<i>Cosmolaelaps leeae</i> (Acari: Laelapidae) shows a high biological control effect on the pupae of <i>Megalurothrips usitatus</i> (Thysanoptera: Thripidae)

Megalurothrips usitatus (Bagnall) (Thysanoptera: Thripidae) is an important pest of leguminous crops in Asia, severely affecting cowpea quality and causing significant economic losses. The growing resistance of thrips to pesticides has reduced the efficacy of chemical control, thereby highlighting biological control as an increasingly important management strategy. Among natural enemies, predatory mites play a crucial role in suppressing M. usitatus populations. In this study, we evaluated the predatory functional response of Cosmolaelaps leeae Tseng (Laelapidae), a newly discovered indigenous predatory mite from Hainan cowpea fields, against M. usitatus. Results demonstrated that adult female C. leeae exhibited significantly higher predation rates than deutonymphs, consuming an average of 6.53 and 3.53 thrips pupae per day, respectively. Additionally, C. leeae displayed a prolonged oviposition duration (32.74 d) and high cumulative fecundity (84.05 eggs/female) when feeding on the pupae of M. usitatus. Furthermore, a cage experiment was conducted to assess the control efficiency of C. leeae on thrips populations under field conditions. Thrips population suppression increased significantly with escalating C. leeae release rates, demonstrating a density-dependent response, a characteristic of effective biological control agents. In comparative efficiency trials, C. leeae exhibited superior population suppression (1.21-fold, 1.46-fold, 1.71-fold) relative to the established commercial agent Stratiolaelaps scimitus at 3 identical release rates (5, 10, and 20 mites per pot). Overall, the predator mite C. leeae demonstrated significant suppressive effects on M. usitatus populations, suggesting its potential as a promising biological control agent.