Banana freckle

Banana Freckle is a disease caused by the fungus Guignardia musae (telomorph) or Phyllosticta musarum (anamorph). Generally, the causal agent of disease is referred to as Guignardia-Phyllosticta sp. There are several different strains of the fungus that exist to infect different banana varieties around the globe. Symptoms include yellowing of the tissue and formation of small dark brown spots on the leaves and fruit. Within the spots, conidia or pycnidia can be found. Banana Freckle is easily propagated and spread from plant to plant by rain splash and movement of infected tissue or fruit. Management of the disease consists of cutting out infected leaves, the paper bag method, fungicide application, and proper sanitation techniques. This devastating disease is extremely relevant for the major banana exporting countries of the world. In the absence of chemical control, there is about a 78% yield loss. Banana Freckle disease needs to be carefully monitored in order to prevent further spread of the disease.

Several strains of this pathogen exist, and some are species specific. For example, the fungal strain that infects Australian bananas, Lady Finger and Bluggoe, does not infect Cavendish bananas. Individual strains are found in various locations across the globe (see “Environment” section for more information on pathogen strains). Banana Freckle is not known to infect any other types of fruits.

Symptoms typically appear after 2–4 weeks after the banana cluster has opened, and seem to be primarily localized on older leaves. Infected tissues may also yellow with age, and eventually senesce in the most severe case of symptoms. Even in the cases of minor infection, the fungus renders the banana fruit unmarketable at the loss of the grower.

Major macroscopic diagnostic signs include small brown to dark brown specks on leaves and fruits, which indicate the presence of fungal spores protruding through the infected tissues. Depending on which stage (sexual or asexual) the fungus completes its life cycle, the spots will be either pycnidia or conidia. Microscopically, these dark spots, or freckles, can range from 1 mm in diameter to 4 mm .

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