This species is a locally common but minor pest of potato; it is also associated with weeds such as Solarium dulcamara and S. nigrum. Larvae mine within the roots, but most noticeable damage is caused by newly emerged adults which graze on the foliage during the late summer and early autumn before hibernating.
Adult beetles emerge from hibernation in May but sometimes earlier. Eggs are laid in June, either placed singly or in small groups just below soil level, close to host plants. They hatch about a week later. The larvae attack the softer parts of roots and feed for about a month before pupating. New adults emerge about a month later; they feed on the foliage of Solanaceae and then hibernate. There is just one generation annually.
Adult 2-3 mm long, reddish-brown to pale yellowish-brown with the underside of the body, femora and elytral suture black; antennae 10-segmented (Fig. 220b). Egg 0.6-0.7mm long, elongate-oval, yellowish-white. Larva up to
6 mm long; body whitish; head, prothoracic plate and anal plate pale brown.
Psylliodes chrysocephala (L.) Cabbage stem flea beetle
The cabbage stem flea beetle is a locally common pest of winter oilseed rape; infestations may also occur on overwintering vegetable brassicas. The adults bite out irregular holes in the leaves but such damage is usually unimportant unless plants are small and growth is slow. Larval infestations of stems, petioles and growing points are usually more serious, and damaged tissue typically rots and turns brown; larval-damaged plants are also particularly liable to infection by canker (Leptosphaeria maculans). Larval damage to growing points causes discoloration and distortion. Heavily infested plants are weakened, stunted, malformed and, sometimes, multi-stemmed (Plate 4f); if small, plants may wilt and die. Light attacks, although not always significant on older plants, can reduce the size of heads of autumn cauliflowers. Adults may be brought into store with harvested rape-seed; however, they do not cause damage and do not constitute a storage problem, as they soon disperse.
Young adults are often abundant during July, following their emergence from the pupal stage, and may often be found in vast numbers amongst harvested rape-seed being carried away from fields in trailers. They remain active at or near emergence sites for 2-3 weeks but then aestivate, to reappear in September. They then migrate to new host plants, where they feed and mature. Eggs (up to 150 per female) are then laid in the soil close to brassica plants, mainly from September to November but sometimes later. Most eggs hatch from early October to December, but cold weather can delay hatching until the late winter or early spring. Young larvae invade the petioles from above and also enter the stems, boring into the tissue and feeding gregariously within the pith; at intervals, they break through the epidermis so their galleries remain partly open; growing points may also be attacked. Larvae feed throughout the winter and early spring, passing through three instars. When fully grown, they enter soil and pupate; adults appear
in the early summer. There is just one generation annually.
Adult 4-5 mm long, metallic bluish-green to metallic greenish-black, but sometimes bronzy (Fig. 222); antennae 10-segmented (see Fig. 220b) (cf. Phyllotreta spp., Fig. 220a). Egg 0.5 mm long, elongate-oval, yellowish to yellowish-orange. Larva up to 8 mm long; body whitish; head, prothoracic plate, anal plate and pinacula black; thoracic legs well developed (Fig. 223) (cf. cabbage leaf miner, Phytomyza rufipes, p. 192; cabbage stem weevil, Ceutorhynchus pallidactylus, p. 156; Scaptomyza flava p. 185). Pupa 5 mm long, white.
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