Available at: https://digitalcommons.calpoly.edu/theses/219
Date of Award
MS in Forestry Sciences
Natural Resources Management
This study was a part of the international collaborative IMPACT project, which aims to address the potential threat that the pitch canker disease poses to the use of Pinus radiata D. Don in plantations in New Zealand, Australia, and Chile. A field trial of 264 seedstocks was planted adjacent to a native stand of pitch canker infected P. radiata on the central coast of California, and disease symptom development was recorded over a period of 3 years. The results did not correlate with a greenhouse study of the same seedstocks inoculated with Fusarium circinatum Nirenberg & O'Donnell, the causal agent of pitch canker. Three main types of symptoms were identified (branch flagging, pitchy buds, and chlorotic tips), and preliminary isolation analyses suggest that the disease observed is actually caused by Diplodia pinea (Desm.) Kickx. Survival analysis showed that the effect of tree genetic origin was significant to its time to disease, and that spatial location in the plantation was also significant. Average nearest neighbor analysis showed disease distribution to be significantly clustered, which also suggests that the disease is not pitch canker, but diplodia blight. This experiment illustrates the difficulty in performing naturally infected field trials when another similar-looking fungal disease is also present. It also provides data on seedstock resistance to diplodia blight, another fungal disease important to P. radiata forest managers.