Abstract: Three aqueous solutions of quaternary ammonium salt were mixed with copper salt to prepare wood preservatives (FFJ-1, FFJ-2 and FFJ-3).Treatments of lumber with these preservatives were carried out by conventional vacuum pressure impregnation.Soil block evaluations of the preservatives against brown rot fungi[ Poria placenta (Fr.)Cooke]and white rot fungi[ Coriolus versicolor (L.ex Fr.)Quel]indicate good decay resistance by FFJ-1,FFJ-2 and FFJ-3 against white rot at low retention, 0.1% copper(weight/weight).However,higher retention is needed for brown rot protection,1% copper(weight/weight).Also soil block decay tests were performed with chlorothalonil(CTL)pentachlorophenol sodium(PCP Na)and tradimefon against white rot fungi.The effects of FFJ-1,FFJ-2 and FFJ-3 against white rot fungi are equivalent to those of CTL,but superior to those of PCP Na and tradimefon.

Key words: quaternary ammonium salt, wood preservative