Disease could wipe out bananas

Simon Rotich, a worker at Perkerra irrigation scheme farm in Marigat, Baringo Central district, tends tissue culture bananas. Photo/ANTHONY OMUYA

Banana farming is under threat from a deadly disease that could ruin the livelihoods of people who rely on the crop as staple food and a source of income. A study published in the May edition of the Plant Disease Journal shows Banana Xanthomonas Wilt, code-named BXW, threatens to destabilise food security for about 100 million people and incomes to millions of farmers in the East and Central Africa.

In Nyanza province, the disease could adversely affect Kisii highlands that produces more than 80 per cent of national banana supply. Reports from the Ministry of Agriculture indicate that yields for the crop have greatly gone down in the area. The situation is expected to worsen as farmers have been slow to adopt technologies such as tissue culture, the introduction of seedlings to a solution that makes the crop disease-resistant.

Because existing banana plants are reproduced from cuttings, there is little genetic diversity. Diseases, in particular fungus, can wipe out entire production regions. The use of suckers of affected plants or soil does not help as the crop dies a few months after planting.

Developing disease-resistant varieties is another cost-effective and sustainable way to manage the disease, according to agricultural experts. However, traditional breeding methods are less profitable as they take longer to achieve usable output.

Kenya produces over one million tonnes of bananas annually, but loses over 40 per cent to pests, poor harvesting techniques or lack of markets. In Uganda, production has nearly halved, and the trends are similar in Tanzania, Rwanda and Burundi, where banana are a major calorie source.

Uganda produces 10 million tonnes annually with an estimated value of $1.7 billion, making it the world’s second largest banana producer after India. The study, published by the American Psychopathological Society, says Kenya is at risk of the disease and the impact would be extreme since it causes the death of the mother plant that would otherwise contribute to the ratoon plant production cycles.

Though the ministry of Agriculture has received the disease alert, not much has been done. Attempts to reach Kisii district agriculture officer were not successful as he was said to be out in the field. BXW, a bacterial disease, was first reported in Uganda in 2001. It has since been reported in Kenya, DR Congo, Rwanda, Tanzania, and Burundi, which constitute the largest banana-producing and consuming region in sub-Saharan Africa.

“BXW attacks all banana varieties resulting in absolute crop loss in some cases,” says Dr Leena Tripathi, the study’s co-author and a scientist at the International Institute of Tropical Agriculture (IITA). What should put banana growing Kenyans on a high-alert is the fact that Uganda has lost billions due to the disease. The report says Uganda, the only country that has analysed the economic impact of BXW, estimates an overall economic loss of between $2-8 billion in the next 10 years.

Frequent and free movement between Kenya and Uganda, experts warn, could spread the disease to Kenya. The disease causes yellowing and wilting of leaves, uneven and premature ripening of the fruits and eventually, the plants rot to their death as the deadly BXW bacteria.

It is spread by insects, wind-driven rainfall, infected planting materials and contaminated planting tools and said to be only contained through improved agricultural practices – planting clean materials, disinfecting farm tools and early removal of male flowers.

However, once a field is infected, all banana plants should be uprooted and buried and the land left fallow or planted different crops for six months. Scientists warn that banana diseases are becoming difficult to control, as they have developed resistance to fungicides.

Despite its importance as a staple food and income source for developing countries, “surprisingly little investment has been made in research in the past on bananas,” says the report. Commercial interests in breeding better bananas had “waned after many failed attempts,” because banana is a particularly difficult crop to breed on account of its sterility and lack of seeds.

Higher yields

Scientists at IITA and Bioversity International are working with a global network of plant breeders to develop new banana varieties for African farmers that offer both disease-resistance and higher yields while matching local standards for taste and quality.

The researchers have also developed inexpensive and environmentally friendly management practices for protecting plants from disease infection. Although genetically modified varieties are already being grown in Uganda, they are yet to be released for planting in Kenya.

A more common practice is tissue culture, being promoted by Dr Florence Wambugu, the chief executive officer of the Africa Harvest. Her projects in tissue culture have changed banana growing trends in Kenya. Africa Harvest, KARI, and learning institutions like JKUAT, and UON produce tissue cultures for sale.

Dr Wambugu says the crop matures in nine months, which guarantees farmers coordinated harvesting and marketing. She says the bananas have an average yield of 14 tonnes per hectare with a potential of between 30 and 40 tonnes per hectare.

Figures from the Ministry of Agriculture shows that the area under banana production rose from a low of 43,000 hectares in 1996 to 82,000 hectares in 2006. This has resulted in an additional income of Sh5.5 billion to banana farmers over the last 10 years.