one producing region from another's.
What causes it
Moniliophthora perniciosa
Formerly classified as Crinipellis perniciosa. Older literature and much of what is written online still uses that name.
Established evidence
Supported by systematic review, meta-analysis or a regulatory or clinical position, from more than one independent original source.
What it looks like
Infected growing points produce abnormal, thickened, highly branched green shoots — the 'brooms' — which later dry to a brown skeleton that persists on the tree. Infected flower cushions produce deformed growth rather than pods, and infected pods develop internal rot and hard lesions.
The dried brooms are the diagnostic sign and are also the problem: they are where the fungus fruits.
How it spreads
Spores are released from mushroom-like fruiting bodies that develop on the dried brooms, mostly in wet conditions, and are carried by wind and rain to actively growing tissue. The fungus can only infect meristematic tissue — new flushes, young pods, flower cushions — which is why infection follows the flushing cycle.
That dependency is what makes sanitation work: removing and destroying brooms removes the source before it fruits.
What it costs
Capable of region-scale collapse rather than incremental loss, which distinguishes it from black pod. The Bahian episode is the reference case: a producing region of global significance lost the great majority of its output over a period of years, and the social consequences in the region outlasted the epidemic.
It attacks flower cushions as well as pods, so a heavily infected tree loses not only this season's crop but its capacity to set the next one.
How climate changes the picture
Fruiting and infection both require wet conditions, so pressure follows rainfall. The interaction that matters most is with the flushing cycle: infection needs susceptible new growth and rain at the same time.
How good is the evidence
The organism, the meristem requirement, the broom-fruiting cycle and the Bahian history are all well documented and consistently reported. The genus was reclassified from Crinipellis to Moniliophthora, and older writing uses the former name — which is worth knowing when reading anything published before the revision.
Where informed people disagree
- How much of the Bahian collapse is attributable to the pathogen alone as against the coincident price collapse and the region's dependence on a single crop — the epidemic and the economics arrived together.
How it is managed
These are categories of response, not instructions. This site gives no product, rate, concentration or interval for anything, and nothing here is a substitute for local agronomic advice — what works depends on the species present, the season and the regulations where the farm is.
- Phytosanitary pruning — cutting out and destroying brooms before they fruit, which is the central intervention and is labour-intensive
- Resistant planting material, which is the route Brazilian rehabilitation principally took
- Canopy management to reduce humidity around growing points
- Strict quarantine to keep it out of regions where it is absent, which is the single highest-value measure available to West Africa
Why quarantine is the whole strategy in West Africa
Witches' broom is absent from West Africa, which produces most of the world's cocoa, and the consequences of that changing would be difficult to overstate: the region's plantings are genetically narrow, the disease attacks flower cushions as well as pods, and control depends on labour-intensive pruning that a smallholder system would struggle to deliver at scale.
This is why cacao germplasm movement is tightly controlled and why quarantine facilities exist between producing regions. It is also a reason the catalogue treats the international exchange of planting material as a subject with real stakes rather than as administrative detail.
Related
Affects
- Monoculture risk in cacaoThe reference case for what uniform planting costs when a pathogen arrives — this is the episode that topic is built around.
- CriolloThe susceptibility that makes fine-flavour genetics expensive to grow where this disease is present.
- BrazilThe producing country whose industry it reshaped.
- Frosty pod rotRead alongside Witches' broom. A pod disease of the Americas whose worst feature is that it is not visible until too late: the fungus destroys the beans internally while the pod looks sound, and by the time the characteristic white bloom appears the pod has already produced enormous quantities of spores.
Covered in
- Pruning cacaoWhere removing infected material is the core of the response rather than an adjunct to it.
- Cacao clone codesThe disease pressure that made resistance donors like Scavina the most-used material in the world.
Pests and diseases
- Black podRead alongside Black pod. A fungus that hijacks the tree's own growth, producing the deformed shoots it is named for. Its arrival in Bahia in the late 1980s collapsed one of the world's major producing regions within a decade — the clearest demonstration in cacao's history of what a pathogen can do to a monoculture.
Sources
- Cacao Diseases: A History of Old Enemies and New Encounters — Springer, 2016(citation identity confirmed; passage not re-read)
- CABI Compendium: Theobroma cacao pests and pathogens — CAB International(citation identity confirmed; passage not re-read)
This page describes a crop pathogen or pest for readers of a chocolate reference. It is not agronomic advice. See the editorial policy.