Blocks (10 x 10 x 5 mm³) of Pinus patula and Eucalyptus grandis were impregnated to 0, 1.5, 3.0 and 4.5 kg/m³ 2-sec-butyl, 4, 6 dinitrophenol (DNBP). They were monitored microscopically and for weight losses over 16 weeks against monocultures of Coriolus versicolor and Coniophora puteana. Treated ministakes (10 x 10 x 100 mm³) and blocks in soil contact were similarly monitored to determine weight losses and microbial succession. Weight losses increased progressively. Final losses after soil burial were 10% in Eucalypt and 4% in Pine treated to 4.5 kg/m³ DNBP. Comparable figures after Coriolus exposure were 30% in Eucalypt and 7% in Pine. Both timbers were protected against Coniophora by 3.0 kg/m³ DNPB when weight losses never exceeded 3%. Pine was less colonised than Eucalypt and least isolates were obtained from samples containing most DNBP. Succession was always initiated by bacteria and molds after 2 weeks. Basidiomycetes colonised Eucalypt after 6 weeks but were not observed in Pine. Bacteria attached to wood by glycocalyces were observed to produce lysis troughs in S3 layers of cell walls of DNBP-treated samples of both woods.

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