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Four species of entomogenous nematodes [Steinernema feltiae (Filipjev) [=Neoaplectana carpocapsae Weiser] ('All' strain), S. glaseri (Steiner), Heterorhabditis heliothidis (Khan, Brooks & Hirschmann), and Heterorhabditis sp. ('Holland' strain)] were compared with two insecticides (chlorpyrifos and isofenphos) for control of third- (last-) instar larval Japanese beetles (Popillia japonica Newman) and European chafers [Rhizotrogus majalis (Razoumowsky)] in potted Japanese yew (Taxus cuspidate Siebold & Zuccarini). Efficacy was evaluated 17-21 d after treatment. Heterorhabditis sp. ('Holland' strain) at 92 nematodes per cm2 of soil surface and H. heliothidis at 192 nematodes per cm2 provided >90% control of Japanese beetles compared with 71% for chlorpyrifos (9.0 kg [AI]/ha) and 84% for isofenphos (4.5 kg [AI]/ha). S. glaseri provided 84 and S. feltiae 29% control (both at 385 nematodes per cm2 ). Both nematodes and insecticides were less effective in controlling European chafer larvae. Control with nematodes ranged from 46 to 59% with S. glaseri, H. Heliothidis, and Heterorhabditis sp. at 385 nematodes per cm2 , whereas S. feltiae at 385 nematodes per cm2 did not significantly reduce larval survival compared with the untreated control. Chemical control of European chafer larvae resulted in reductions of 44 and 62% with isofenphos and chlorpyrifos, respectively.