Black Sigatoka Disease is considered far and away the most destructive disease to bananas and plantains. The disease affects the leaves, severely impacting the plant’s ability to produce fruit of good size and weight and causes premature ripening of the fruit, diminishing their export potential. The disease spores are carried by leaves and other planting material and as such can be spread easily from farm to farm and from country to country.
The fungal disease causes dark leaf spots that eventually enlarge and coalesce, causing much of the leaf area to turn yellow and brown. The high rainfall and humidity of the tropical regions in which bananas are grown are especially favorable for disease development. The fungus that causes black Sigatoka, Mycosphaerella fijiensis, is spread from tree to tree by wind, rain, and irrigation water. The name black Sigatoka was given to the disease because it was first discovered in 1963 in the Sigatoka Valley of Fiji.
Black Sigatoka is a difficult and expensive disease to control. It is estimated that 15-20% of the price of bananas is due to the cost of the disease control measures that are used to produce the fruit. Cultural practices such as removing diseased leaves and pruning branches to improve air circulation are also helpful in reducing the occurrence of the disease, but these practices are labor intensive.
Because fungicides are used so frequently, growers are finding that the fungus is becoming resistant to the fungicide products applied to the crop. In addition, many of the farmers that operate small plantations cannot afford to purchase fungicides. A convenient and low-cost way to control the disease would be to grow banana varieties that are resistant to the disease, but the most popular banana cultivars grown are extremely susceptible to black Sigatoka. Fortunately, banana hybrids that show resistance to this disease are being developed. More work still needs to be done to identify hybrids that produce fruit with a good shelf life and that are acceptable in taste to the consumer.
Black Sigatoka Preventive measures:
- Planting should be taken up in well drained soils and maintain proper drainage thereafter
- Grow resistant varieties
- Planting at recommended spacing
- Remove suckers periodically to avoid overcrowding and maintain only one or two healthy suckers
- Periodically remove and burn affected leaves to avoid further spreading
- Provide adequate potassium fertilizers
- Keep the fields free from weeds