The current study evaluated the effect of different classes of insecticides against bagworms (Lepidoptera: Psychidae) on arborvitae by using a laboratory bioassay that allowed us to simultaneously evaluate the feeding rate, growth, and mortality of larvae. Soil application of the systemic insecticides dinotefuran and (to a lesser extent) chlothianidin increased larval mortality and reduced the feeding rate and growth of larvae, up to 50 d posttreatment. The effectiveness of systemic insecticides against bagworms makes them well suited to control bagworms on tall trees heavily infested in the upper canopy. Chlorantranilipole and indoxacarb were as effective in controlling bagworms as other contact insecticides commercially available (spinosad and bifenthrin). Chlorantraniliprole had a residual effect 10 d posttreatment and may therefore provide an effective tool to protect the foliage of arborvitae against bagworms over a sustained period.