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PestNet is a network that helps people worldwide obtain rapid advice and information on crop protection, including the identification and management of plant pests. It started in 1999. Anyone with an interest in plant protection is welcome to join. PestNet is free and is moderated, ensuring that messages are confined to plant protection.
May 2008. Tissue cultured bananas in Sri Lanka have a major problem: plants of the variety Silk grow normally without showing viral or nutrient deficiency symptoms. However, they have thin fruits and small bunches. More than 95% of plants are affected by the condition. The cause was thought to be one of the following:
1. Nutriet deficiency 2. Viral diseases 3. Due to somaclonal variations
Some members thought the problem was due to fungal disease. There is a high incidence of leaf disease in the plantation (most likely Mycosphaerella eumusae). There appear to be only 4 or 5 leaves on the plants with new bunches and that will not be enough to fill the bunch. The leaves will probably die off at about one per week as they will already be heavily infected but symptoms have not shown yet. Failure of fruit to fill may simply be lack of leaves. The fingers worst affected due to poor filling are always the lower ones in the bunch, as in the photos. They will never fill. It is usually best to remove them early and save the fingers capable of filling.
Short of going to the trouble of spraying (which is rather difficult to maintain under small plantation conditions) try growing a more resistant variety such as Ducasse (Pisang Awak). See also the information on varieties in the summary under Strobilurin fungicides under Crops>Plantation crops>Banana.
Tissue cultured plants of Silk can have a problem of not being able to fill the lower hands of a bunch in the plant crop. The effect is not so marked in plants grown from large suckers or butts as they have better food reserves to get established. The differences disappear in the ratoon crops.
Have varieties FHIA 01 and FHIA18 been tried?
Others thought the condition was due to somaclonal variation. DPI, Queensland, Australia wrote, that the symptoms were likely to be a somaclonal variant. Scientists there have observed something similiar in Lady Finger, another AAB-type cultivar. They can only speculate that the mutation affects the plant’s nutrition in some way. A paper has been published entitled, Characterisation and early detection of an offtype from micropropagated Lady Finger bananas by Smith, Hamill, Doogan and Daniells (1999) Australian Journal of Experimental Agriculture Volume 39: 1017-1023.