Refining Gastrophysa atrocyanea (Coleoptera: Chrysomelidae) identification using UV marking in whole-plant assessment

The host plant quality is crucial for assessing the environmental safety of weed biological control agents, as they rely on the phenotypic characteristics of test plants in host specificity tests and for mass-rearing before field release. In this study, we explored the feasibility of using potted plants by applying ultraviolet (UV) fluorescent pigment to the elytra of the leaf beetle Gastrophysa atrocyanea. They were released separately on Rumex acetosa as the target weed and Buxus sinica var. insularis as a non-target plant in insect cages. UV marking reduced detection time by 2.7 times and increased the detection rates of female leaf beetles on the target weed compared to visible light, resulting in only 7.41% missing leaf beetles. Similarly, UV application reduced detection time by 2.3 times on the non-target plant, with no missing leaf beetles. Further, marking different sexes with UV pigments facilitated identification 4.8 times faster than visual light. The UV mark and recapture method exhibits promising potential in whole-plant testing, simplifying the identification of a potential biological control agent, G. atrocyanea, in insect cages under no-choice tests. Thus, UV marking enables the possibility of mass-rearing weed biological control agents and monitors the foraging behavior of phytophagous insects cost-effectively and non-disruptively in laboratory settings.