More than 70 million people in 15 countries in Sub-Saharan Africa depend on banana for their livelihood and food supply. Their food security is being threatened by the arrival and spread of two devastating banana diseases – Banana Bunchy Top Disease and Banana Xanthomonas Wilt. An international meeting was convened in August 2009 on how to respond to this spreading regional crisis.
Banana Xanthomomas Wilt (BXW) or Banana Bacterial Wilt (BBW) first reached epidemic levels in Uganda in 2001. Despite control efforts, it has now spread to many locations in Uganda and other countries of the Great Lakes region including DRC, Kenya, Rwanda, and Tanzania. Analysis from Uganda indicated that, if unchecked, the disease could result in national cumulative losses of $4 billion over a five year period.
BXW symptoms include the wilting of leaves, premature ripening of bunches and rotting of fruit, and death of the plant – damage is up to 100%. Contaminated tools, insects, and even birds spread the bacteria, but long distance transmission is often man-induced through the movement of planting material carrying latent infections. All banana cultivars are susceptible to the disease, and BXW has to be controlled through eradication or field management practices that reduce pathogen spread..
In Uganda, participatory management campaigns were initially successful in reducing infections, and in pilot villages where Farmers’ Field Schools were introduced by FAO in 2006, the disease was practically eliminated. Recently however, the disease is showing resurgences in areas where it was previously controlled, probably resulting from a form of fatigue and the lack of sustained support system and incentives to the farming communities – including availability of clean planting material. Control practices, including destruction of infected plants, removal of male buds and use of clean tools are physically onerous. Besides, more information on the disease epidemiology and spread is needed.
Banana bunchy top disease (BBTD) caused by the Banana Bunchy Top Virus (BBTV) is considered to be the most economically destructive virus disease affecting bananas worldwide. In Sub Saharan Africa the disease is now endemic in 11 countries. In Malawi, 40% loss of national banana production is now attributed to BBTD.
The virus causing BBTD is transmitted by the aphid vector as well as through infected planting materials. On mature infected plants new leaves emerge with difficulty, are narrow and wavy with yellow margins. The plants appear to be “bunched” at the top. Once established, BBTD it is extremely difficult to eradicate or manage. The only control measure is the removal and destruction of banana plants showing symptoms and which act as reservoirs of the virus. For instance, in Australia costly eradication campaigns and statutory enforcement of quarantine controls led to the disease eradication, but the risk of resurgence remains high.
Responding to the crisis
In response to these twin threats, an international workshop was convened by the Southern African Development Council (SADC) with support from FAO, the International Institute of Tropical Agriculture (IITA) and Bioversity International, in August 2009 in Arusha, Tanzania.
The workshop evaluated the current status of BBTD and BXW in SSA and the risk of their spread, as well as the preparedness of the countries and their capacity to respond to these diseases. The workshop also provided information on surveillance techniques to be used, and the follow on work will include a pilot coordinated surveillance programme in 7 countries, funded by FAO partnership programme resources, in association with IITA.
Overall recommendations included vigilance and pre-emptive action to destroy infected banana plants as soon as symptoms appear, enhanced surveillance and monitoring strategies, improved capacities to recognize the diseases and to deploy rapid eradication responses to prevent infection and further disease spread. Farmers should be sensitized to report and combat the diseases early, supported by community-level actions, with the help of local and national governments and sub-regional organizations. Systems should be put in place to supply clean planting material to farmers who had destroyed infected plants so as to safeguard and sustain production.
Building on the on-going regional efforts, FAO, IITA and Bioversity International have agreed to work with the relevant regional organizations, to further develop a banana disease management framework for sub-Saharan Africa. This will be reviewed and endorsed at a high level meeting of national stakeholders. The framework will support effective networking between all those involved in banana disease control, coordination for information gathering and sharing, and identifying national needs and gaps in funding. It will help increase awareness and in raising funds so that all disease eradication and management activities can contribute to a common goal – the management of banana diseases and improved food security across the region..