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

IPM OF CITRUS PESTS IN GREECE
43
individuals/leaf respectively. As a final point the citrus leafminer causes problems
particularly on young citrus trees and overgraftings in nurseries but its damage on
adult trees under Mediterranean conditions lacks economic importance (Garcia-Marí,
Granda, Zaragoza, & Agusti, 2002).
2.4.1. Sampling and Monitoring
Sampling for monitoring infestation by the citrus leafminer involves collection of
new shoots and leaves from growth flushes and observation of mines. The
economic threshold for a chemical application on citrus leafminer has been
estimated by several researchers; in China it is 0.74 larvae/leaf (or percentage of
leaf damage over 20%) (Huang & Li, 1989); in Australia it is fixed at 25% of
shoots with leaves smaller than 3 cm exhibiting mines of L1 (Beattie & Smith,
1993); in Florida it is set at 30% of young shoots baring mines with live larvae
(sampling should be performed when half of the trees in the orchard have young
shoots) (Knapp et al., 1995).
2.4.2. Biological Control
Five exotic hymenopteran parasitoid species were introduced from Cyprus in 1996
and were subsequently mass reared in the insectary of the Institute of Subtropical
Crops and Olive (National Agricultural Research Foundation) in Chania-Crete. The
introduced species were the encyrtid Ageniaspis citricola Logvinovskaya
(Hymenoptera: Encyrtidae) and the eulophids Cirrospilus quadristriatus (Subba
Rao and Ramamani), Citrostichus phyllocnistoides (Narayanan), Quadrastichus sp.
and Semielacher petiolatus (Girault) (Hymenoptera: Eulophidae). A small number
of all parasitoids were released in 1996 but cultures of Ageniaspis citricola and
Cirrospilus quadristriatus could not be kept after the first year and hence these
species did not establish (Kalaitzaki, 2004).
Citrostichus phyllocnistoides, Quadrastichus sp. and Semielacher petiolatus were
released systematically (100–250 individuals/species/10 days from June to November)
in orange and mandarin orchards in Crete (Chania) and the impact of both native and
introduced parasitoids was studied from 1997 to 1999. Similar releases were also
performed in Peloponnese (Argolis, Korinthia, Lakonia) (Tsagarakis et al., 1999).
All of the released parasitoid species established in Crete and contributed to the
reduction of the citrus leafminer population, especially Citrostichus
phyllocnistoides which dispersed very rapidely and far from the release sites and it
achieved the highest percentage parasitism (mean 15.2–20.8% and maximum 45.8–
51.1% on mandarin and orange trees, respectively).
Only a few native parasitoid species were found to parasitize the citrus leafminer in
Crete i.e. Pnigalio pectinicornis L., Neochrysocharis formosa (Westwood) and
Cirrospilus pictus (Nees) (all Hymenoptera: Eulophidae) in very small numbers and
with small contribution in percentage parasitism of the citrus leafminer (Kalaitzaki,
Lykouressis, & Michelakis 1999; Kalaitzaki, 2004). Among them, P. pectinicornis was
the most abundant one (Kalaitzaki et al., 1999; Kalaitzaki, Lykouressis, Perdikis, &