Onion white rot
Disease A soil fungus that rots the roots and bulbs of onions, garlic and leeks.
What to look for
Yellowing, wilting leaves and a fluffy white mould at the base of the bulb, with tiny black dots (sclerotia) that can survive in soil for 15 to 20 years.
When: Spring to autumn, especially in cool conditions.
How to prevent it
- Buy clean, certified sets and cloves.
- Clean tools and boots to avoid spreading infected soil.
- Never move soil or compost from affected beds.
How to deal with it
- Lift and bin infected plants, including all soil around the roots.
- Do not grow alliums on infected ground again, and grow them in containers of fresh compost or a new bed instead.
Crops it affects
If you choose to use any treatment, use only products approved for UK home gardens, follow the label and avoid spraying open flowers. See all pests and diseases.