Naturally Abscised Fruitlets as a Potential Breeding Resource for Early Spring Buildup of Medfly Populations in Temperate Regions

The Mediterranean fruit fly (medfly), Ceratitis capitata, is considered one of the most destructive fruit pests worldwide. Female medflies prefer to lay eggs in ripening, ripe, or overripe fruits. In deciduous orchards of temperate regions, fruitlets (juvenile fruits) of early cultivars could represent the earliest spring resource with a potential host function for medflies. However, little is known about the medfly female’s ability to ovipositing and complete breeding in fruitlets. To clarify the possible role of fruitlets, the suitability of key-host fruitlets for the oviposition of medflies and the further development of immature stages were examined in laboratory conditions and an attempt was made to assess the degree of infection of fruitlets collected in the field. Additionally, the development of the overwintering medfly population and the putative use of fruitlets as a resource for early population growth were simulated using the PESTonFARM model optimized to reflect specific features of medfly biology and behavior. Our laboratory data demonstrate that nectarine and pear fruitlets can support the full development of medfly offspring. However, no medfly pupae were obtained from a sample of 14,000 fruitlets collected at the farm. The simulation showed that the sample number needed to detect with at least 95% certainty rare cases of medfly pupae or adults emerging from infected fruitlets is several tens of thousands, which is several times more than the actual number of fruitlets used in our study. Our research suggests that the fruitlets of some cultivated fruit species can potentially constitute a viable food resource for the development of the earliest generation of spring medflies, with implications for medfly Integrated Pest Management (IPM).