Seasonal and Annual Occurrence of Mediterranean Fruit Flies (Diptera: Tephritidae) on Chios Island, Greece: Differences between Two Neighboring Citrus Orchards

Two orchards that contained mainly citrus and a few other hosts were monitored during 1991-1993 for Ceratitis capitata (Wiedemann) on the Mediterranean island of Chios, eastern central Greece. The orchards are located ≈0.5 km apart in a citrus producing plain and differ mainly in their numbers and relative abundance of apricots, sweet oranges, and bitter oranges. Overall, captures in Jackson traps baited with trimedlure were low in June and most of July and also in December and January, high from August through November, and absent from February through May. Early in the season, adult abundance was closely associated with the presence of ripe apricots, Primus anneniaca L., and bitter oranges, Citrus aurantium L., whereas later with the presence of sweet oranges ‘Valencia’, C. cinensis Osbeck, and also figs, Ficus carica L., which are scattered in the area. Despite the close proximity of the 2 orchards and the bridge of hosts between them, captures started each year ≈1 mo earlier (mid-June) and the total captures were higher in the one orchard that contained apricots and several bitter oranges than in the other orchard containing a few bitter oranges. The presence of ripe bitter oranges in the former orchard kept flies from infesting sweet oranges, which were also susceptible. These results suggest that host plant composition and availability and especially the presence of highly preferred hosts create a large amount of local variation in C. capitata abundance. Implications of our findings are discussed with respect to the efficiency of the currently used trapping systems for the early detection of C. capitata and the importance of sampling fruits from preferred hosts.