خسارت Tetranychus urticae Koch (Acari: Tetranychidae) و Frankliniella occidentalis (Pergand) (Thysanoptera: Thripidae) روی گیاه رز: اثر تراکم های اولیه مختلف

The western flower thrips, Frankliniella occidentalis (Pergand) (Thysanoptera: Thripidae), and the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), are major economic pests of many ornamental plants including roses. Given the importance of aesthetic in roses; the effect of initial population density of T. urticae, F. occidentalis, and T. urticae/F. occidentalis (co-infestation) on chlorophyll content and flower shelf life was investigated on Rosa hybrid cultivar Vandenta under controlled conditions. Also, F. occidentalis damage to the flower petals in the presence and absence of T. urticae was evaluated. The evaluations were made 5, 10, or 15 days after infestations. The chlorophyll content was influenced by the initial population density and the infestation duration of T. urticae and T. urticae/F. occidentalis. However, the initial population density and the infestation duration of F. occidentalis did not significantly affect the leaf chlorophyll content. Although flower shelf life was not influenced by the T. urticae presence or density, the initial population densities of 10, 15, 20, 25, 30, and 35 F. occidentalis reduced flower shelf life by 6.4, 17.5, 23.9, 32.6, 36.7, and 43.5%, respectively in flowers harvested 5-days after infestation. The initial density of F. occidentalis influenced the necrotic surface area and the number of damaged petals in the absence or presence of T. urticae. The damage threshold in cut roses is considerably lower for F. occidentalis compared to T. urticae and preventive methods are recommended to minimize losses to this pest.