This is the answer I gave in the FMCA Forum:
Some say you can spread a dry powder (Ortho Fire Ant killer) or spray (Home Defense) all around the coach, but this will not help for those that spring out under the coach. I just look around every day and treat those areas that crop up as they do so. You should be able to reach areas under the coach with the spray.
Fortunately we are now on a concrete pad so just have to spray around the coach as they crop up.