A physical control method to prevent entrance and exit of adult mosquitoes from breeding areas within the storm drain line was tested. Open-ended fabric tubes were placed in lateral pipes which connected the catch basins to the storm drain line. One end of the tube was allowed to collapse and caused a barrier to adult movement but permitted water flow. After tube installation in the line, the number of adult mosquitoes trapped was reduced by 87-96%. Effectiveness of the barrier system was confirmed by an 80-89% reduction in adults trapped in yards of houses adjacent to the storm drain line.