[Edited_by_A._Ciancio,_C.N.R.,_Bari,_Italy_and_K.(Bookos.org)

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L. ZAPPALÀ
Vivas, 1995; Argov, Rössler, & Rosen, 1995), the incidence of the first one on the
parasitization has reached 80–90% (Caleca et al., 1998; Caleca & Lo Verde, 1998;
Conti et al., 2001). Moreover, the following species have been occasionally detected
in Sicily: Apotetrastichus postmarginalis (Bouček), A. sericothorax (Szelényi),
Asecodes delucchii (Bouček), A. erxias (Walker), Neochrysocharis formosa
(Westwood) and Ratzeburgiola incompleta Bouček. Finally, other eulophids have
been rarely recovered: Aprostocetus spp., Baryscapus sp., Chrysocharis pentheus
(Walker), Cirrospilus diallus Walker, C. nr. lyncus (Nees), C. vittatus Walker,
Diglyphus isaea (Walker) and Pnigalio soemius (Walker) (Viggiani & Giorgini,
1995; Benfatto, 1996; Caleca, Lo Verde, & Massa, 1996; Liotta, Peri, Salerno, Di
Cristina, & Manzella, 1996; Caleca et al., 1998; Caleca & Lo Verde, 1998; Giorgini
et al., 1998; Lo Pinto & Salerno, 1998; Mineo, 1999; Conti et al., 2001).
Starting from 1999 to 2002 the exotic eulophids C. phyllocnistoides and
S. petiolatus have progressively substituted almost all the indigenous parasitoids
previously detected on P. citrella, inducing a decrease of their parasitism to less than
one third of what had been recorded, up to 1998.
The high degree of specificity reached by P. citrella parasitic complex represents
an important element in the biological control of this pest. The data collected in the
main Italian citrus growing areas from 1996 up to now reveal an activity of the
parasitoids (including both parasitization and host feeding) that has grown from 32%
(1996–1998) up to 65% in more recent years (Siscaro & Reina, 2005), mainly
thanks to the biocontrol activity of the 2 exotic eulophids S. petiolatus and C.
phyllocnistoides. These species permanently established in Sicilian citrus groves
showing a contribution of 90% to the total parasitization (Siscaro, Caleca, Reina,
Rizzo, & Zappalà, 2003). Besides, a seasonal alternation in their activity was
highlighted: S. petiolatus parasitization is in fact mainly concentrated in the first
months of CLM infestation (June–August), while C. phyllocnistoides activity is
more intense in the second part of the season (September–October) (Siscaro et al.,
2003).
The establishment of the introduced eulophids is most likely related to the
presence of alternative hosts (Massa et al., 2001; Massa & Rizzo, 2001; Lo Duca et
al., 2002), and their seasonal alternation could be partly explained by the different
biological and ecological attitudes the two species showed on hosts of native flora
(Rizzo, 2003). Therefore it is important to maintain a rich biodiversity in citrus
groves in order to provide alternative food and shelter to CLM parasitoids, mainly in
winter and spring, when CLM populations are at their minimum levels.
Biological control, together with cultural techniques based on reducing irrigation
and fertilization with the aim of containing excessive vegetation, has proved
effective in containing P. citrella infestations in adult citrus orchards. The situation
is different on young and re-grafted trees, as well as in nurseries where damage
caused by the leafminer may be more serious. In these cases chemical treatments can
be applied using cytotropic or systemic insecticides, or insect growth regulators
which, for their mode of action, should be employed sooner than the previous
compounds. Mineral oils also have a repellent action on egglaying females and a
reduced impact on the ecosystem. They can be used at a dose of 0.5–1 l/hl which
protects the plants for 6–10 days, without rain, and the treatments must be applied