Causal Agent: 

Fungi (Oidium sp.)

Characteristic Symptoms:
 
Affected leaf consists of white, talcum-like, powdery mold/pustules on the upper leaf surface.
 
Symptoms appear first on the older and shaded lower leaves. Infected leaves turn yellow, wither and die.
 
Conditions for Disease Development:
 
The disease develops quickly under favorable conditions (dense plant growth and low light intensity).
   
High nitrogen fertilization, cool night temperatures, high relative humidity increase disease incidence and severity. Once the weather warms up, the plants tend to be able to outgrow the problem.
   
The optimum temperature for disease development is 20-27°C; Under field conditions, the disease stops at high temperatures (38°C and above).
   
The time between infection and symptom appearance is 3-7 days, in which large number of spores/conidia are produced.
   
Management and Control:
 
Use resistant varieties, if available.
   
Avoid planting in low, shady areas or increase light intensity in the area.
   
Provide good air circulation to minimize disease incidence and severity.
   
Avoid excessive use of N fertilizer or use a slow-release fertilizer.
   
Remove volunteer crops and weed hosts that may serve as alternate hosts for the fungus.
   
Apply sulfur–based fungicides at the early sign of the disease.
   
When plants are susceptible, thorough application of protectant fungicides like azoxystrobin before the disease appears may be necessary.
   

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