a wood treating composition is provided , comprising an aqueous solution containing a specified amount of zinc ion ; a specified amount of ammonium thiocyanate ; and a specified amount of zinc oxide solubilizing amount of ammonia , the composition having a ph of 9 or more . the composition may be provided by means of an aqueous ammoniacal solution of zn 2 . the composition may also include one or more of the following : cupric ammonium ions , a vinyl polymer latex , optionally , an acidic organic surfactant compound which is soluble in the ammoniacal salt solution , or an additional fungicidal agent .