Plant so that the rows run in the direction of the prevailing wind, to allow air into the plantation to dry leaf surfaces, to prevent infection, or to reduce the number of spores.If planting on hillsides, choose sites with morning sun to dry leaves rapidly.Avoid areas where there is shade from trees.Avoid areas with heavy clay soils where surface water remains for some time after rains. 2nd Edition, gives details of the methods to use ( ).Ĭultural methods of control are very important the strategy is to reduce the humidity in the plantation, reducing the time that the leaves are wet and the spores can germinate and infect. The FAO/IBPGR Technical Guidelines for the Safe Movement of Germplasm. Plants of many varieties of bananas, tested to internationally agreed standards, can be obtained from the INIBAP transit centre in Belgium, and from IITA, Nigeria.
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Banana plants should only be transferred between countries as tissue cultures tested to ensure that they are free of all known banana diseases. There is also evidence that the disease can be spread by contaminated fruit shipments, especially if dead plant material is present.Ĭountries still free from black Sigatoka should take all practical measures to prevent its introduction and further spread. Spread also occurs on infected planting material. Short distance spread within the plantation is thought to be by conidia, whereas ascospores are responsible for spread over longer distances. They are released during rains or during times of high humidity and are blown in wind and rain on the underside of the emerging leaves, and the cycle begins again. Spores are produced in the dead, grey areas on the upper leaf surface.
There are two types of spores: ascospores and conidia (see diagram) the ascospores are the more important.ĭifferent strains of the fungus (plus and minus) come together to form the sexual ascospore stage (see Diagram). The fungus grows within the leaf, killing plant cells, before returning to the surface to produce more spores. The spores germinate and the germ tubes enter through natural openings in the leaf.
As the leaves mature, they become resistant.
Young fully expanded leaves on mother plants and suckers are the most susceptible to infection. Generally, the streaks are more common at the tips and edges of the leaves (Photos 2&3). In severe infections, spots do not occur, but large areas of the leaf turn black and die. The infected areas invariably form bands several centimetres wide on either side of the midrib. The spots join together, often with yellow areas between. These form spots, 20-30 mm long, with grey or light brown centres and dark brown or black margins, best seen on the upper surface (Photo 1). Red-brown or black streaks appear on the underneath of the third or fourth youngest leaf.