Mayetiola destructor Say Hessian fly

The hessian fly is associated mainly with wheat but will attack barley and rye; Elytrigia repens is also a host. The larvae produce a noticeable swelling at the base of young plants; later, they also cause the leaf nodes to swell. The ears of infested plants may turn whitish and the grains often shrivel; infested plants may also lodge or break off in the wind, and this contributes to further yield loss. Although of relatively little importance in the British Isles, hessian fly is a major pest in many other wheat-growing countries, particularly North America.

Fig. 248 Puparium of hessian fly, Mayetiola destructor (x!5).

Fig. 248 Puparium of hessian fly, Mayetiola destructor (x!5).

BIOLOGY

Adults of the first generation appear in March or April. Eggs are deposited in batches on the leaves of host plants, and they hatch about a week later. The larvae feed within the shelter of leaf sheaths at the base of the plant and complete their development in approximately 3 weeks. They then pupate in situ to form a cluster of seed-like puparia (this is the so-called 'flax-seed' stage) (Plate 6d). Adult midges appear about 3 weeks later, but development times vary considerably according to temperature. There is usually at least one further generation, or partial generation; puparia form the overwintering stage.

DESCRIPTION

Adult black with a brownish or brownish-red abdomen (Fig. 247). Egg 0.5 mm long, sausage-shaped, red. Larva up to 4 mm long, whitish, translucent; sternal spatula robust, with a bifid tip. Puparium 4 mm long, dark brown, resembling a seed of flax (Fig. 248).

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