Organic management of olive orchards increases the predation rate of overwintering pupae of Bactrocera oleae (Diptera: Tephritidae)

The olive fruit fly is the key pest of the olive tree and to date alternative and effective solutions to pesticide applications, such as conservation biological control techniques are scarce. Olive fruit fly overwintering pupae spend the season below the top soil, where they can be exposed to ground dwelling predators. In this study, we estimated the effect of predators on overwintering pupae sentinels considering both local and landscape variables in 18 olive orchards. We selected the experimental olive orchards in a Mediterranean-type environment, which had, as adjacent land use type olive, wood or Mediterranean garigue. In addition, we considered as local variables the distance of each pupae experimental unit from the edge with the semi-natural habitat, and the management of the fields while landscape scale variable considered the composition in semi-natural habitat type of the surrounding environment in buffer of 250 and 500 m radius. In organic orchards, exposed pupae were numerically more consumed than pupae in conventional orchards. No landscape effect was detected but we found a different effect of adjacent land use type, with enhanced predation rate of olive fly pupae in olive orchards adjacent to Mediterranean garigue patches. Further experiments could clarify the role of semi-natural habitats in supporting ground pest control and suggest close-to-nature solutions to pesticide strategy.