A wood preservative composition comprising a mixture of a fungicide which is a combination of a boric acid ester, which is soluble in an organic solvent and has a sterically hindered di-alcohol or tri-alcohol group, such as trihexylene glycol biborate, an organo-iodine compound, a triazole, and a synthetic pyrethroid insecticide, said fungicide and the insecticide being present in a sufficient amount that wood treated with the wood treatment material contains fungicide and insecticide in an amount of about 1 ppm to 5000 ppm, based on the weight of the wood after treatment.