Many years ago TN had a B737 that had a family of rodents in that that just didn't want to leave the plane, no matter what.
After all sorts of measures were tried the solution was found............Suffocate them.
The aircraft was parked "on the fence" with all of its external orifices sealed off and a number of CO2 cylinders were placed in the cargo holds.
One, two, three..........Open the cylinder valves, jump out of the cargo holds and slam the doors, come back a day later and hunt for the bodies !!!
Problem "Solvered" with no nasty chemicals !
ST