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

Authors: LIU, TZU-CHIN - University Of California, Riverside; Burks, Charles; WILSON, HOUSTON - University Of California, Riverside

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2025
Publication Date: 2/4/2025
Citation: Liu, T., Burks, C.S., Wilson, H.S. 2025. Evaluation of a fluorophore for marking navel orangeworm (Lepidoptera: Pyralidae). Journal of Insect Science. 21(1). Article 12. https://doi.org/10.1093/jisesa/ieaf015.
DOI: https://doi.org/10.1093/jisesa/ieaf015

Interpretive Summary: The navel orangeworm is an important pest of almonds, pistachios and walnuts, and movement between orchards and crops is an important part of the pest potential of this moth. A commercially available fluorescent marker, applied as an aerosol mist in water, has the potential to enable mark-release-recapture experiments for improved understanding and prediction of movement between orchards. Moths treated with water aerosol alone or with one of the four available fluor colors all demonstrated an excellent ability to fly out of test cylinders and lived up to two weeks in field exposure tests. Instrumental examination of moths with a plate reader revealed that the green and yellow fluors were detected more readily than the red and blue fluors, and 70% of moths retained these colors after two weeks of field exposure. Direct evaluation with a hand-held blacklight provided better detection than the instrument, and by this method 90% of moths retained yellow and green colors after two weeks. Determination of suitable fluor colors and methods for this exterior marker will permit field mark-release-recapture studies that can improve methods for monitoring, predicting, and treating this and similar orchard moth pests.

Technical Abstract: Navel orangeworm, Amyelois transitella (Walker) (Lepidoptera: Pyralidae), 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 four colors (red, blue, green, and yellow) of a novel fluorophore marker (SmartWater®) for A. transitella adults. 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 four 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%) still 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 post-marking. 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 two fluorophore detection methods.