Question
Stephenville Texas is in Central Texas  I have lost
10-12 Post Oak Trees.Now two more are dying.

The trees seem to die within two to three weeks.Leaves turn
brown in a few days.when I remove the trees the roots seem
soft and spongy and moist .A chain saw will have difficulty
because of the root condition.The disease seems to spread
to the adjoining trees and doesnt skip around.Any suggestons?

Answer
May be Oak Wilt disease. Oaks in parts of Texas have been killed lately. I would contact the local office of the Texas Forest Service (State Agency) and ask one of their Forester to take a look and advise you.
Here is a web link to Oak wilt in Texas and where to get help.  http://www.texasoakwilt.org/