Black Sigatoka Disease (BSD) is a fungal infection of the banana leaf which has plagued Dominica’s banana and plantain crops. In the wake of the Erika disaster, it is even more important to support the rebuilding of Dominica’s agriculture sector by such projects inspired and directed by collaboration between Dominicans, and friends of Dominica, at home and abroad.
BSD first identified in Dominica in 2012 is caused by the fungus Mycosphaerella fijiensis similar to Mycosphaerella musicola the cause of Yellow Sigatoka which we have usually called banana leaf spot. BSD affects both highly susceptible Cavendish banana cultivars such as Robusta and Giant Cavendish as well as plantains to a lesser extent. M. fijiensis is more aggressive than M. musicola and replaces it in countries it has invaded.
Infection begins on the young leaves as they emerge at the top of the plant and results in major necroses of leaves, destruction of photosynthetic leaf tissue, early immature ripening, and yield loss.
In our highly humid tropical environment there are two strategies for BSD control, fungicide control and selection of suitable resistant cultivars. Fungicide control is very expensive for cost of fungicides, labour cost as well as frequency of spray cycles. The two strategies can run currently..short term use of fungicides, good agronomic practices (soil testing, fertilizers, drainage, field sanitation, proper calibration of ground mistblowers etc) and longer term field testing and provision of resistant cultivars to farmers. For fungicide control optimal sprays should depend on single fungicides or mixtures of mostly systemic fungicides with different modes of action in banana spray oil or oil emulsions, a workable biological forecast system to reduce number of sprays and laboratory testing to detect early any development of fungicide resistance. Forecasting has been known to reduce sprays from over 40 per year to less than 10. We will need trained field personnel to do forecasts on weekly basis.
So for existing Cavendish and plantain farms and any new plantings. e.g with recently imported tissue culture Cavendish cultivars from VITROPIC in France, fungicide sprays will be necessary. Longer term solution will depend on partially resistant cultivars and/or genetically modified bananas. Dr Clayton Shillingford with collaboration of Errol Emanuel and Dr Davison Lloyd are field testing nine banana and two resistant plantain cultivars obtained from BIOVERSITY INTERNATIONAL, Belgium, the world’s largest Musa collection, to determine suitability for cooking, ripening for domestic and export markets and agroprocessing. The resistant cultivars seen here were weaned and hardened in DAPEX shade house, Fond Cole and are now planted in the field for evaluation..(rate of leaf emergence and total leaves, ratooning rate, measure of BSD compared to Cavendish cultivars, plant height at shooting, bunch weight and configuration, hand and finger size and shape etc). to be followed by cooking and ripening and organoleptic tests for taste, sweetness, texture etc. Water shortage is an important limiting factor in agriculture and the problem is likely to get worse as a result of climate change. Irrigation is routinely used but we will also field test the cultivars by phenotyping for drought.
Rebuild Dominica is supportive of the efforts to combat black sigatoka. We intend to promote the best practices in agriculture and industry. We have made a start. Donate here and help us finish the job!