Continuous Winter Reproduction and Growth of the Mediterranean Fruit Fly (Diptera: Tephritidae) in Heraklion, Crete, Southern Greece

Abstract

The objective of this work was to study the effect of winter low temperatures on survival, reproduction, and growth of immature stages, and the host fruit infestation ability of the Mediterranean fruit fly, Ceratitis Capitata (Wiedemann), wild population in the southernmost part of Greece. Adult flies were monitored using Jackson and McPhail traps from November to May over a period of 3 yr. In January-March, absolute minimum and maximum air temperatures were 1-4.5 and 19-26 degreesC, respectively, whereas the average monthly minima and maxima were 6.2-9.7 degreesC and 15.4-18.5 degreesC, respectively. Adults were found at every inspection period (every second week) in at least one of the trapping systems used or the years of the study. Until the beginning of April developed eggs and sperm were found in >70% of females trapped. From mid-April until mid-May, 20-70% of females were fecund and fertile. This increased at the end of May- beginning of June to high percentages, >80%. Females survived in cages in the field an average of 4 mo in winter-spring, with some females surviving 5-6 mo. Infested 'Navel', 'Valencia' oranges, or bitter oranges could be found throughout the experimental period in all 3 yr and live eggs were always detected in infested fruits. Grown larvae were found in relatively high percentages of infested fruits until March, especially in bitter oranges, which appear to be a preferred host (up to 25 pupae per infested fruit). In April-May, grown larvae were seldom detected. In winter, larval development from the time of fruit sampling until larval exit often took 1.5-2 mo. The duration of the pupal stage under field temperatures was approximate to 2 mo for those pupae formed between December and February. This was reduced progressively to 10-20 d for those pupae formed in May. The mortality of young larvae (still near the oviposition hole) was between 40 and 70% from November until May, whereas adult emergence from pupae kept in the field fluctuated between 20 and 80%. In conclusion, under the conditions of southern Greece (Heraklion, Crete) the Mediterranean fruit fly continues reproduction and growth during the cooler part of the year but at reduced rates and with longer duration of larval and pupal stages. This must be considered in control or eradication applications