The effects of rubidium chloride were characterized on immature and adult Grapholita molesta (Busck) in an effort to determine its suitability as a label to mark, release and recapture this species in field-based dispersal studies. Neonate G. molesta (Busck) larvae were fed lima bean-based diet enriched with 0, 600, 3,000 or 6,000 mg RbCI/L liquid diet (ppm). Both male and female adult G. molesta were successfully marked at the 3 highest concentrations. Increasing concentrations did not alter pupal mass or larva-to-adult development (first instar to adult death), but adult longevity decreased in response to increasing Rb concentrations in diet. All males and 83.3% of females reared on diet with 6,000 ppm RbCI retained a detectable Rb signature through 168 h post eclosion. Labeled males were more likely to exhibit stationary zig-zag flight prior to flying upwind to a sex pheromone lure in a wind tunnel. These experiments demonstrate that rubidium chloride may be used to label immature G. molesta for subsequent release and recapture without significant detrimental effects to the insects.