The estimation of optimal harvesting period for olives, based on losses in the physical and mechanical properties caused by olive fruit fly infestation at different orchard altitudes

Abstract

This study estimated the optimal harvesting period for Ayvalik olives in Turkey based on losses in the physical and mechanical properties caused by olive fruit fly (Bactrocera oleae (Rossi)) infestations. The study was conducted for three years at different orchards at altitudes of 84, 101, 126, 151, and 168 m ASL. Sixty fruits from each harvesting period were selected between September 1st and December 10th at 0, 20, 50, 80, and 100-day intervals after the first harvest. The physical and mechanical properties of olive fruits were determined, and the change rates between damaged and undamaged fruits of these properties were calculated. The optimal harvesting period was obtained using the response surface method (RSM). ANOVA results were analyzed regarding the interactions of the three factors affecting the losses in the physical and mechanical properties of the fruit. 2D contour plots of the factors were drawn and interpreted according to the order of the effects on the responses for which regression equations were obtained. The optimal harvesting period for olives was estimated to be the 62nd day (from September 1st), at 168 m altitude, with a desirability of 0.8463 and a minimum damage rate of 10.9%. Results indicated that the losses in the physical and mechanical properties were severely affected by the damage caused by fruit flies. These losses were also due to the orchard altitude and the harvest after the first period.