Causal Agent: 

Fungi (Colletotrichum gloeosporioides; Gibberella moniliformis spp.)

 

Characteristic Symptoms:
 
Affected leaves initially have small white sunken spots and eventually form a concentric ring pattern covered with orange spore mass.
   
Affected plants exhibit  yellowing and twisting of leaves.
   
Neck becomes elongated and bulb size is reduced.
   
Conditions for Disease Development:
 
The pathogen is soil-borne and survives on plant debris for long periods of time.
   
The disease is severe with prolonged humid conditions.
   
Spores are disseminated by wind and rain splashes.
   
Diseased plants are source of secondary inoculum, which spreads from plant to plant in the field.
   
Wounding/bruising predisposes plants to infection.
   
Management and Control:
 
Use pathogen-free seed.
   
Remove and destroy infected plants as soon as symptoms are observed to minimize spread of disease.
   
Avoid prolonged moisture to minimize disease severity.
   
Avoid wounding/injuries as this may predispose plants to infection.
   
Crop rotation for 2-3 years may help reduce inoculum level in the soil.
   
Drench nursery beds with fungicides like  promocarb hydrochloride (e.g. ProplantⓇ, PrevicureⓇ) or fosetyl aluminum (e.g. AlietteⓇ), metalaxyl+mancozeb (e.g. Ridomil Gold MZ 68 WGⓇ, Apron XL 350 ESⓇ), mancozeb (e.g. Attain M-80Ⓡ, Achem Mancozeb 80 WPⓇ, Micron 80 WOⓇ, VanzebⓇ) to minimize incidence and prevent introduction of disease to the field. 
   
Spray with difenoconazole (e.g. ScoreⓇ, MontanaⓇ, PursueⓇ, BashⓇ), difenoconazole+proficonazole (e.g. ArmureⓇ), Pyraclostrobin (e.g. Cabrio 25 ECⓇ),  Bacillus subtilis strain QST 713 (e.g. Serenade®, Virtuoso®) and azoxystrobin (Amistar®, MiradorⓇ, RobatoⓇ) at the early onset of the disease to prevent further development and spread of the disease.

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