The mosquito Aedes vexans and black fly Simulium maculatum are important blood-sucking pests in northern China. Control of these pests using current methods is difficult because of complex larval developmental sites. In the present study, lambda-cyhalothrin was applied as a barrier spray to vegetation and various structures surrounding human dwellings for control against the adults of each species. The barrier spray resulted in an 88.2–99.4% reduction in Ae. vexans abundance and a 67.8–89.6% reduction in S. maculatum abundance for 2 wk postapplication. Our results indicated that lambda-cyhalothrin applied as a barrier spray to vegetation and other structures that serve as harborage for adults of both species could be adopted as part of an integrated pest management approach against these pests.