Identifying and Preventing Leek Rot Caused by Onion Maggots

Introduction

Leeks rotting from the top down in late summer often indicate onion maggot infestation.

Symptoms of Onion Maggot Damage

Maggots attack at the base of leaves, causing top-down rot. Grubs typically damage roots. Both pupate in soil.

Prevention Strategies

• Remove all infected plants from the garden (composting is okay).
• Dust around bulbs in spring with diatomaceous earth or wood ashes.
• Rotate crops—avoid planting alliums where radishes or other hosts grew.

Conclusion

Sanitation, spring dusting, and crop rotation break the onion maggot cycle and protect leeks.