Viteus vitifoliae Fitch Grape phylloxera

This notorious pest was introduced into Europe from North America in the mid-nineteenth century. The pest destroys the young roots of grape vines and also produces extensive callusing of the older roots. European grape vines are especially susceptible to attack and their complete destruction is possible unless they are grafted onto phylloxera-resistant rootstock. The pest can also produce greenish or reddish, wart-like galls on the underside of leaves (cf. galls formed by the grape erineum mite, Colomerus vitis, p. 258) but these are of little or no direct significance.

BIOLOGY

In Europe, this pest persists as radicicolae (which breed asexually on the roots of grape vines), each female laying eggs which normally give rise to nymphs that develop into further radicicolae. There are several such generations annually. Occasionally, eggs laid by radicicolae produce nymphs that, instead of becoming radicicolae, invade the aerial parts of the plant and develop into gallicolae. These gallicolae feed and breed within distinctive leaf galls. Nymphs emerging from their eggs either continue to develop in leaf galls as gallicolae or disperse to the roots, where they will develop into radicicolae. Although there is a sexual phase in the life-cycle, this very rarely occurs in Europe.

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