Invasive Species Compendium

Detailed coverage of invasive species threatening livelihoods and the environment worldwide

Abstract

Infestations by Metcalfa pruinosa in the Venice district.

Abstract

Metcalfa pruinosa, a North American flatid first recorded in Italy in 1980, is becoming widespread in the north-east, especially near Venice, and its life cycle, food-plants, economic importance, regulating factors and control are reviewed. Although primary concern is for grapevines and fruit trees such as fig, lemon, apple, pear, plum and peach, shrubs and forest trees are also attacked, and tree-lined roads appear to be a means of spreading from one area to another. M. pruinosa has 1 generation a year and overwinters in the egg stage under tree bark; the first nymphs are found on the leaves and stems in May. Adults are present from July to October. Dense populations of nymphs cause stunting of the shoots, while those of adults produce large quantities of honeydew on which sooty mould develops. Mould damage is common in gardens but has also increasingly been observed in vineyards. Chemical control against dense nymphal populations might be justified on valuable trees, but control of sooty mould by means of fungicides is usually more useful. Chemical control of adults is difficult owing to their mobility and long life.