Abstract: Most structural timber species now used in the North China's rural areas are poplar, willow, elm etc, which are fast growing trees but whose woods are very susceptible to biological deterioration. It is, therefore, very important to conduct some simple and effective treatments in those region including both laboratory tests and field studies. Some water-borne and oil-borne preservatives have been were selected for these purposes. Field tests were performed at Daxing County, southern suburb of Beijing.Eighteen different preservatives were prepared and their effectiveness to the preservation of Populus tomentosa Carr were based on their toxicities against wood decaying fungi and termites. As well, through two years observations in the rural areas, no cases of decay and insect-bite were found on these structural wood members which had been previously treated with those selected preservatives. On the other hand, several insect-bite evidences cases were found on some individual untreated purlins.

Key words: Poplar, Preservative, Nature decay resistance, Nature resistance to termite, Toxicity of preservatives, Coriolus versicolor (L.ex Fr) Quel, Reticulitermes chinensis Snyder