Cydia nigricana F Pea moth

This widely distributed species is an important pest of cultivated peas. The larvae bore into the developing seeds (Plate 12e), and heavy infestations cause considerable losses to field crops and to garden peas. The insect also attacks other cultivated and wild Fabaceae. The extent of damage within infested pods tends to be greatest in dry-harvested peas, as these are harvested later in the season, but significant damage rarely occurs in early-sown peas due to be harvested before July.

BIOLOGY

Moths occur from late May or early June onwards, but are usually most numerous during mid-July. They often congregate in suitable habitats, and fly during the afternoon in warm, sunny weather and in the evening. Eggs are laid mainly on the underside of expanded leaves and stipules of host plants, either singly or in small groups; they are usually deposited on the upper half of the plant and hatch about 8 days later. The young larvae are very active and each crawls rapidly over the host plant before locating a pod and burrowing inside to attack the seeds. Each larva feeds for several weeks and passes through five instars. When fully grown, usually in August or September, the larvae escape into the soil. Here they overwinter, each in an oval (c. 10 x 4.5 mm), thick-walled, silken cocoon incorporating particles of soil. Most cocoons are formed a few centimetres below the surface but some occur at much greater depths. In the following spring, earlier or later depending on temperature, larvae (but not necessarily all of those already close to the surface) emerge from the cocoons and move through the soil to spin feeble, web-like struc tures just below the surface. The larvae then pupate, and adult moths emerge about 2 weeks later. There is just one generation annually.

DESCRIPTION

Adult 12-16 mm wingspan; forewings mainly dark brown, suffused with grey, and marked with several black dashes below the apex of the costa and with several oblique whitish strigulae along the costal margin, especially towards the tip (Plate 12f); hindwings dark brown. Egg 0.7 x 0.5 mm, flattened and oval; yellowish-white when newly laid but each soon develops a pair of irregular pinkish-red markings that disappear before hatching. Larva up to 14 mm long; body yellowish-white, often greenish-tinged; pinacula greyish (Plate 12e); head yellowish-brown; prothoracic plate pale yellowish-brown, marked with dark brown or blackish; anal comb absent. Pupa 7-8 mm long, dark brown.

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