Pest Information

Common names: Onion fly
Scientific name: Delia antiqua
Diptera:Anthomyiidae

Synonyms: Onion maggot

Host plants

Onion, shallot, and leek

Distribution

Asia, Africa, Europe, USA

Damage

The larva eats the lateral roots, then tunnels into the taproot, and sometimes bores into the base of the stem. Attacked plants wilt and the leaves turn bluish. The plants become stunted or eventually die.

Description

The eggs are dull white, elongated, longitudinally striped, and about 1.5 mm in length. They are laid singly or in groups of 15-20 near the host plant, often on the neck or sometimes at the leaf's axil or between the scales of the bulb.

The larva is white and about 8 mm in size. The larva penetrates the tissue between the leaf shoots or at the base of the roots and feeds on the decomposing tissues. It occurs especially on seedlings of onion and leek, on thinned-out onions and on shallots. A larva can attack several seedlings in succession that cause wilting and eventual death of plants.

The pupa is light to dark-brown in color, is ringed and ovoid, and about 7 mm in length. Pupa is found in the soil near the base of the plant.

The adult fly is yellowish-gray in color with yellowish wings, black legs and antennae. It is about 6-7 mm long. An adult female fly is seldom found in the host plant. It flies to the plant only to lay its eggs.