Japanese beetles (Popillia japonica Newman) tend to feed gregariously and display a preference for feeding on already damaged foliage. Changing global atmospheric conditions, however, may affect the feeding preferences of this invasive species in the future. A series of preference tests with Y-tube olfactometers revealed that, while beetles preferentially responded to damaged leaves grown under ambient carbon dioxide over undamaged leaves grown under ambient carbon dioxide, they exhibited no such preference for damaged leaves grown under elevated carbon dioxide over undamaged leaves grown under elevated carbon dioxide. Damaged leaves produce elevated levels of green leaf volatiles (2-hexenal and 3-hexenal) (GLVs), as do leaves grown under elevated carbon dioxide irrespective of damage status. These compounds are used as kairomones by many herbivorous insects for host plant location and may serve a similar function for Japanese beetles. If such is the case, greater abundance of P. japonica on soybean foliage grown under elevated carbon dioxide regardless of previous damage may be more common under future atmospheric conditions.