Abstract：
Methods for causal inference from observational data are common in human disease epidemiology and social sciences but are used relatively little in plant pathology. We draw upon an extensive data set of the incidence of hop plants with powdery mildew (Podosphaera macularis) collected from yards in Oregon during 2014 to 2017 and associated metadata on grower cultural practices, cultivar susceptibility to powdery mildew, and pesticide application records to understand variation in and causes of growers\' fungicide use and associated costs. An instrumental causal forest model identified growers\' spring pruning thoroughness, cultivar susceptibility to two of the dominant pathogenic races of P. macularis, network centrality of a yards during May-June and June-July time transitions, and the initial strain of the fungus were important variables determining the number of pesticide active constituents applied by growers and the associated costs they incurred in response to powdery mildew. Exposure-response function models fit after covariate weighting indicated both the number of pesticide active constituents applied and their associated costs scaled linearly with the seasonal mean incidence of plants with powdery mildew. While the causes of pesticide use intensity are multifaceted, biological and production factors collectively influence the incidence of powdery mildew, which has a direct exposure-response relationship on the number of pesticide active constituents that growers apply and their costs. Our analyses point to several potential strategies for reducing pesticide use and costs for management of powdery mildew on hop. We also highlight the utility of these methods for causal inference in observational studies.
摘要：
从观察数据中推断因果的方法在人类疾病流行病学和社会科学中很常见，但在植物病理学中却很少使用。我们利用了2014年至2017年从俄勒冈州的院子里收集的带有白粉病的啤酒花植物（Podosphaeramacularis）的发病率的广泛数据集，以及有关种植者文化习俗的相关元数据。品种对白粉病的敏感性，和农药施用记录，以了解种植者杀菌剂使用的变化和原因以及相关成本。工具性因果森林模型确定了种植者的春季修剪彻底性，品种对两个主要致病品种的易感性。在5月至6月和6月至7月的时间转换期间，一个码的网络中心性，真菌的初始菌株是重要的变量，决定了种植者施用的农药活性成分的数量以及它们因白粉病而产生的相关成本。在协变量加权后拟合的暴露响应函数模型表明，施用的农药活性成分的数量及其相关成本与白粉病植物的季节性平均发病率成线性比例。虽然农药使用强度的原因是多方面的,生物和生产因素共同影响白粉病的发病率，这对种植者应用的农药活性成分的数量及其成本具有直接的暴露-反应关系。我们的分析指出了减少农药使用和管理啤酒花白粉病的成本的几种潜在策略。我们还强调了这些方法在观察性研究中用于因果推断的实用性。
