Recovery and Grades of Eucalyptus urograndis Sawn Timber Infected by Chrysoporthe deuterocubensis Stem Canker Disease

Abstract

Global wood demand continues to rise while supply from natural forests declines, increasing the importance of forest plantations as a sustainable timber source. In Malaysia, Eucalyptus urograndis has gained attention as a fast-growing plantation species, but stem canker disease caused by Chrysoporthe deuterocubensis threatens timber recovery and value. This study evaluated the effect of infection severity on sawn timber recovery, grading, and value in 11-year-old E. urograndis trees from Sabah, Malaysia. Twelve trees were classified into four infection-severity classes, felled, and sawn using a back-sawing pattern. A total of 404 boards were assessed for dimensions, recovery, visual grade, and disease-related defects using modified Malaysian Grading Rules. Board size shifted toward smaller dimensions as infection severity increased. However, total recovery remained relatively high across classes, and severely infected logs produced the highest volume recovery. Healthy trees yielded the greatest proportion of SELECT and STANDARD grade boards, whereas infected trees produced more downgraded boards. Infection severity was not significantly correlated with log diameter or board volume recovery. These findings indicate that infected E. urograndis logs can still provide commercially usable timber, although with reduced product quality and value.