A few Asian countries, including Thailand and Peninsular Malaysia, seem to be free of banana bunchy top, in that plants growing in these countries do not show symptoms of disease. However, many of the plants react to monoclonal antibodies. It is possible that they are infected with mild strains of the virus, carried by symptomless plants.
In most countries, bunchy top symptoms are severe. Infected banana plants have a congestive rosette appearance with narrow upright leaves, hence the common name "bunchy top". Plants infected early in their growth remain stunted and bear no fruit. Those infected at a later stage of growth may bear fruit, but the hands will be smaller than normal.
Aphids feeding on a diseased plant move onto healthy plants, taking the virus with them. Since infected plants serve as a source of inoculum, it is important to destroy them immediately. Just cutting the plants down is not enough. Suckers may regenerate, carrying the same virus as the source plant. Plants infected with virus must be killed. One cheap and effective way of doing this is to use kerosene. About 200 ml (a cupful) is poured into the banana plant at the growing point. Less can be used for smaller plants (100 ml for plants around 1 meter high, 50 ml for suckers). The kerosene goes down into the plant tissues. It kills the plant after five days to a week. After the kerosene is applied, it also kills any aphids which may be on the plant. When the plant is dead, the farmer should dig out the rhizome (root) and cut it into pieces. This is the only way to prevent plantlets from regenerating.
Special herbicides for killing banana plants can also be used, but they are more expensive. They are usually applied by injecting them into the stem. They kill the plant completely, so there is no need to dig out the root. However, they do not kill the aphid vectors. If growers decide to use a herbicide, they should spray the plant first to kill any aphids.
Index of Images
Figure 1 Banana Aphid, Vector of Banana Bunchy Top Virus
Figure 2 Banana Plant on the Right Has Banana Bunchy Top Virus Disease. Note the Small Upright Leaves and the Small Size of the Hand.
Figure 3 Suckers Infected with Banana Bunchy Top Regenerating from Cut Banana Plant