Assessment of the effect of Nectria flute canker on wood quality within mature <Emphasis Type="Italic">Pinus radiata</Emphasis> using multiple methods

Nectria flute canker is a fungal disease that results in cankers on Pinus radiata stems. The disease, caused by the pathogen Neonectria fuckeliana, is associated with commercial pruning operations that limit knot defect to a central core to promote growth of high-quality clearwood. Nectria flute canker is present in commercial plantation forests in parts of New Zealand and Chile. Symptoms of the disease, bark cracks, stem flattenings or depressions and flute cankers, were identified on 25 mature Pinus radiata trees. Trees were felled, and discs crosscut from within, and adjacent to, the disease symptoms. The discs were photographed, and three different methods were used to determine the extent of Nectria damage beyond the defect core into the valuable clearwood sheath. These methods included a visual assessment of photographs of internal damage and two quantitative methods, based on calculations of defect extent using image processing software. Overall, flute cankers were associated with the greatest degree of encased bark and severe decay pockets, and stem flattenings the least. None of the flattened stems had internal decay. The average damage to the clearwood sheath due to flute canker was 43%, whilst that for bark cracks and flattenings was 19 and 8%, respectively. Similar results were achieved using all three methods, and the preferred method would depend on the context of the study. Using a combination of all three methods provides a robust method for measuring the damage to internal wood quality by stem pathogens and other abiotic agents.