Using Environmental DNA to Detect and Identify Sweetpotato Whitefly Bemisia argentifolii and Twospotted Spider Mite Tetranychus urticae in Greenhouse-Grown Tomato Plants

Environmental DNA (eDNA) consists of genetic material shed by living organisms, including those that are deceased, offering a unique opportunity to detect and identify terrestrial insect pests without requiring visual identification. The sweetpotato whitefly, Bemisia argentifolii, and the twospotted spider mite, Tetranychus urticae, are notorious for causing crop losses through virus transmission and direct feeding. Our study aimed to: (1) assess the effectiveness of B. argentifolii literature-based PCR primers compared to newly developed primers for eDNA amplification, (2) evaluate the sensitivity of conventional PCR (cPCR) and real-time quantitative PCR (qPCR) for detecting eDNA of B. argentifolii and T. urticae, (3) establish a rapid eDNA processing methodology using the LGC Biosearch Technologies QuickExtract DNA extraction kit and the Qiagen DNeasy Blood and Tissue kit, and (4) test the specificity of the developed primers against non-target species. B. argentifolii and T. urticae were confined to tomato leaves (Solanum lycopersicum) using clip cages for 24 h, after which eDNA was collected from leaf surfaces using a water spray method, filtered, and processed for DNA amplification. While literature-based primers showed sufficient sensitivity, their specificity for eDNA applications was inadequate, prompting the design of novel PCR primers for both pest species. Positive eDNA detection was achieved with both amplification methods, with qPCR proving more reliable than cPCR due to the latter's inconsistent performance with positive control samples. We also introduced a rapid eDNA processing approach using the QuickExtract DNA extraction kit, contrasting it with the more conventional Qiagen DNeasy Blood and Tissue kit. We believe that our findings are the first step toward the practical use of eDNA as a highly sensitive, early detection technique.