Saperda carcharias (large poplar borer)

Ovipositions are revealed by vertical incisions in the bark of about 5 mm in length, which on young trees are confined to the base of the trunk. When plants grow vigorously, the cut may become convex and the wound can open or gape. Only one egg can be found in each incision.Initial larval activity is revealed on the trunk by a thin, brownish frass which in a short time becomes progressively coarser and whiter. When the larva grows older and penetrates into the trunk sap exudes from the wound.Adult feeding activity is revealed by characteristic holes in the leaf, which can be circular, oval, elongate or irregular but never reach the margin of the leaf. Moreover, the serration caused by the large biting mandibles is always distinct.

Chemical protection is carried out in poplar plantations when high-quality wood for industry has to be obtained. Particular attention has to be paid to older trees, where lower vigour from age or competition can decrease the plant's reactive capacity and consequently allow higher survival of the first developmental stages of the pest.Treatments are generally directed towards the larvae, which are the most vulnerable stage. The young larvae can be killed soon after hatching by spraying trunks with organophosphate or pyrethroid insecticides; very high mortalities can be achieved when the larvae are still feeding on bark tissues and before they penetrate into the wood (De Bellis, 1958; De Bellis and Cavalcaselle, 1963; Lapietra and Allegro, 1982, 1984; Allegro, 1988a, 1998). On young trees the larvae are only found at the base of the trunk, thus limiting the portion to be treated. Spraying the trees in the first year of the plantation cycle is unnecessary, as the eggs laid at the base of the trunk in the nursery will die at transplanting (the plantlet base is placed about 1 m deep in the ground). Chemical control can significantly increase the mortality of the egg parasitoid Euderus caudatus (Arru, 1970, 1972).Once the larvae are deep in the wood, only localized treatments are effective; they can be carried out by injecting insecticides at high concentration directly into the gallery, in liquid (Vasic, 1959) or aerosol formulation (Lapietra, 1980). This strategy causes little harm to natural enemies.The control of adults has also been tested (Dafauce, 1965, 1966) but it is not as effective as the control of larvae and is not recommended due to its heavy environmental impact.A mechanical method of control based on plugging the exit holes of the larval galleries by concrete has been tested (Turcek, 1954). Physical barriers have also been tested in order to prevent climbing of adults on the trunks (Allegro, 1990). Particularly effective results were achieved using barriers made of Algoflon D60 (an aqueous dispersion of polytetrafluoroethylene (teflon)) applied to the basal metre of the stem.

S. carcharias is considered to be an economically important pest in Italy, France, Spain, Netherlands, Belgium, Austria, Hungary and Romania (Nef and Menu, 1994). It is mostly injurious in countries where poplars are grown with the aim of producing high-quality wood, mainly for the plywood and furniture industries (Italy, Spain, France, Hungary). In Italy it has been estimated that, in 1996, 8% of poplar trees in artificial plantations were damaged by S. carcharias (together with Cossus cossus) and about 350,000 Euros were spent by poplar growers on the purchase of insecticides (Allegro, 1998).