Panama disease

What you are looking at

Yellowing that starts on the oldest, lowest leaves of a banana plant and works its way upward, each leaf collapsing and hanging down around the pseudostem as it dies. The pseudostem itself often splits vertically near the base as the internal tissue collapses, and cutting across it reveals brown or reddish-brown streaking through the vascular tissue, the clearest single diagnostic sign. New growth on a badly affected plant is stunted and distorted, sometimes producing no fruit at all, and there is no recovery once symptoms are visible. Within a plantation, the disease typically starts in isolated plants and spreads outward in an expanding patch over successive growing cycles.

One fungus, two crises a century apart

This fungus has already reshaped the global banana trade once, and current events suggest it may do so again. An older strain, known as Race 1, spread through Central American plantations in the early twentieth century and proved so destructive to Gros Michel, the dominant export banana of the time, that growers abandoned it commercially in favour of Cavendish, which resisted that strain. Cavendish has been the banana sold in most of the world’s supermarkets ever since, propagated as a genetically uniform clone across enormous monoculture plantations.

A newer strain, Tropical Race 4, attacks Cavendish just as effectively as Race 1 attacked Gros Michel, along with most other cultivars. First identified in Southeast Asia around 1992, it has since reached the Middle East, parts of sub-Saharan Africa, the Northern Territory and Far North Queensland in Australia, and Latin America, confirmed in Colombia in 2019, Peru in 2021 and Venezuela in 2023. The major Central American and Ecuadorian export belt supplying most of Europe and North America’s bananas remains free of it for now, and losing that fight would be a considerably larger crisis than the one Gros Michel growers faced last time, given how much of world banana production depends on a single susceptible variety today.

What to do about it

Plant only certified, disease-free tissue-culture material, since infected planting stock is a primary route the fungus travels by.

Practise strict biosecurity on tools, footwear, vehicles and irrigation water moving between plantings, particularly where entering from or travelling toward an area of unknown status.

Destroy a confirmed infected planting in place rather than moving material off site, and abandon that ground for banana growing indefinitely; there is no way to clear the fungus from infested soil.

Grow a resistant or tolerant cultivar where Tropical Race 4 is already present, accepting the trade-offs against Cavendish’s yield and market familiarity.

Report a suspected finding in an area currently free of the disease immediately rather than treating it as routine crop failure.

What it gets mistaken for

Frost blackens and collapses banana foliage overnight, uniformly and tied to a specific cold event, without the internal vascular streaking this disease produces.

Root and collar rot follows waterlogged soil and softens roots and the stem base without the reddish-brown streaking inside the pseudostem that marks this disease specifically; cutting across the stem is the fastest way to tell the two apart.