Reduction of olive fruit fly damage by early harvesting and impact on oil quality parameters

Abstract

Olive fly population was monitored weekly on two olive cultivars (Buža and Istarska bjelica), from June until mid October, in Rovinj and Livade (Istria, Croatia). The number of eggs, larvae, and pupae was established and the total and active infestation was calculated. The fruit infestations for early and for late harvesting were obtained based on the calculated regression equation. For the prediction of the changes in the oil quality parameters linear regression slopes, obtained by Koprivnjak et al., were used. We established a strong positive correlation between DD accumulation and cumulative capture of flies, as well as with the total and active fruit infestations. According to obtained results it can be stated that I. bjelica is less sensitive to decrease in total phenols amount, to increase in free fatty acids mass ratio and to increase in peroxide values comparing to Buža. Moreover, the differences in investigated parameters between earlier and late harvesting dates in I. bjelica are lower due to lower infestation predicted for both harvesting dates and due to lower sensitivity to the changes in quality parameters. Therefore, early harvesting date as a model for preventing fruit damage and as a model for preventing negative change in oil quality parameters is a valid tool. However, the effectiveness of this model could also depend on the characteristics of olive cultivar.Practical applications: Understanding the factors that affect the olive fly attack is the basis of scientific and practical interest in the production of olives and olive oil. Research of monitoring methods allows reliable forecasting and determining protection measures. Knowledge about this topic could contribute to the reduction of insecticides use and to the improvement of quality and food safety concept in olive oil production.Damaged olive fruits are proved to directly affect the quantitative and qualitative properties of olive oils. The most important fruit damage is caused by the olive fly (Bactrocera oleae Gmelin).