Chlorops pumilionis Bjerkander Gout fly

Although locally common, this pest is not of major significance. Barley, rye, wheat and cultivated grasses such as meadow foxtail and timothy are attacked but infestations do not occur on oats; wild grasses, including Elytrigia repens, are also hosts. Larvae of the overwintering generation cause a characteristic swelling of the basal parts of infested shoots and tillers (the so-called 'gouty' symptom). Although sometimes locally extensive on barley and wheat crops sown before mid-October, effects on overall yield are insignificant. Larvae of the summer generation cause most damage to late-sown spring cereals; affected plants remain stunted and gouty. Where eggs are laid on more advanced plants, the ear may fail to emerge from its sheath; in such situations grain yields are reduced. In the British Isles, this pest is most abundant in southern and southwestern England.

BIOLOGY

Adults of the first generation occur in May and June. Eggs are then deposited singly on the upper surface of cereal leaves, usually no more than one per plant. The eggs hatch in approximately 10 days. The larvae bore into the centre of the main shoot to feed, and individuals become fully grown in about a month. Each then pupates in situ, and the adult fly emerges from the puparium a month or so later. Adults of the autumn generation occur from late July to early October. Their eggs are deposited on early-sown winter cereals, cereal volunteers and grasses, but usually not until September at the earliest. Larvae of the autumn generation feed slowly throughout the winter months and usually complete their development in March or April.

DESCRIPTION

Adult 4-5 mm long, mainly yellow, marked with dark brown dorsally; thorax with three dark, broad, longitudinal bars; scutellum bright yellow (Plate 8f). Egg 1 mm long, elongate-oval, white (Fig. 263); chorion with a distinctive hexagonal sculpturing. Larva up to 8 mm long, translucent, hyaline-whitish to creamish-white, broadly sausage-shaped (Plate 9a); sternal spatula black, clearly visible; posterior spiracles inconspicuous.

Fig. 263 Egg of gout fly, Chlorops pumilionis (x40).

Puparium 5-7 mm long, yellowish-brown, elongate, flattened (Plate 9b); posterior spiracles inconspicuous (Fig. 264).

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