You may not have a choice. They can literally eat you out of house and home in no time at all. They are very, very rare but they must be exterminated immediately. Eliminate the cause and they should go away. Did we mention the are the biggest termites found locally.
Big termites have big appetites.
Generally, State laws require that sellers disclose any problems that a home may have. Termite and wood destroying organism problems are included. State laws do not generally require that you do anything about the problems, just that you disclose them. So, unless the home is free of the above, they will not fund the loan. Thus the need to correct the problems before escrow will close.