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F. KARAMAOUNA ET AL.
However, escharotic fruits due to the feeding of the Kelly’s citrus thrips reached
70% of the total produce in Chania-Crete and they were rejected for export during
the selection process at packaging in 2001 (Varikou, 2006). Baker et al. (2005)
refer that feeding of Kelly’s citrus thrips on young and mature fruit causes scarring
(halo), marking and rind bleaching which typically encircles the apex of the fruit in
the immediate vicinity of the calyx.
Heliothrips haemorrhoidalis is a polyphagous parthenogenetic species which can
complete six generations on citron and overwinters as an adult on citrus trees and
on poaceous weeds. This is the reason why weed control by ploughing, in
February, was recommended together with chemical applications in March by
Anagnostopoulos (1939).
The Kelly’s citrus thrips P. kellyanus is arrhenotokous (Varikou, 2006) and is
not known to breed on any indigenous plant species of the Mediterranean region
except Citrus sp. (Webster, Cooper, & Mound, 2005a). However, P. kellyanus
can use the pollen of plant species other than citrus as an extra food resource.
Biology of P. kellyanus was first studied by Varikou, Tsitsipis, Alexandrakis,
and Hoddle, (2009a) and it was found that its lower development threshold is
10.2 o C and its thermal constant 204.6 day degrees [whereas 504 day degrees for
H. haemorrhoidalis (Rivnay, 1935)]. Therefore the Kelly’s citrus thrips is present
throughout the year in Crete (Chania) with its population increasing during citrus
flowering in spring as pollen is essential for its reproduction and development in
the citrus orchards (Varikou, 2006; Varikou, Tsitsipis, & Alexandrakis, 2009b).
Lemon is the best host among citrus for the survival and maintenance of the
thrips population due to the numerous flowerings during the year. Pezothrips
kellyanus is mostly attracted by blue colour traps (compared to yellow and white)
at the fruiting period but not during flowering or the rest of the year (Varikou,
2006).
Entomophagous arthropods of the Kelly’s citrus thrips have not been studied in
Greece. A predatory mite, Iphiseius (Amblyseius) degenerans (Berlese)
(Phytoseiidae), has been found in citrus orchards with high thrips populations in
Italy but its efficacy to control the thrips has not been not proved (Conti et al.,
2001). Hence, chemical control is applied at present.
Registered insecticides (active substances) for the control of thrips in citrus in
Greece include chlorpyrifos, fatty acid potassium salt and oxamyl (Authorized
Plant Protection Products Data Base of the Hellenic Ministry of Rural
Development and Food, 2008).
2.8. Mite Pests
Citrus are infested by a large number of mite species in Greece i.e. the tetranychids
Panonychus citri (Koch) and Tetranychus urticae Koch (Tetranychidae) and the
eriophyiids Aculops pelekassi (Keifer) and Aceria sheldoni (Ewing) (Eriophyidae),
which can cause serious damage on fruit production when outbreaks of the
population occur (Papaioannou-Souliotis, 1985, 1991, 1996; Papaioannou-Souliotis,
Tsagarakou, & Dermatas, 1992). However, the damages by mites are usually