Onion fly - Plant Pests

The onion fly is a 6 mm fly that resembles a common housefly.

recognize larvae onion fly — Larvae onion fly, photo: Rasbak - CC BY-SA 3.0

Onion fly (Delia antiqua) is a 6 mm large fly that resembles a common housefly. The 7 mm long white-yellow larvae bore into the base of the plant after hatching. The fly hibernates as a pupa in the soil. On lighter soils, the fly deposits more eggs than on heavy clay.

Where to find

Amaryllis family:
- Chives
- Spring onion
- Leeks
- Shallot
- Japanese bunching onion
- Onion

Control

Spraying with pyrethrum or nettle spray kills the larvae.

Prevention

Crop rotation keeps the onion fly away. An insect-proof mesh prevents the butterfly from laying eggs on the crop. Do not use fresh manure as it attracts flies.