Agromyza megalopsis Hering
In parts of continental Europe (e.g. southern and western Germany), this species is a potentially serious pest of barley; extensive damage to spring crops has occurred and yield reductions
Fig. 258 Puparium of Scaptomyza ilava (x15).
have been reported. The yellowish-brown mines can occupy much, if not all, of the leaf tissue; this leads to extensive discoloration and death of foliage. This pest does not occur in the British Isles.
Adults occur mainly in May. Eggs are then deposited in the leaves of host plants, often up to 40 within each infested leaf. At first, larvae form narrow galleries, directed towards the leaf apex; they then turn downwards and continue feeding towards the base, the mines uniting so that the larvae eventually feed gregariously. Occupied mines occur mainly in June and July but there may be a partial second generation in the autumn. Pupation usually occurs on the ground but puparia are sometimes found within the mines.
Adult 2 mm long, mainly black; wings hyaline, 2.5-2.7 mm long. Larva up to 3 mm long, whitish-yellow; cephalopharyngeal skeleton with dorsal elements (dorsal cornu) (see Fig. 107) divided into two; posteror spiracles 3-pored and abutting. Puparium brown.
This insect is a potentially important pest of winter wheat; attacks also occur on barley, oats, rye and various grasses. Heavy infestations have occurred on winter wheat in southeastern England and in Scotland, where consequent yield reductions have been reported. Mined leaves are conspicuously blanched and frequently shrivel and die: infestations on cereal flag leaves are common and of particular significance.
Adults occur in June, and eggs are then deposited in the leaves of various members of the Poaceae. Larvae feed in June and July. Each forms an extensive mine up to 20 cm long. At first the larva excavates a narrow gallery, directed towards the leaf tip. Later, it mines towards the leaf base; the gallery then develops into a broad blotch. Fully fed larvae pupate externally on the ground. At least in some areas, there may be a second generation in the autumn.
Adult mainly brownish to black, with pale squamae; wings 2.5-3.1 mm long. Larva up to 3 mm long, whitish-yellow; cephalopharyngeal skeleton with dorsal elements (dorsal cornu) (see Fig. 107) divided into two; posterior spiracles 3-pored and located on relatively large, widely spaced processes.
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