It has a wingspan of about 12mm, and is brown with dark patches and a white crescent. Although it has the potential to be a pest, it is far too scarce to be of any damage, but in Europe where it is abundant it is a serious pest.
As it's name suggests, it's larvea feed on leek, onion and chive. It is found mostly on the South-East, especially by the coast. It flies in two generations, June-July, and then from October through the Winter to the Spring.
This species was classed as a Red Data Book species, but is now classed as local in Britain, as they have spread so quickly, and in some southern counties it is now a pest.