Common Onion Diseases in Kenya and How to Treat Them Effectively
Posted on June 26, 2025
1. Purple Blotch
Purple blotch appears as small, water-soaked lesions on leaves that turn purplish-brown with yellow halos.
Cause: Fungus (Alternaria porri)
Treatment: Use fungicides like Dithane M-45 or Score 250EC. Ensure proper spacing to reduce humidity.
2. Downy Mildew
This shows as pale yellow spots on upper leaves and grey mold underneath. It thrives in cold, wet weather.
Cause: Peronospora destructor (a water mold)
Treatment: Spray with Ridomil Gold or Milraz. Improve drainage and avoid overhead irrigation.
3. Fusarium Basal Rot
This affects the bulb base, leading to yellowing and rotting from the bottom.
Cause: Soil-borne fungus (Fusarium oxysporum)
Treatment: Practice crop rotation. Apply Trichoderma-based bio-fungicides or Folicur.
4. Onion Smut
Characterized by dark, elongated lesions on seedlings which eventually wilt.
Cause: Urocystis cepulae
Treatment: Use treated seeds and apply Thiram before planting. Avoid planting in infected fields for 3 seasons.
5. Bacterial Soft Rot
Bulbs become watery and emit foul odor. Common during storage.
Cause: Bacteria (Erwinia spp.)
Treatment: Avoid injury during harvest. Ensure bulbs are fully dry before storing.
6. Anthracnose
Small black spots appear on leaves, enlarging quickly in humid weather.
Cause: Colletotrichum spp.
Treatment: Use preventive sprays like Ortiva and rotate with Score or Copper-based fungicides.
General Prevention Tips:
✅ Avoid waterlogging and overcrowding
✅ Always sanitize tools and equipment
✅ Do soil testing before planting
✅ Purchase certified seeds and agrochemicals from trusted suppliers
Need Help? Visit Farmers Centre Ltd today for expert advice and trusted crop protection products.
📞 Call/WhatsApp: 0110089926