Lepidium draba L. (Brassicaceae), a perennial herb indigenous to Eurasia, was introduced to North America in the late 1800s. Recent surveys have shown that insect communities on L. draba in its exotic range have lower species diversity and richness but significantly higher insect abundance than those in the plant’s native range. North American herbivore populations were dominated by a few polyphagous species. Keane and Crawley (2002) hypothesized that polyphagous insect herbivores have less of an impact on abundance and dispersal of the exotic plant species than the surrounding native floral community. Therefore, it is predicted that even the high polyphagous insect densities observed in the field will have minimal impact on the growth and vigor of L. draba. We tested this hypothesis under controlled greenhouse conditions with four insects species commonly collected from North American L. draba populations: Lygus elisus Van Duzee, Plutella xylostella (L), Phyllotreta cruciferae (Goeze), and Ceutorhynchus americanus Buchanan. The impact of each insect herbivore species on potted L. draba plants was tested at several densities, both alone and in several herbivore species combinations. We found plant vigor and above-ground biomass were only impaired at the highest insect density treatments, and L. draba plants were able to compensate for the decreased above-ground biomass with increased vegetative reproduction. Combining two different insect species had similar results and showed only additive impacts and no synergistic interactions. These data support Keane and Crawley’s hypothesis, that the invasiveness of exotic plants is facilitated by their tolerance to generalist herbivory.