Yellow sigatoka disease is caused by Mycosphaerrela musicola. It is characterised by appearance of small yellow specks (1-
2mm long) on the leaf, parallel to the secondary veins of the blade.

The Yellow specks develop into necrotic spots, which are more or less round and are surrounded by a yellow halo.
The necrotic pathes may go up the leaf.

The lesions on most susceptible clones past through six stages to maturity

  • Minute yellowish green specks
  • Specks grow into yellowish green to yellow streaks,visible on the upper side of the leaf
  • The streaks expand and gradually change to brown orrusty red spots with undefined margins
  • The spots obtain a definite outline with a brown centre and a yellow to light brown halo sometimes with awater soaked centre
    The dark centre sinks and the water halo turns darker brown
  • The sunken central area turns grey and is surrounded by a dark brown or black border with a yellow halo
    between the border and the normal green leaf.

 

Black sigatoka is caused by Mycosphaerella fijiensis. The disease cycle also passes through six stages to maturity largely
similar to those of Yellow sigatoka.

The main difference is at streak stage where Black sigatoka streaks are brown while those of Yellow sigatoka are initially yellow.

This similarity makes it difficult to distinguish the two diseases by symptoms alone.

The disease is characterised by early death of the banana leaves, the appearance of large brownish coloured streaks on
the underside especially of the fourth leaf.

In the absence of control, these streaks which are numerous,coalesce, with black necrotic patches amearine on topside of

the leaf.The blackened (necrotic) areas dry out rapidly and turn brown.

When soaked by rain they tend to become much darker and give the plantation such an unsightly appearance of black dead leaves

This disease usually occurs in plantations planted on cleared forestland. It is caused by a fungus ArmiIIaria sp.which also survives on some tree species.

It persists in stumps and roots of cleared trees, and later invades planted bananas through corms and roots.Aerially, its symptoms resemble those of barium wilt (yellowing and death of bananaleaves).

Examination of the corm however reveals white strands of a fungus.Sometimes toadstool-like threads appear at the base of the plant.

The spread of this disease can be reduced by uprooting and burning infected  plants, and planting
replacement a few metres from the infected site.

Anthracnose is a disease caused by a fungus Colletotrichum musae and attacks the fruit.

It is most common on cooking bananas. Its symptoms include initially, small black circulm specks on the flowers and skin, and distal ends of banana hands.

The damage increases in size and later become sunken and coalesces, forming large spots on the surface.

As the fruit matures, typical spots develop. In severe cases the fruit is entirely covered with dark blemishes.

It is however observed that only the cosmetic value is lost. The quality of pulp is not affected by the disease. However, for expoa .fruits,

It is a major disease because affected fruits are rejected.Export fiuits require treatment with fungicides recommendations of which vary with distributors in the consumer country.

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article thumbnailFarmers in the East African Highlands, centred on Uganda, depend on bananas as a staple food crop and a source of income. The harvest, however, is threatened by many pests and diseases that also...
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The vast majority of the bananas currently grown and consumed were not conventionally bred but are selections made over probably thousands of years from naturally occurring hybrids. Cultivated bananas are very nearly sterile and as a consequence are not propagated from seed but rather through vegetative propagation, primarily suckers as well as more recently micropropagated or tissue cultured bananas. These factors, very old selections, near sterility and vegetative propagation, mean that these bananas have not been genetically improved either for resistance or improved quality and are becoming increasing in affected by serious pests and diseases.

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