Using Cumulative Degree-Days Model for Prediction of Olive Fruit Fly, Bactrocera oleae Generations as an Important Element in the IPM Program in Tartus, Syria

Seasonal population density of the olive fruit fly, Bactrocera oleae (Diptera: Tephritidae) and its relationship to cumulative degree-gays using McPhail traps containing ammonium phosphate 3% as attractant during the two successive years 2021 and 2022, was studied in an olive field in Tartous Governorate, Syria. The traps were placed from the beginning of May and data were collected on a weekly basis until the olive fruit fly disappeared. Weekly samples of olive fruits were examined for signs of laying eggs until fruit harvest. The results showed that the fly activity started from late May until early December in 2021 and from early July to late November in 2022. The highest density for B. oleae was in July as it averaged 165 and 114.67 insects/trap in 2021 and 2022, respectively. According to the cumulative degree-days, it was found that B. oleae has 4 generations in the two seasons with a fifth partial generation in 2021 and with a thermal constant that reached in the first season 848.75, 956.25, 917.5, 879, 589.75 DD for each generation, respectively, and in the second season 869.5, 909.5, 878, 804 DD for each generation, respectively, without significant differences between the two seasons (x² = 7.21, P = 0.06 and x² = 6.86, P = 0.07), respectively. However, according to the model followed, a simplified table was proposed to calculate the cumulative degree-days instead of using mathematical models, based on the daily maximum and minimum temperatures. Keywords: Bactrocera oleae, degree-days, generations, prediction, Tartous, Syria.