Two major strategies are available to successfully
control Fusarium wilt of banana; prevention and the use of resistant varieties.
In the past 30 years, tissue culture plants and thorough phytosanitary
practices supported by empowered regulatory authorities have been keeping
banana fields free of diseases in countries like Australia. This option is
available to large-scale commercial growers with the financial means to buy such
plants, but it is seldom adopted by small-scale and subsistence growers who
cannot afford them and are forced to establish new banana fields by using
suckers. For these farmers resistant varieties, if available, are the only
option to continue farming bananas.
Preliminary steps have been taken to screen
some African cooking banana varieties for resistance to Foc TR4 in Asia, but
the full diversity of bananas produced on the continent has not yet been
evaluated. Furthermore, for the past 20 years, the Taiwan Banana Research
Institute has produced numerous Cavendish somaclonal selections with resistance
to Foc TR4. Not all of these adapt well when introduced into other countries,
but further selection has resulted in resistant Cavendish somaclones now being
planted in the Philippines and Indonesia, and there is scope to test their
suitability to African conditions. Hybrid varieties resistant to Foc races 1
and 4 have been selected by the FHIA breeding programme in Honduras. These may
be acceptable to African growers and consumers and can be included in African
breeding programmes.
Prevention and management of banana Fusarium wilt can be achieved by means of enhanced awareness, legislation, regulation, quarantine, avoidance and treatment of infested fields. These actions can take place before Foc enters countries and farms, or once it has been introduced into countries and onto farms. The activity chosen to deal with Fusarium wilt depends on the availability, affordability, geographical area and production systems in countries/farms affected and under threat of being affected, as well as general knowledge of the disease and its management. Protecting bananas against Foc TR4 (or other foreign strains) is the responsibility of a number of stakeholders, including national and regional authorities, research scientists, extension officers and producers. Activities include:
Pre-border proactive activities:
- Assessment of national biosecurity legislation and regulations
- Assessment of a country's ability to prevent and respond to incursions of Foc
- Obtaining sufficient knowledge on Foc and means to deal with it outside country borders
- Raising awareness about Foc TR4 among policy makers, government and quarantine officials, the public, researchers, banana producers and other stakeholders
- Developing standardised training manuals, identification and surveillance protocols, as well as methods to deal with Foc incursions nationally and regionally
- Developing national capacity and infrastructure to deal with incursions
- Training plant health officials, scientists, extension officers, border control and quarantine people, and producers on Foc identification and management
- Distribution of posters, brochures and information materials on Foc TR4 and other races
- Preparing technical materials on the prevention, detection, contention and eradication of Foc-affected plants.
- Introducing an emergency fund to rapidly respond to incursions
- Developing an entrance risk analysis and identify high-risk entry points
On-border:
- Evaluating quarantine measures and strengthen border control
- Including Foc TR4 as quarantine pest on national lists
- Developing legislation and phytosanitory regulation for bananas and/or parts of bananas introduced from Foc TR4-affected countries or countries at risk
- Strictly controlling the importation of banana and plantain plants and plant parts from countries affected or at risk of Foc TR4 through national quarantine stations
- Requesting in vitro plants to be accompanied by certificates for disease indexing
- Identifying and strengthening high risk entry points for banana plants infected with Foc
- Training scientists in the use of reliable diagnostics for Foc TR4 identification
Post-border activities:
Off-farm:
- Mapping of the distribution of Foc TR4 and other Foc races in banana-growing countries
- Gathering of epidemiological data to establish means of introduction and spread
- Assessing, training and introducing surveillance systems and teams in-country
- Introducing legislation to regulate the movement of banana planting materials and other risky materials within country borders
- Setting up quarantine zones to prevent the movement of infected planting materials and other possible risky materials in-country
- Collaborating nationally and regionally to prevent and manage Foc TR4 in the region.
- Organising training workshops and expert consultations with international Fusarium specialists
Farm border:
- Obtaining clean planting and propagation material from reputable sources, preferentially tissue culture bananas
- Putting up highly visible and clearly understandable signs at farm entrances to notify visitors about farm biosecurity
- Cleaning all vehicles visiting farms by hosing-off clay and plant parts and disinfection at wash-down areas before entering or leaving farm gates
- Managing the movement of farm visitors and vehicles entering farm borders by:
- Allowing visitors onto the farm only by appointment and upon signing in
- Disinfecting the shoes and vehicles of visitors
- Using only on-farm vehicles and boots provided to visitors in plantations
- Enquiring about the employment history, nationality and movement of all farm workers
- Avoiding sharing farm machinery, equipment and field tools with other growers
- Strictly controlling access of contractors and service providers to farm
On-farm activities:
Early detection and eradication:
- Training and employing scouts to identify and immediately report any suspect plants
- Properly isolating and eradicating any outbreaks of banana Fusarium wilt by fencing-in of diseased and neighbouring plants, killing of such plants and burning, and preventing the movement of soil and water outside affected areas
- Restricting and controlling movement of farm workers and farm equipment into and out of Foc-infested fields, and use disinfectants to clean shoes and plantation tools. These shoes and plantation tools should preferentially not used in other areas on-farm
- Limiting vehicle movement to designated roads and regulate routes according to areas affected and non-affected by Foc
- Abandoning further banana production in newly affected sites growing ground covers to prevent erosion and movement of soil
- Introducing protocols to identify, isolate and monitor Fusarium wilt outbreaks. This should include means to distinguish between Fusarium wilt closely related diseases.
- Preventing flow of irrigation or rain water out of affected areas by redirecting drainage canals
- Regularly testing irrigation water and planting materials to prevent further spread of banana Fusarium wilt
Options to manage Fusarium wilt in fields where Foc is already present (activities require expert advice from experienced field plant pathologists):
Biological control:
- Using of mycorrhizae, Trichoderma, non-pathogenic Fusarium oxysporum, bacteria and actinomycetes
Chemical control:
- Fungicide dipping for root protection during planting, stem injections
- Surface sterilants for disinfection purposes
- Soil fumigation
- Plant activators
Cultural control:
- Clean planting material: tissue culture and clean suckers/bits
- Proper sanitary and phytosanitary actions
- Crop rotation and fallow periods
- Soil amendments and fertilizers: pH, nitrogen, calcium, silicon, iron, organic matter
- Flood fallowing and bio-fumigants: leek, brassicas, anaerobic fumigation
- Establishment of persistent ground covers that stimulate microbial activity and prevent movement of soil and drainage water
- Suppressive soil properties: consider soil biology, chemistry and physical properties
- Proper irrigation schedules and drainage
- Fencing-in of infested fields to prevent unnecessary pedestrian and animal movement
Host resistance:
- Planting popular local varieties with natural resistance to Foc TR4
- Planting hybrids developed by conventional plant breeding: ex. FHIA varieties
- Planting varieties developed by mutation breeding: Somaclonal variants, chemical mutations and irradiation
- If acceptable to markets, plant genetically modified bananas with proven resistance to Foc TR4 (with anti-fungal genes, resistance genes, anti-stress genes, HIGS)
Integrated disease management:
- Employ mixed cropping systems
- Employ plant resistance and soil amendments
- Fumigation and the use of biological control products