2nd Place: Evaluating the accuracy and sensitivity of a DNA-based assay for discriminating spotted-wing drosophila from common drosophilids in Indiana

Spotted-wing Drosophila (SWD), Drosophila suzukii, is an economically-important pest of small fruits worldwide. Currently, timing of management is based on morphological identification of adult flies captured in baited monitoring traps; however, distinguishing SWD from other native drosophilids in traps is time-consuming, requires magnification, and may still be prone to error by untrained users. Taken together, these factors can limit the adoption of monitoring tools by stakeholders. Alternatively, DNA-based diagnostic methods, like loop-mediated isothermal amplification (LAMP), can improve the accuracy of detection and reduce identification time by utilizing a colorimetric assay that changes from pink to yellow when target DNA is present. To date, no studies have evaluated a LAMP assay as a diagnostic tool to discriminate between SWD and congener drosophilid species, which commonly occur in traps and may present false positives.

We designed a set of SWD primers targeting the COⅠ gene and found the LAMP assay accurately detected SWD with as little as 0.1 ng/ul of DNA. The optimal conditions to consistently detect SWD DNA with high accuracy was incubation at 63 ℃ for 50 minutes. Furthermore, the LAMP assay successfully discriminated between the DNA of Drosophila suzukii and two congener species, D. affinis, and D. simulans, when tested in individual reactions, with or without formal DNA extraction. With results achieved in less than 1 hour and testing costs of $2-$4/sample, the LAMP assay holds potential as a reliable diagnostic test to improve detection and adoption of monitoring tools for SWD in small fruit systems.