WSU Extension


Onions, Garlic
Basal rot 
Downy mildew 
Gray mold 
Neck rot 
White rot 
Onion maggot 
Onion thrips 

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Caption: Onion basal rot in early season
Photo by: L.J. du Toit
Onions, Garlic : Basal rot
(revision date: 6/3/2014)

Basal rots of onion, garlic, and related species are caused by fungi. Affected plants are yellowed, wilted, and grow poorly. Reddish discoloration may be present on affected garlic, while onions may show a red-brown rot beginning where roots are attached to the bulb at the basal plate. Initial infection typically occurs on the roots or the basal plate. The rot progresses upward through the bulb and can also occur in stored infected bulbs when sufficient moisture is present. Plants attacked by onion maggots or other insects are more likely to be infected.
Management Options

Non-Chemical Management
  • Plant tolerant onion cultivars such as 'Bronze Reserve', 'Cashe', 'Cima', 'Golden Cascade', 'North Star', 'Oro Grande', 'Sassy Brassy', 'Sentinel', and 'Valient'.
  • Control insects and prevent root damage such as that caused by overfertilization.
  • Rotate crops. Do not plant onions or related crops in the same locations each year.
  • Plant in well-drained soils.
  • Dry bulbs before storing. Store bulbs in cool, dry, well-ventilated locations.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Onion basal rot in early season
Photo by: L.J. du Toit
Caption: Onion basal rot symptoms on foliage
Photo by: L.J. du Toit