Phyllotreta nemorum L Large striped flea beetle

This flea beetle is a common pest of vegetable brassica crops, especially radish and turnip; brassicaceous ornamentals, such as wallflower, are also attacked. Adults cause a pitting of cotyledons and leaves, and the larvae form small, pale, linear to blister-like leaf mines that eventually dry out. Attacks are most serious on young plants, especially in hot, dry weather when growth is retarded by lack of moisture. Larvae are unable to penetrate into heavily waxed plants such as cabbage, cauliflower, rape and swede.

BIOLOGY

Adults occur from April onwards, and eggs are laid on the surface tissue of host plants or in the

Fig. 221 Large striped flea beetle, Phyllotreta nemorum (xl8).

soil, typically in batches of three or four. The eggs hatch in 8-10 days, and the larvae immediately burrow into the leaves to feed. On suitable hosts, they mine within the leaves, petioles and stems for 2-3 weeks; they then enter the soil to pupate in earthen cells. Adults appear about 2 weeks later, usually in July. The young adults enter hibernation in September, hiding away in debris and litter. There is just one generation annually.

DESCRIPTION

Adult 2.5-3.0mm long, black with a pair of widely spaced, sinuous, yellow bands on the elytra, the black area between them widening both anteriorly and posteriorly (Fig. 221); tibiae reddish-yellow (cf. Phyllotreta undulata, p. 148). Egg yellow, spherical. Larva up to 6mm long; body elongate and yellowish, with blackish plates on the thorax; head blackish.

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