Causal Agent: 

Fungi Cercospora canescens)

Characteristic Symptoms:
 
Leaf spots are circular to broadly irregular, reddish brown.
   
During heavy infestation, the leaves have leathery, dark-reddish-purple appearance.
   
Under warm and wet conditions, the lesions coalesce and the leaves may appear blighted.
   
Conditions for Disease Development:
 
The disease is common in humid tropic and subtropical regions.
   
The pathogen survives between crops on crop debris.
   
Conidia/spores are air-borne and are disseminated by wind, rain splashes, tools/implements and field workers.
   
Infection requires free water and is favoured by temperatures between 26-32°C, in which the disease develops rapidly with new infections occurring every 7-10 days.
   
Management and Control:
 
Good field sanitation (i.e., remove and destroy infected plants/plant parts) can help eliminate inoculum sources in the field.
   
Crop rotation with non-host crops for 2-3 years will ensure elimination of inoculum in crop residues.
   
A regular spray program of copper-based fungicides (e.g. Cupravit®, Super BlueⓇ, Vitigran blueⓇ, FunguranⓇ, KocideⓇ, Hydroxide superⓇ) and chlorothalonil (e.g. Daconil®, Agronil®, Yoda®, Rover®, Yoda 500Ⓡ) may help reduce incidence and severity especially when crops are susceptible and conditions are favorable for disease development.
   
Use resistant varieties, if available.

To view other diseases,  click here.

Need more help?  Ask the Doctor.