Particle Films Combined with Propolis Have Positive Effects in Reducing Bactrocera oleae Attacks on Olive Fruits

Abstract

The olive fruit fly, Bactrocera oleae, is a major pest of olive trees in several areas of the world. Testing novel preventive methods against B. oleae infestations is paramount. The use of particle film in eluding B. oleae and avoiding oviposition is one of the main strategies adopted by olive growers; however, choices are often limited to kaolin. Under field conditions, we tested the efficacy of novel compounds, including particle films, for their effectiveness as oviposition deterrents against B. oleae. The trial was conducted from July to October 2021 in an olive orchard located in central Italy. One olive variety, Borgiona, was selected and sprayed with propolis, rock powder, kaolin, the mixture of propolis and rock powder, the mixture of propolis and kaolin and water (control). Laboratory analyses were conducted to study the effects of the treatments on the fruit maturity index. As per the field trial, the rock powder and propolis mixture caused a reduction of B. oleae infestation with respect to the control (water), similarly to kaolin. Moreover, the mixture of kaolin and propolis exhibited the best results among all treatments. When mixed with propolis, particle films showed higher protection from B. oleae than when applied alone, suggesting a synergistic effect, and demonstrating an interesting role of propolis as an adjuvant. No delay in fruit maturity was noticed. Our results indicate that the tested products have the potential to be incorporated into management programs of B. oleae, although possible side effects on olive physiology require additional investigations.