Sensitivity of current Tropilaelaps mercedesae monitoring methods in Apis mellifera colonies

The parasitic mite Tropilaelaps mercedesae (Anderson & Morgan) has recently been confirmed in western honey bee (Apis mellifera L.) colonies in western Asia and eastern Europe, marking a range expansion that necessitates effective monitoring methods to rapidly detect introductions into new regions, as well as promote integrated pest management where it is established. This study compared the sensitivity of current T. mercedesae monitoring methods, using the nearly globally distributed A. mellifera parasitic mite Varroa destructor (Anderson & Trueman) for comparison. Methods tested were bottom board sticky trap, worker brood cell uncapping, brood frame bump test, alcohol wash, and powdered sugar shake. Additionally, detection thresholds (cf. ED₅₀) were determined using dose-response analyses for the brood frame bump test, alcohol wash, and powdered sugar shake methods to understand how T. mercedesae worker brood cell infestation density influences the ability of different methods to detect T. mercedesae. Unlike for V. destructor, adult bee-based methods (alcohol wash and powdered sugar shake) had low sensitivity to detect T. mercedesae. The most sensitive method was bottom board sticky traps, followed by worker brood cell uncapping and brood frame bump tests. The adult bee-based methods (alcohol wash and powdered sugar shake) were the least sensitive methods of detecting T. mercedesae. Similarly, the alcohol wash and powdered sugar shake methods had a higher detection threshold than brood frame bump tests. This work provides valuable insights into T. mercedesae monitoring, especially as surveillance efforts increase in T. mercedesae-free regions considering the mite's recently detected range expansion.