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

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F. KARAMAOUNA ET AL.
2.4. The Citrus Leafminer, Phyllocnistis citrella
The citrus leafminer Phyllocnistis citrella was first recorded in Greece on the island
of Rhodes (southeastern Greece) and in Crete in June 1995 (Anagnou-Vernoniki,
1995; Michelakis & Vacante, 1997). More recordings of the pest followed on other
Greek islands (Cos, Astipalea, Lesvos, Chios, Samos and Paros) and in the
mainland (Attica and Laconia-Peloponnese) in July and August, 1995 (Anagnou-
Vernoniki, 1995). After a few months the citrus leafminer was found in almost all
citrus growing areas of Greece (Tsagarakis, Kalaitzaki, Lykouressis, Michelakis, &
Alexandrakis, 1999).
Upon introduction of the pest, quarantine and other regulatory measures were
enforced but they had a very limited impact on the spread of the pest which very
rapidly invaded all citrus cultivated areas in the state. The growers were advised
not to overuse and/or misuse insecticides as experience from other countries had
shown that the chemical control was a short term and expensive solution due to the
long vegetative period of citrus and the large number of generations of citrus
leafminer per year. Furthermore, chemicals would have unfavorable side effects on
the existing effective biological control of other citrus pests and there was a
possibility of resistance development of the citrus leafminer to insecticides.
Nevertheless, many growers tried to apply insecticides but soon they had to
admit that chemicals were an inadequate solution to the problem. Moreover,
chemical control using broad spectrum insecticides was indeed putting at risk the
Integrated Pest Management of citrus insect pests, such as scales and aphids as
well as the successful biological control of the woolly whitefly Aleurothrixus
floccosus by disruption of the newly established exotic parasitoid Cales noacki.
Biological control, on the other hand, was known to be the most effective method
of managing the citrus leafminer in commercial orchards (Hoy et al., 1995; Neale,
Smith, Beattie, & Miles, 1995; Smith & Beattie, 1996; Argov & Rössler, 1996).
Therefore the impact of the native natural enemies was studied and classical
biological control by introduction and release of the most promising parasitoid
species in two sites (Crete and Peloponnese) was attempted (Kalaitzaki, 2004). In
addition cultural measures to prevent dispersal were strongly recommended by the
agronomists/consultants to the citrus growers (Michelakis & Vacante, 1997).
Early studies after the implementation of the classical biological control
programme of the citrus leafminer in Crete showed that the number of immature
individuals of the citrus leafminer/leaf fluctuated from 0.1–3.9 to 0.01–1.06 on
orange trees and mandarin trees, respectively (with mandarin being more resistant to
infestation) (Kalaitzaki, 2004). Five peaks of the live immature individuals of the
citrus leafminer/leaf were recorded on orange trees (two in summer: end of May and
mid June and three in autumn: end of September, end of October and mid November)
and four peaks on mandarin trees (mid June, end of September, end of October,
beginning of December) (Kalaitzaki, 2004). Lower levels of infestation (0.017–1.76
live immature individuals/per leaf) were recorded in Argolis-Peloponnese, the second
area of the parasitoids’ release (Tsagarakis et al., 1999). Later studies (2004 and
2005) on the islands of Lesvos and Chios and in western mainland revealed low
infestation of the citrus leafminer i.e. 0.06–0.58, 0.08–0.72 and 0.04–0.82 immature