_____________________________________________________________________ 

This leaflet is produced by the Ministry of Agriculture & Livestock, Solomon Islands, with support 
from IPPSI: 

Improved Plant Protection in Solomon Islands, a project financed by ACIAR, the 

Australian Centre for International Agricultural Research, Canberra. Authors: Helen Tsatsia, MAL & 
Grahame Jackson, TerraCircle.

 

Extension Fact Sheet 2: 

Black Sigatoka 

 

 

 
Common name: Black Sigatoka or Black leaf streak 

 

Scientific name: 

Mycosphaerella fijiensis 

 

Hosts

: 

The fungus infects bananas and plantains, 

Musa species. 

 

Damage 

 

Red-brown streaks appear on the underneath of the third or forth youngest leaf. These 
form long spots with grey or light brown centres and dark brown or black margins 
(photo, right). The spots join together, often with yellow areas between. The infected 
areas often form bands several centimetres wide on either side of the midrib. In severe 
infections, spots do not occur, but large areas of the leaf turn black and die. Generally, 
the streaks are more common at the tips and edges of the leaves (photo, left). 

 

The effect of the disease is a loss of leaves: leaves die early. Instead of lasting 200 
days they last only 50. This reduces yield by 35-50%, depending on severity of the 
infection and on the variety. Cavendish varieties are particularly susceptible and these 
are grown for sale worldwide. About 30% of the production costs in commercial 
plantations are spent on fungicides to control the disease. 

 

The weight of the bunch and the ripening of the fruit are affected by the number of 
leaves on the plant: if too few at flowering then bunch weight is low. If less than five 
leaves at harvest, the fruits do not ripen properly: they may ripen early. 

 

Biology and Life Cycle 

 

Spores are produced in the dead, grey areas on the upper leaf surface. The fungus has 
two type: ascospores and conidia (see diagram

1

). The ascospores are the most 

important. They are released from the upper leaf surface when there is rain or high 
humidity. They travel by air currents or rain splash, and land on the underside of the 

                                                 

1

 The diagram of the life cycle is from APSnet Education Center.  Back Sigatoka of bananas and plantains. The permission of 

The American Phytopathological Society to use this diagram is gratefully acknowledged. 
http://www.apsnet.org/education/LessonsPlantPath/BlackSigatoka/default.htm 

 

 
 

_____________________________________________________________________ 

This leaflet is produced by the Ministry of Agriculture & Livestock, Solomon Islands, with support 
from IPPSI: 

Improved Plant Protection in Solomon Islands, a project financed by ACIAR, the 

Australian Centre for International Agricultural Research, Canberra. Authors: Helen Tsatsia, MAL & 
Grahame Jackson, TerraCircle.

 

emerging leaves. The spores germinate and the germ tubes enter through natural 
openings in the leaf. The fungus grows within the leaf, killing plant cells, before 
returning to the surface to produce more spores.  
 

Signs and Symptoms 

 

On leaves, a rapid development of red-brown and yellow streaks, drying from the 
margins back to the mid-rib, and early death of leaves, are typical of this disease. 
 

Management 

 

Cultural control: 
A number of measures are 
recommended to allow more 
air into the plantation to dry 
the leaf surface, to prevent 
infection, or to reduce the 
number of spores: 

•  Cut off leaves (if more 

than 50% infected) or cut 
out parts of leaves; 

•  Plant at wide spacings;  

•  Weed regularly; 

•  Cut out suckers, leaving 3-

4 plants of different sizes per plant; 

•  Remove and burn old infected leaves;                                                     

•  Use a mulch to improve plant health. 

 

Resistant varieties: 
Many plantains in Solomon Islands are either resistant or partly resistant to Black 
Sigatoka disease. However, if farmers want to grow varieties with Cavendish qualities 
for household use or the market, then they should ask MAL. The Honduran 
Foundation of Agricultural Research has bred varieties, for example, FHIA-1; FHIA-
2, FHIA-3. These are dessert or dessert/cooking bananas with resistance to Black 
Sigatoka.  

 

Chemical control: 
Fungicides are only recommended for commercial plantations, these are: 
 
Protectant fungicides: 

•  dithiocarbamates (e.g., mancozeb); 

•  Banana misting oil (not available in Honiara). 

Systemic fungicides  

•  triazoles (e.g, propiconazole, and flusilazole); these chemicals are not 

available in Honiara 

•  strobilurins (e.g., azoxystrobin). It is not available in Honiara 

 
It is important to rotate the fungicides in the different groups to prevent the build up 
of resistant strains of the fungus. In drier times, mancozeb can be used alone.