Natural environmental control of Bactrocera oleae (Rossi): climate or parasitoids? A comparison between the Western Cape of South Africa and Sicily.Bactrocera oleae (Rossi), the olive fruit fly is considered not a continuosly serious pest of olive trees in the Western Cape of South Africa, in spite of the climate similar to Mediterranean areas. South African braconid parasitoids of B. oleae are more numerous than in Mediterranean areas, and until now their action has been considered the factor lowering the level of infestation due to the olive fruit fly, but no deep studies on its infestation levels and climatic factors influencing them were carried out in the past. Analyzing recent data on infestation levels collected in the Western Cape and Sicily, they appear similar in a regular mid- summer, differing at the end of summer-beginning of autumn, when in Sicily the climate becomes more humid than in the Western Cape. A comparison of climatic data regarding four years underlines that Somerset West and Franshhoek, in comparison with Trapani, have significantly lower minimum daily temperatures, a higher daily thermal excursion and a lower relative humidity in the last three months preceding harvesting.Parasitization rates on B. oleae of Western Cape and Sicily, recorded on both cultivated and wild olives (Olea europaea subsp. cuspidata in South Africa, Olea europaea subsp. europaea var. sylvestris in Sicily) are not substantially different, confirming that in South Africa three braconids, Utetes africanus (Szépligeti), Psyttalia lounsburyi (Silvestri) and Bracon celer (Szépligeti), are the main parasitoids, with the first one as leader in wild olives and the last one as leader in cultivated ones, while in Sicily the braconid Psyttalia concolor (Szépligeti) is the main parasitoid in both wild and cultivated olives. Nevertheless parasitism on B. oleae doesn’t reach effective levels of control in bats ragions.The climate, instead of parasitization due to braconids, is the main environmental factor limiting the olive fruit fly infestations in the Western Cape of South Africa.The introduction of parasitoids specific to the olive fruit fly is necessary in new invaded areas where they lack, but the attempt of providing them a more available amount of host fruits along the year, planting olive trees bearing fruits up to spring, could bring serious problems as those typical of Mediterranean areas where the European wild olive naturally grows.
|Number of pages||7|
|Journal||ATTI DELL'ACCADEMIA NAZIONALE ITALIANA DI ENTOMOLOGIA. RENDICONTI|
|Publication status||Published - 2017|