Onion fly

Symtpoms
Young plants wilt and die, and older plants soften and rot. Most damage is in mid-summer, but can occur in other growing months too. Can be confused with stem eelworm.

Spot them
Onion fly looks like a small grey house fly. Its eggs are laid in the spring and early summer, near the base of the leek or onion, on the leaves and in the soil nearby. The maggots are white and about half an inch (1.25 cm) long when fully grown.