The vine mealybug, Planococcus ficus (Signoret), and the citrus mealybug, Planococcus citri (Risso), are currently the most economically important pseudococcids in vineyards in Italy (Dalla Montà et al., 2001). Pl. ficus is also considered to be a key pest in many other countries (Ben-Dov, 1994). The two species cause severe damage to the host plant, and significantly reduce the crop due to the production of honeydew, which allows the growth of sooty molds, and to their potential as virus vectors. The vine mealybug, in particular, is known to transmit grapevine leafroll and corky-bark diseases (Engelbrecht & Kasdorf, 1990; Tanne et al., 1989). Populations of these two sibling species may coexist apparently without mutual interference (Rotundo & Tremblay, 1982), but some differences occur on their relationships with parasitoids. For instance, Pl. citri is successfully controlled by Leptomastix dactylopii Howard (Hymenoptera Encyrtidae) but this parasitic wasp is ineffective in controlling Pl. ficus, whereas Anagyrus pseudococci (Girault) (Hymenoptera Encyrtidae) can be employed in biological control programs for both mealybugs (Abdelkhalek et al., 1998; Mendel et al., 1999). Therefore, a well-timed identification of pests is very important for choosing the most suitable biocontrol agents for IPM. The two scale insects are similar morphologically and their taxonomic separation is based on the distribution and presence of multilocular pores and tubular ducts on the adult females and these are difficult to detect (Cox & Ben-Dov, 1986; Williams & Granara de Willink, 1992). Therefore the discrimination between these two species needs a simple
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