Disease: Yellow Sigatoka Leaf Spot

One of the most destructive banana plant diseases is the Yellow Sigatoka Leaf Spot. The disease begins with small, light yellow spots or streaks parallel to the side vein of the leaf. The disease can only infect young banana leaves. Ascospores are released after rain and are spread by wind and rain. The most important factors for disease development are moisture on young leaves, caused by dew, rain or overhead watering, together with high temperatures. Hot and humid weather encourages rapid disease development. There is an incubation period of at least a month between infection and the appearance of leaf spots. Later, as the disease progresses, the spots elongate and turn brown with light gray centers. The spots elongate more and the tissue around them turns yellow and dies. Adjacent spots coalesce to form large lesions. The pathogen survives in the infected banana leaves and spreads via the wind. The period between fungicide applications depends on the climate and the amount of yellow Sigatoka already present. In the wet season, apply a protectant fungicide every three to four weeks. Either mancozeb (Dithane) with mineral oil or  chlorothalonil (Bravp) can be used.  Only apply fungicides in amounts recommended on the label. Infected and dead leaves will produce fungal spores as long as they are left on the plant. Early removal of diseased leaves is essential. Avoid removing all diseased leaves during the hot dry season because of their beneficial shading effects.

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