Pressure-treated wood used for fence posts and footings will be treated to a higher level of resistance (called “ground contact”) than wood used above ground.  For the above ground portion of your fence, debris such as leaves, mulch, and trash can block moisture from evaporating and create long term wet areas that will be vulnerable to rot, decay and termites.  Keep your fence clear of leaves and debris and make sure that mulch is not piled up along the bottom boards. As long as the wood is exposed to freely moving air, the pressure treatment will be effective.