Phorbia securis Tiensuu Latewheat shoot fly

This minor pest is associated mainly with spring and winter wheat, but will also breed on grasses. The larvae feed singly inside young plants, each causing yellowing, wilting and death of the centre shoot. Damage is rarely of significance and usually most evident on backward crops. In the British Isles, attacks are most often found in eastern England.


Adults are active in March and April. Eggs are then deposited singly beneath the outer edges of the leaf sheaths of young wheat plants. The eggs hatch a few days later. Each larva then burrows downwards into a leaf sheath, to form a spiral channel, before entering the central shoot. The larvae continue to feed within the shoots for 2-4 weeks. They then enter the soil to pupate, usually in late May or early June. Larvae are present, therefore, later in the season than those of the wheat bulb fly (Delia coarctata, p. 197). Individuals usually remain within the puparium until the following spring, although in favourable districts a second or at least a partial second generation may occur on wild grasses.


Adult up to 5 mm long, dark grey; legs black. Larva up to 7 mm long, yellowish-white; anterior spiracles prominent, frilly-edged, with up to 20 lobes; posterior spiracles borne on distinct tubercles; posterior papillae very small or absent (cf. wheat bulb fly, Delia coarctata, p. 197).

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