The wood preservative potentials of heartwood extracts of Milicia excelsa and Erythrophleum suaveolens

The ability of heartwood extracts of two very durable tropical hardwood species (Milicia excelsa (Welw.) C.C. Berg. Syn Chlorophora excelsa (Welw.) and Erythrophelum suaveolens (Guill. & Perr.) Brenan Syn Erythrophleum guinensis) to suppress attack by Lenzites trabea (a brown rotter) or by Polyporous versicolor (a white rotter) was investigated. Air dry extracts were dissolved in 60% methanol and impregnated into sapwood blocks of Ceiba pentandra Gaertn. Extract dosages were 8.009, 24.778, 48.056 and 96.11 kg/m3 (0.5, 1.5, 3.0 and 6.0 lb/ft3). Treated blocks were exposed to L. trabea and P. versicolor attack for 14 weeks by the soil block method using the procedure set out in ASTM D 1413-72. Only extract dosages of 48.056 and 96.11 kg/m3 (3.0 and 6.0 lb/ft3) were found efficacious in suppressing fungal attack. A tukey studentized test found both dosages significant at 1% level.