Aphthona euphorbiae Schrank Large flax flea beetle

Infestations of this widely distributed flea beetle are associated mainly with flax and linseed. Small pits or notches are made in the cotyledons, hypocotyls, leaves and stems; the beetles can also feed on the germinating seeds before the cotyledons have emerged from the soil. Most damage occurs in April and early May, and attacks are particularly severe if seedling growth and, hence, crop establishment is retarded; in some cases whole crops may be lost. New adults, reared in the summer, attack the leaves and developing seed capsules of older plants; heavy infestations lead to stunting and distortion but are of lesser significance than spring attacks. Minor damage is also caused to the foliage of various other plants, including apple, beet, cereals and strawberry.

BIOLOGY

Adults hibernate in herbage in hedgerows and woodlands, and usually emerge in April but typically slightly later in the season than the flax flea beetle, Longitarsus parvulus (p. 144). They then feed on the leaves of various plants, and often cause damage to the seedlings of flax and linseed. After mating, eggs are laid in the soil at a depth of 5-10mm, close to the roots of host plants. The eggs hatch in approximately 2-3 weeks. The larvae then burrow into the roots of flax, linseed and weeds such as Euphorbia, Plantago, Sisymbrium officinale and Taraxacum officinale, where they feed for about 4 weeks. When fully grown, they escape back into the soil where they pupate, and new adults emerge approximately 9 days later. These new adults feed from mid-July to August and then seek overwintering sites. There is just one generation annually.

DESCRIPTION

Adult 1.5-2.0mm long, black with a blue or greenish metallic sheen; prothorax and elytra finely punctured; antennae yellowish-red, the apical five segments dusky; legs mainly yellowish-red (cf. flax flea beetle, Longitarsus parvulus, p. 144).

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