Evaluation of a fluorophore for marking navel orangeworm (Lepidoptera: Pyralidae)

Navel orangeworm, Amyelois transitella (Walker), is a key pest in California's almonds, pistachios, and walnuts. This insect's strong dispersal capacity can potentially undermine the efficacy of localized management efforts. The timing and extent of A. transitella movement between orchards remain unclear, and more studies are needed to better characterize its landscape ecology. Mark-release-recapture studies offer a potential solution but require a reliable insect marker that is durable, easily identifiable and has minimal impacts on A. transitella longevity and flight ability. To address this, we evaluated 4 colors (red, blue, green, and yellow) of a fluorophore marker (SmartWater) for adult A. transitella. We conducted laboratory assays to assess moth flight ability and mortality, as well as marker persistence over time using both quantitative (plate reader) and qualitative (visual observation) fluorophore detection methods. Results demonstrated that none of the 4 colors negatively affected A. transitella flight ability or mortality. Green and yellow markers were persistent and readily identified by both detection methods, unlike blue and red markers. Although marker degradation was observed over time with the quantitative method, a high percentage of moths (70.3%) retained green and yellow markers after 14 days. In contrast, these markers did not show significant degradation using the qualitative method, with over 94.2% of moths showing fluorescence 14 days postmarking. These findings highlight the strong potential of green and yellow markers for field studies with A. transitella. We discuss their use in future mark-release-recapture studies and compare the 2 fluorophore detection methods.