Purple Blotch in Onions : Causes & Control What is Purple Blotch? Purple Blotch is a fungal disease caused by Alternaria porri, affecting onion plants by Symptoms • Purple or brown spots on leaves • Yellowing and weakening of affected areas How it Spreads ? • Spores spread in wet, humid conditions • Crowded planting and poor air circulation increase risk Chemical Control for Purple Blotch in Onions : • Fungicides: Apply Chlorothalonil, Mancozeb, or Propiconazole at the first sign of infection. • Systemic Options: Use Tebuconazole or Azoxystrobin for long-lasting protection. • Rotation: Rotate fungicides to avoid resistance and ensure thorough coverage on all plant parts. • Reapplication: Reapply every 7-14 days, based on weather and product guidelines.