Scott Jason B, Gent David H, Pethybridge Sarah J, Hay Frank S
Tasmanian Institute of Agriculture (TIA), University of Tasmania-Cradle Coast Campus, Burnie, Tasmania, 7320, Australia.
United States Department of Agriculture-Agricultural Research Service, Forage Seed and Cereal Research Unit, Oregon State University, Department of Botany and Plant Pathology, Corvallis 97331.
Plant Dis. 2014 Feb;98(2):267-274. doi: 10.1094/PDIS-07-13-0692-RE.
Sclerotinia crown rot, caused by Sclerotinia minor and S. sclerotiorum, is a disease of pyrethrum in Australia that may cause substantial decline in plant density. The spatiotemporal characteristics of the disease were quantified in 14 fields during three growing seasons. Fitting the binary power law to disease incidence provided slope (b = 1.063) and intercept (ln(A) = 0.669) estimates significantly (P ≤ 0.0001) greater than 1 and 0, respectively, indicating spatial aggregation at the sampling unit scale that was dependent upon disease incidence. Covariate analyses indicated that application of fungicides did not significantly influence these estimates. Spatial autocorrelation and spatial analysis by distance indices indicated that spatial aggregation above the sampling unit scale was limited to 20 and 17% of transects analyzed, respectively. The range of significant aggregation was limited primarily to neighboring sampling units only. Simple temporal disease models failed to adequately describe disease progress, due to a decline in disease incidence in spring. The relationships between disease incidence at the scales of individual plants within quadrats and quadrats within a field was modeled using four predictors of sample size. The choice of the specific incidence-incidence relationship influenced the classification of disease incidence as greater than or less than 2% of plants, a provisional commercial threshold for fungicide application. Together, these studies indicated that epidemics of Sclerotinia crown rot were dominated by small-scale aggregation of disease. Larger scale patterns of diseased plants, when present, were associated with severe disease outbreaks. The spatial and temporal analyses were suggestive of disease epidemics being associated with localized primary inoculum and other factors that favor disease development at a small scale.
由小核盘菌和核盘菌引起的核盘菌冠腐病是澳大利亚除虫菊的一种病害，可能导致植株密度大幅下降。在三个生长季节中，对14个田地该病的时空特征进行了量化。将二元幂律拟合到发病率上，得到的斜率（b = 1.063）和截距（ln(A) = 0.669）估计值分别显著大于1和0（P ≤ 0.0001），这表明在采样单元尺度上存在空间聚集现象，且这种聚集取决于发病率。协变量分析表明，施用杀菌剂对这些估计值没有显著影响。空间自相关和距离指数空间分析表明，采样单元尺度以上的空间聚集分别仅限于所分析样带的20%和17%。显著聚集的范围主要仅限于相邻的采样单元。由于春季发病率下降，简单的时间病害模型未能充分描述病害进展情况。使用四个样本量预测因子对样方内单株尺度和田间样方尺度的发病率之间的关系进行了建模。特定发病率-发病率关系的选择影响了发病率分类为大于或小于植株的2%，这是杀菌剂施用的暂定商业阈值。这些研究共同表明，核盘菌冠腐病的流行以病害的小规模聚集为主。当存在时，患病植株的较大尺度模式与严重病害爆发有关。时空分析表明，病害流行与局部初始接种体以及其他有利于小尺度病害发展的因素有关。
