Plant lesions affect disease impact, progression and host resistance. Root lesions caused by Armillaria ostoyae (Romagn.) Herink were inspected on 24‐ to 34‐year‐old planted Douglas‐fir (Pseudotsuga menziesii (Mirb.) Franco) pulled from the soil in five locations. Four hundred seventy‐nine lesions were measured for length (mm), expansion rate (mm/year) and lesion type. Lesion types were patch lesions on a root side, girdled lesions covering the root circumference and root collar lesions on the stem below ground. Non‐linear mixed modelling revealed that fungal lesion length at girdled and collar lesions increased but the expansion rate slowed as a power function of time, indicating increasing secondary inoculum and host resistance. Average fungal lesion expansion rate in girdled root and collar lesions was 127 mm the first year which then declined non‐linearly to 26 mm/year after 10 years. Fungal lesion length in patch lesions showed little change after the first year of infection. For girdled and collar lesions, fungal lesion length increased with tree size at the time of infection. Sites with a longer frost‐free period had shorter girdled root and stem lesions, probably because of more active host defence. Results indicate that mortality would be rare from one infection event. Furthermore, patch lesions pose a lower risk of mortality than other lesions because of a lower fungal lesion expansion rate and secondary inoculum. Tree size, lesion position, lesion type and fungal lesion expansion rate need to be considered when assessing the risk of lesions to individual tree survival. Techniques to minimize the disease impact are discussed.

中文翻译：

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花旗松根病菌 Armillaria ostoyae 的真菌病斑长度和扩张率影响根系定植和损伤

植物病变会影响疾病的影响、进展和宿主抗性。在 5 个位置从土壤中拔出的 24 至 34 岁的种植花旗松（Pseudotsuga menziesii (Mirb.) Franco）检查了由蜜环菌（Romagn.）Herink 引起的根部病变。测量了 479 个病灶的长度 (mm)、扩张速度 (mm/年) 和病灶类型。病斑类型为根侧斑块病斑、覆盖根周的环斑病斑和地下茎上的根环病斑。非线性混合模型显示，带状和领状病变处的真菌病变长度增加，但扩张速度随时间的幂函数而变慢，表明二次接种物和宿主抵抗力增加。带状根部和颈圈病变的平均真菌病变扩张率在第一年为 127 毫米，然后在 10 年后非线性下降至 26 毫米/年。在感染的第一年之后，斑块病变中的真菌病变长度几乎没有变化。对于带状和领状病变，真菌病变长度随着感染时树木的大小而增加。无霜期较长的地点有较短的带状根和茎病变，可能是因为宿主防御更活跃。结果表明，一次感染事件很少导致死亡率。此外，由于真菌病灶扩展率和二次接种率较低，斑块病灶比其他病灶具有更低的死亡风险。树的大小，病变位置，在评估病斑对个体树木生存的风险时，需要考虑病斑类型和真菌病斑扩展率。讨论了尽量减少疾病影响的技术。