Efficacy of low-copper-content and silicate-based particle film products against olive fruit fly (Bactrocera oleae Rossi) infestations in olive groves

The olive fruit fly (Bactrocera oleae) is the most important olive pest worldwide, which can cause total yield losses in olive groves where its population is not controlled. The current knowledge suggests that some commonly used copper-based fungicides and silicate-based particle films can contribute to reductions in B. oleae infestations. The aim of this study was to determine the efficacy of commonly used copper fungicides, two different low-copper products (alternative fungicides), and a silicate-based particle film for B. oleae infestations. This study lasted from July to October 2023 in an olive grove on the Croatian coast. It was set up on the most widespread Croatian cultivar, Oblica, and the following treatments were applied: the commonly used copper oxychloride (37.5 % Cu), copper gluconate (12 % Cu), a low-copper product (1 % Cu), a silicate-based particle film product, a mixture of a low-copper (1 % Cu) and a silicate-based particle film product, and water (the control). The fruits were sampled every 15 days and examined for the presence of B. oleae. Total (% of fruit showing signs of infestation) and harmful infestations (% of larvae, pupae, or exit holes) were determined. All of the treatments, with the exception of copper oxychloride, significantly reduced the total infestation of B. oleae compared to that with the control. While all of the treatments were found to be more effective in reducing harmful infestations than the control, only the silicate-based particle film product and the combination of the low-copper product and the silicate-based particle film product significantly reduced infestations. These results indicate that the silicate-based particle film product and the mixture of the low-copper product and the silicate-based particle film product were the most effective in reducing B. oleae infestations. These products might have an important role in future olive fruit fly management programs.