Copes Warren E
USDA-ARS Thad Cochran Southern Horticulture Laboratory, P.O. Box 287, Poplarville, MS 39470.
Plant Dis. 2015 Jan;99(1):100-105. doi: 10.1094/PDIS-01-14-0033-RE.
The most reliable approach for timing fungicides to control Rhizoctonia web blight on container-grown azalea has been a fixed calendar date. The purpose of this study was to model periods when a preventive control could be applied in advance of significant increases in leaf blight intensity (LBI) in response to a daily accumulated risk value indicating conducive conditions of temperature (18 or more hours between 20 and 30°C when maximum temperature is less than 35°C), leaf wetness (16 or more hours), and/or rainfall (greater than 6.7 mm above the maximum daily irrigation). Analysis used weather measurements taken every 30 minutes from 11 site-year datasets from 2006 to 2011, and weekly or biweekly LBI assessments. Six developmental site-year datasets were analyzed using receiver operating characteristic (ROC) curve procedures to evaluate models. Only a single model predicted true positives and negatives significantly greater than a 50:50 probability. Subsequently, five site-year validation datasets were evaluated. Similar results were obtained from both the developmental and validation datasets, which produced ROC areas of 0.7715 (P = 0.0120) and 0.8393 (P = 0.0034), respectively. The practical application of weather-based forecasting for management of web blight in nurseries is discussed.
在容器栽培的杜鹃花上，通过固定日历日期来确定杀菌剂防治丝核菌叶枯病的最佳时机是最可靠的方法。本研究的目的是根据每日累积风险值建立模型，预测在叶枯病严重程度（LBI）显著增加之前进行预防性防治的时期，该风险值表明温度（最高温度低于35°C时，20至30°C之间有18小时或更长时间）、叶片湿度（16小时或更长时间）和/或降雨量（高于每日最大灌溉量6.7毫米以上）等有利条件。分析使用了2006年至2011年11个地点年份数据集每30分钟采集的气象数据，以及每周或每两周进行的LBI评估。使用接受者操作特征（ROC）曲线程序对六个发育地点年份数据集进行分析，以评估模型。只有一个模型预测的真阳性和真阴性显著大于50:50的概率。随后，对五个地点年份验证数据集进行了评估。发育数据集和验证数据集都得到了相似的结果，其ROC面积分别为0.7715（P = 0.0120）和0.8393（P = 0.0034）。本文还讨论了基于天气的预测在苗圃叶枯病管理中的实际应用。
