Tuesday April 2 2013

Finding ways to deal with banana pests

By Lominda Afedraru

Ugandan farmers are faced with the pest and disease burden affecting most banana species grown in the country, ranging from the East African highland banana commonly known as matooke, sukari ndizi, bogoya and gonja. The pests considered “most dangerous” by crop scientists are weevils and nematodes.

The banana weevils, known as Cosmopolites sordidus, are found in all banana growing countries and have existed from the time farmers began growing bananas. They lay eggs at the stems and cause the trunks to rot leading to collapse of the plant.

Yield loss
According to Dr David Talengera, a banana breeder at the National Agricultural Research Laboratories Institute (NARLI) in Kawanda, the weevils destroy the core of the banana stem from the neighbouring infested suckers.

This causes water deficiency in the plant causing stunted growth leading to a 30 to 50 per cent yield loss in most farmers’ fields.

The banana nematodes are a type of roundworm, which inhibit the root system of the crop causing inability to absorb water and reduce the leaves of the plant leading to 50 per cent yield loss.

However the nematode species are very difficult to distinguish; some are parasitic while others are not.

Unlike the banana weevils, which according to the scientists, are hosted in banana plants, nematodes can be found in other crops such as maize and yams.

Destroying pests
Many parasitic nematode species cause diseases in plants, animals, and humans while other species are beneficial in attacking insect pests. Few farmers know about banana nematodes because the worms are hard to see with the naked eye.

Farmers are advised to insert a sucker, which has been prepared for planting into hot water at a temperature of 45 degrees Centigrade and apply Furadan pesticide.

The weevils can be trapped especially when the adult insects are seen laying eggs in the stems during harvesting.

“When a farmer is harvesting banana, usually they cut down the stems and split them, if the adult weevils are nearby they usually come to lay eggs on the split stem. A farmer can trap and destroy them there and then. Farmers are also advised to apply pesticides like Furadan,” Dr Talengera said.

Any means
Pests tend to infest plantations mainly in the lowlands like central Uganda but highland area like in western Uganda are less affected.

The scientists, apart from developing resistant varieties using conventional means, are also using the biotechnology to come up with transgenic varieties that are expected to be resistant.

But the challenge is having few banana varieties, which are tolerant to the pests. This is not guaranteed to eliminate the infestation rate completely.

Trait of interest
The head of the National Agro-Biotechnology Centre at NARLI, Dr Andrew Kiggundu, said farmers should also take note of the ecological locations they are in.

While explaining the zones outlined by the Ministry of Agriculture, he pointed out that low yields are also arising from poor soil fertility.

“Soil along Lake Victoria basin is degraded because fertile soil is being washed to the lake, this means farmers in this region are encouraged to grow improved varieties,” he said.

He added for the first time, scientists have used biotechnology, including breeding crops using radiation to obtain a trait of interest, in breeding varieties which are resistant to a number of pests and diseases.