Stem volume loss due to severe Diplodia infection in a young Pinus radiata stand.
In a 6-yr-old stand (Tarawera Forest) 14% of the trees were lightly, 22% moderately and 64% heavily infected by D. pinea. Most of the heavily infected trees were also badly malformed. Only 6% were acceptable for harvesting under the limitation of a min. 3.7 m defect-free butt log as specified by a pulp mill. Mean height and diam. of the trees were inversely related to infection levels and thus the degree of malformation. Total vol. of the stand was estimated to be 17 m3/ha, merchantable vol. 10 m3/ha, and the potential merchantable vol. (in the absence of infection) 27 m3/ha. A reduction of 63% in potential merchantable vol. was thus estimated. These results represent an extremely severe case of tree malformation in a localised area.<new para>ADDITIONAL ABSTRACT:<new para>In a 6-yr-old stand in Tarawera Forest, New Zealand, 64% of the trees were heavily infected (over 50% dieback) and badly malformed by D. pinea. Total stand vol. was estimated at 17 m3/ha, merchantable vol. [including pulpwood in defective stems] at 10 m3/ha and potential merchantable vol. at 27 m3/ha giving a reduction of 63% through disease. Only 6% of trees met the harvesting requirement (min. 3.7 m defect-free butt log) of a local pulp and paper mill. This severe case is from a locality notorious for D. pinea infection and is not typical of the whole forest.