A liquid insecticide solution comprising a 5% to 20% water solution of a disodium octaborate tetrahydrate (“DOT”) mixture comprising disodium octaborate tetrahydrate, colored pigment, and a bittering agent of either sucrose octa-acetate and denatonium benzoate, is provided. Preferably, the insecticide solution is prepared by stirring a powdered DOT mixture into water. Methods for treating wood surfaces and preparing bait stations with liquid insecticide solutions prepared with D.O.T. mixtures are also provided.