Fact sheet

Exotic threats of : antiqua –

What is it? The onion fly (Delia antiqua) is a major pest of species, specifically onions, and , and can be very difficult to control once established.

The fly, under normal conditions, produces two generations in a year. The generation appearing in spring can be especially harmful to crops, affecting seedlings of onion and , thinned out onions and shallots. The fly causes wilting and death in seedlings and young plants and induces rotting in mature plants, attracting further Diptera Adult Delia antiqua (dorsal view) species. detected on imports. Image Simon Hinkley & Ken Walker, Museum Victoria, Pest & Diseases Imape Library (PaDIL), What do I look for? www.padil.gov.au. Adults: 6 to 7 mm long, yellowish grey with 5 dark stripes on the thorax, yellowish wings, black legs and antennae, similar in appearance to a large domestic fly.

Eggs: dull white, elongated and longitudinally striped, measure 1.5 mm in length.

Larvae: a white maggot which reaches 8 mm when its development is complete.

The larvae penetrate the host through the base of the leaf shoots or roots, and feed on the decomposing tissue. Early symptoms of D. antiqua presence show as yellowing and wilting of the host’s outer leaves. Green and apparently healthy leaves will become flaccid, and the whole plant may collapse. Later generations of larvae tunnel into the onion bulbs as well as attack the roots.

Both the fly and larvae do not have any distinct features which allow for its easy identification, therefore suspect samples must be Adult Delia antiqua (lateral view) identified by an expert. detected on garlic imports. Image Simon Hinkley & Ken Walker, Museum Victoria, Pest & Diseases Imape Library (PaDIL), www.padil.gov.au.

Where is it found? It is found in many major agricultural areas throughout the world, these include Europe, UK, Asia, USA, and Canada.

Reporting Growers may report suspected exotic pests to the Exotic Plant Pest Hotline (1800 084 881) or can directly contact their relevant state agriculture or primary industries department.

To minimise the risk of disease or pest spread, samples should not be moved until they have been checked by an expert.

This fact sheet is part of the National Onion Industry Biosecurity Plan. For more information about the Biosecurity Plan, please contact Plant Health Australia.

FOR MORE INFORMATION Contact Plant Health Australia

Phone: +61 2 6260 4322 Fax: +61 2 6260 4321 www.planthealthaustralia.com.au

ABN 97 092 607 997

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