Loss of Merchantable Wood in Radiata Pine Associated with Infection by Diplodia pinea

Abstract

SUMMARY Productivity losses in stands of radiata pine (P. radiata, D.Don) caused by defect associated with infection by the fungal pathogen Diplodia pinea (Deem.) Kickx have been examined. In spite of the high incidence of defect, the effect on the volume and value of the standing crop was minor, except in very heavily affected young stands, where serious problems in the utilization of defective wood are expected. Inoculation experiments carried out in the field and in a controlled greenhouse environment showed that D. pinea could attack the cortex of healthy trees and produce stem kinks, cankers and dead-top that were identical with defects observed in affected stands. A study in a 15-year-old stand, in which about one-fifth of the trees were dead- topped, showed that the growth of the dead-topped trees was reduced by about 40 per cent. A survey in 10-year-old and 17-year-old stands indicated that the incidence of dead top was closely related to topography. Fast growing stands on gully and river flat sites were seriously affected, while stands on higher slopes were relatively unaffected. First thinning had little effect in reducing the level of defect. The influence of moisture stress on the susceptibility of P. radiata to D. pinea infection is briefly discussed.