engleski

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

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 second generation of olive fruit fly (Bactrocera oleae (Gmelin)) which appears in September and October. The aim of investigation was to establish how the increase of fly population influences the fruit infestation over the time. The next question is how it could reflect on qualitative properties of olive oils. The infestation of fruits is expected to be lower at earlier harvesting which will reduce the negative impact of damage on the oil quality parameters. Olive fruit fly population was monitored weekly, from June until mid October, in Rovinj and Livade. Yellow sticky traps, baited with pheromone, and McPhail traps, baited by 3% hydrolyzed protein, were used. After the first ones got caught, fruit samples were collected once a week. The number of eggs, larvae and pupae was established and the total and active infestation (L2, L3 and pupae) was calculated. The mean degree-day (DD) accumulation (above 10°C) was calculated according to the collected climatic data. The fruit infestations for early (16 October) and for late harvesting (5 November) 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. (2010), were used. We established a strong positive correlation between DD accumulation and cumulative capture of flies on both types of traps, as well as with the total and active fruit infestations. The predicted fruit infestation would result with the decrease of the total phenols concentration, between 0.86 and 4.65%, and with the increase of the free fatty acids mass ratio, between 3.6 and 7.78%, comparing with the oils from healthy fruits. Growing region and climatic factors have an impact on the olive fly population and harvest dates, which can reflect on the fruit infestation and oil quality.

Olive; Bactrocera oleae; infestation; harvest; olive oil quality

nije evidentirano