Copper and kaolin sprays as tools for controlling the olive fruit fly

Abstract

The olive fruit fly, Bactrocera oleae (Rossi) (Diptera: Tephritidae), is the most damaging pest of olive crop in the main growing areas. The control of this pest is based on insecticides, but more sustainable strategies are needed to reduce negative impacts such as pesticide residues, development of insecticide resistance or effects on non-target organisms. In a three-year field study, the effectiveness of preventive kaolin and copper (Bordeaux mixture) applications were evaluated. Natural pest control in olive groves is very valuable and must be preserved, so the effects of these treatments on non-target arthropods were also investigated compared to conventional dimethoate bait sprays and paying special attention to natural enemies. Kaolin sprays reduced the damage of B. oleae to levels that allow high quality oil production, even with a very high pest incidence. Copper treatments provided a certain protection that was insufficient at high infestation levels. No significant changes in abundance and number of arthropod morphospecies were detected. However, the diversity of arthropods, measured by Shannon index, was reduced by dimethoate baits and kaolin sprays and fewer predators were found in dimethoate treated trees. A significant alteration of the natural enemies’ community was also detected by Principal Response Curve (PRC) analysis in plots sprayed with kaolin, in the second year, with the coccinellid beetle Scymnus marinus (Mulsant) particularly affected. Monitoring long-term effects of kaolin sprays on natural enemies is advisable, while environmentally-friendly measures are applied to favor their presence.