Molecular assessment of predation efficiency of Orius similis (Hemiptera: Anthocoridae) on Frankliniella occidentalis (Thysanoptera: Thripidae) and Tetranychus urticae (Acari: Tetranychida)

The generalist predator Orius similis plays a crucial role in controlling the pests Frankliniella occidentalis (Pergande) and Tetranychus urticae Koch. To assess the effectiveness of O. similis in controlling these pests in bean field, we conducted field surveys and used DNA molecular analysis to quantitatively measure the levels of predation on each prey. Field surveys conducted from June 18 to August 7, 2021, showed a linear increase in the population densities of O. similis, F. occidentalis, and T. urticae. The population density of F. occidentalis and T. urticae peaked on July 16, whereas that of O. similis peaked on July 23. The highest positive rate for F. occidentalis and T. urticae was observed on July 23 and 16, respectively. The positive detection rate to F. occidentalis was significantly higher than that of T. urticae (t = 7.659, df = 14, P < 0.0001). The DNA half-lives of F. occidentalis and T. urticae were estimated at 4.44 and 2.60 h, respectively, based on the positive detection rates of both preys during the digestion time in O. similis. These results suggest that molecular intestinal content analysis can be effectively used to quantitatively evaluate the control effect of O. similis on F. occidentalis and T. urticae.