Use of nets in olive orchard management

The use of nets to prevent insect damages on fruits is widespread, but there are no experiments for the control of the olive fruit fly, Bactrocera oleae (Rossi). The use of two plastic nets (HDPE 0.22 μ) with different meshes (0.8×0.3 mm and 1.0×1.6 mm) was investigated in an adult ‘Piantone di Mogliano’ olive orchard in the Marche Region (central eastern Italy). This local cultivar has been recently used for table olive production. The nets were installed on 4 trees per treatment, in early July. Chemically treated and untreated trees were used as controls. During July-August, the mean number of B. oleae adults captured with sex pheromone in yellow sticky traps was 3.96 per trap. In September, the percentage of total infestation on the dropped fruits was zero for the two net treatments, and 9.9 and 20.2% for chemically treated and untreated trees, respectively. Microclimate of the canopy was partially modified by the nets, in particular, under the net with 0.8×0.3 mm mesh, the air temperature decreased by 1-1.5°C and the relative humidity increased 2.5-4.5% when compared to outside from July to September. The use of nets increased the photosynthetic rate, the transpiration and the stomatal conductance in comparison with uncovered trees mainly in the South-West exposed portion of the canopy. The highest values of the above parameters were recorded for the net with 0.8×0.3 mm mesh. No significant differences were recorded for leaf chlorophyll content and fluorescence. The nets did not affect the course of fruit maturation trend and fruit production per tree. Present results are encouraging for high-value and organic olive productions, although further studies are required to optimize the management of nets in the orchard and evaluate their economical sustainability.