DOES HOST-RANGE INFLUENCE SUSCEPTIBILITY OF HERBIVOROUS INSECTS TO NONHOST PLANT PROTEINASE-INHIBITORS

We examined the influence of proteinase inhibitors on digestive enzyme s and development of oriental beetle, Exomala orientalis Waterhouse, E uropean chafer, Rhizotrogus majalis (Razoumowsky), Phyllophaga white g rub, Phyllophaga anxia (LeConte), cranberry root grub, Lichnanthe vulp ina (Hentz), Japanese beetle, Popillia japonica Newman, Asiatic garden beetle, Maladera castanea (Arrow) (Coleoptera: Scarabaeidae), and the black cutworm, Agrotis ipsilon (Rottemburg) (Lepidoptera: Noctuidae). We demonstrated that all species within our test group had alkaline m idguts that contained proteinase activity that could be inhibited, in vitro with serine proteinase inhibitors. Our data suggests that host r ange may influence the susceptibility to non-host inhibitors. Chronic ingestion of the serine proteinase inhibitor, Kunitz-soybean trypsin i nhibitor (STI), significantly reduced proteolytic activity in vivo in those species with relatively specialized feeding habits (i.e., cranbe rry root grub, Japanese beetle, Asiatic garden beetle, and black cutwo rm). Chronic ingestion of STI also resulted in reduced larval growth a nd delayed pupation for black cutworm, and elevated larval mortality f or Japanese beetle. However, chronic ingestion of STI did not influenc e larval survival for those species with relatively generalized feedin g habits (i.e., oriental beetle, European chafer). Based on these resu lts, we propose mechanistically-based criteria for selecting proteinas e inhibitors for phytochemical defense against herbivorous insects.