Which action decreases the effectiveness of exterior perimeter services?

Washing down hard surfaces decreases the effectiveness of exterior perimeter services because this action can wash away pesticide applications that are used to create a protective barrier against wood-destroying pests. When insecticides are applied to surfaces such as driveways, patios, and foundations, they need time to adhere and establish an effective barrier. If these surfaces are washed down shortly after the application, especially before the insecticide has dried or set, it can lead to a significant reduction in the amount of product that remains in place to intercept pests as they approach the structure.

In contrast, applying insecticides, sealing gaps and cracks, and removing debris and vegetation are actions that enhance the effectiveness of perimeter services. Applying insecticides establishes a chemical barrier; sealing gaps and cracks prevents entry points for pests, and removing debris and vegetation eliminates harborage areas and food sources that could attract pests to the structure.