Phosphine Susceptibility Screening of Three Different Stored Product Beetle Species by Using Three Diagnostic Techniques

Phosphine resistance represents a major challenge for stored product protection worldwide. In this study, we evaluated populations of Oryzaephilus surinamensis, Rhyzopertha dominica, and Cryptolestes ferrugineus collected from different regions using three diagnostic protocols: (i) the FAO test (30 ppm for 20 h); (ii) a dose–response bioassay (50–1000 ppm for 3 d); (iii) the Phosphine Tolerance Test (3000 ppm for up to 270 min). Results indicated that while several O. surinamensis populations remained susceptible, all tested populations of R. dominica and C. ferrugineus were resistant. The three protocols produced comparable outcomes, supporting their reliability for diagnosing resistant populations. This is the first study to simultaneously compare three diagnostic approaches across multiple beetle species, providing the basis for a harmonized global diagnostic framework. These findings underscore the need for continued monitoring and highlight the importance of standardized tools for resistance management.