Odor Preference, Feeding, Survival, and Reproductive Fitness of the Invasive Larger Grain Borer Prostephanus truncatus on Acorns of Three Native North America Oak Species

The larger grain borer, Prostephanus truncatus (Horn), is an invasive pest on stored grains but can also exploit non-grain food sources. Currently, this species has a limited distribution in North America but possesses the potential to further expand across the continent. Alternative non-grain foods could play a role in range expansion and previous research has shown that acorns can be a suitable food for the lesser grain borer Rhyzopertha dominica (F.), a closely related grain pest. Here, we assessed the odor preference of P. truncatus for acorns from black oak ( Quercus velutina ), red oak ( Quercus rubra ), and bur oak ( Quercus macrocarpa ) compared to maize and wheat, and analyzed their volatile organic compound (VOC) profiles. Further, we measured P. truncatus feeding and reproduction on these acorns. Results demonstrated that P. truncatus responded to volatiles of each acorn species but responded most positively to bur oak acorns. Interestingly, bur oak acorns were also more attractive than maize, its main host grain. VOC profiles showed that two compounds emitted from bur oak acorns, 3-hepten-2-one and 2-(5-methyl-furan-2-yl)-propionaldehyde, were unique compared to other treatments, which may be important for odor preference. P. truncatus also preferred to feed on bur oak acorns over other oak species. Bur oak was the only acorn species tested in which F ₁ progeny were detected. These results suggest that P. truncatus exhibits evolutionary plasticity that enables it to survive on acorns in the absence of grains, highlighting an elevated risk of landscape-level invasion by this pest in North America.