Japanese beetles, Popillia japonica Newman, are a quarantine issue for nursery shipments to certain U.S. states. The Domestic Japanese Beetle Harmonization Plan (DJHP) allows balled and burlapped (B&B) root ball immersion in chlorpyrifos or bifenthrin for P. japonica certification. Study objectives were: (a) to evaluate multiple insecticides as potential regulatory dips against third-instar P. japonica in 30-cm B&B, and (b) to determine the lowest effective rates. Tests were performed fall and spring from 2003 to 2007. All insecticide treatments reduced larval numbers compared with the untreated check treatment, with the exception of chlorantraniliprole and the lowest rate of trichlorfon in a fall test. Bifenthrin, carbaryl, chlorpyrifos, clothianidin, and trichlorfon and bifenthrin imidacloprid were the most effective insecticides. Larval numbers in acephate, deltamethrin, lambda-cyhalothrin, imidacloprid, and cyfluthrin imidacloprid treatments exceeded DJHP requirements at rates evaluated. Carbaryl, chlorantraniliprole, dinotefuran, thiamethoxam, trichlorfon, and cyfluthrin imidacloprid dips were more effective in spring than fall tests. The only insecticide that caused significant plant mortality was trichlorfon (rates ≥119.8 g active ingredient/100 L). Several insecticides not currently approved for use in the DJHP and reduced rates of DJHP-approved active ingredients, bifenthrin and chlorpyrifos, demonstrated suitability for regulatory programs against P. japonica.