- Widely distributed throughout the banana growing tracts of Kerala.
- Nendran variety is highly susceptible.
- Appearance of a pale yellow/dark brown/black streaks running parallel to veins, especially on lower leaves.(Image1)
- These streaks enlarges to form characteristic spots having dark brownish to black, linear-oblong areas with ill-defined border, often surrounded by a yellow halo.(Image2)
- Most often, many of yellow streaks result in premature yellowing and drooping of leaves.(Image3)
- The spots on lower leaves of young plants are dark brown and oval to circular.
- Centre of the spots dries out, becoming light grey margined by narrow dark brown or black border.(Image4).
- A number of distinct spots on leaves gives a scorched appearance.(Image5).
- Several spots coalesce resulting in extensive blighting and drying of leaves.
- In severe case, the petioles collapse and the leaves hang down from the pseudostem.(Image6).
- Unfolded heart leaf and 2-3 youngest open leaves usually do not show symptoms.
- The bunch produced will be small and never matures.
Select five rows from the field at random. Select two plants from each line.. From this select lower two leaves and 4 and 5 th leaf from the top ( lower leaves are for yellow sigatoka and upper leaves for black sigatoka.) Record the leaf area damaged. Mild ,< 10 % leaf area damaged . Moderate 10-20 % leaf area damaged. Severe > 20% . In the case of black sigatoka Mild : 1- 5% Moderate 5-10% Severe >10%.
Moderate incidence for yellow sigatoka and mild for black sigatoka
Cercospora musae (Mycosphaerella musicola)
Leaf wetness, dews on veins, temperature of 23-250C, rainy days, high relative humidity (more than 80%), poorly managed crops, poor and badly drained soils, close planting etc. help in the sudden outbreak of the disease.
- Cut and burn all moderate to severe infected lower leaves in the case of yellow sigatoka. In the case of black sigatoka cut and remove the leaves as soon as the initial symptoms are observed.
- Grow resistant/less susceptible varieties such as BRS 1,BRS 2 and Manjeri Nendran 2.
- Spray 1 % Bordeaux mixture soon after the appearance of the initial symptoms of the disease along with stickers or 0.4 % mancozeb or heavy oils like Mobil oil A.F., Gas oil, White oil or mineral oil @ 3ml/L. However, in some varieties symptoms of oil phytotoxicity may occur which consist of varying levels of leaf flecking and general bronzing of leaves.
- Spray carbendazim @0.05% or give alternate spraying of Tridimorph (0..1 % Calyxin) soon after the appearance of the initial symptom.
- Tilt (propiconazole) 0.1% has become very popular for the management of these leaf infections. However, the continuous uses of systemic fungicide can result in the formation of resistant strain of the pathogen. This can be avoided by alternating the use of systemic fungicide with 1% Bordeaux mixture.
- The number of sprays to be given depends on the severity of infection. When more than one spray is required follow a rational rotation of systemic and non systemic fungicides.
- Spray bio agents such as Pseudomonas 20 g/L or Bacillus subtilis 5 g/L .