Phytophthora pluvialis and Phytophthora kernoviae are the causal agents of important needle diseases on Pinus radiata in New Zealand. Little is known about the epidemiology of the diseases, making the development of control strategies challenging. To investigate the seasonality and climatic drivers of sporulation, inoculum traps, consisting of pine fascicles floating on water in plastic containers, were exchanged fortnightly at five sites in P. radiata plantations between February 2012 and December 2014. Sections of needle baits were plated onto selective media and growth of Phytophthora pluvialis and P. kernoviae recorded. To explore the generalizability of these data, they were compared to detection data for both pathogens from the New Zealand Forest Health Database (NZFHDB). Further, equivalent analyses on infection of Rhododendron ponticum by P. kernoviae in Cornwall, UK allowed the comparison of the epidemiology of P. kernoviae across different host systems and environments. In New Zealand, inoculum of P. pluvialis and P. kernoviae was detected between January–December and March–November, respectively. Inoculum of both species peaked in abundance in late winter. The probability of detecting P. pluvialis and P. kernoviae was greater at lower temperatures, while the probability of detecting P. pluvialis also increased during periods of wet weather. Similar patterns were observed in NZFHDB data. However, the seasonal pattern of infection by P. kernoviae in the UK was the opposite of that seen for sporulation in New Zealand. Phytophthora kernoviae was likely limited by warmer and drier summers in New Zealand, but by colder winter weather in the UK. These results emphasize the importance of considering both environmental drivers and thresholds in improving our understanding of pathogen epidemiology.

中文翻译：

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天气变量和季节对雨生疫霉和克氏疫霉孢子形成的影响

雨生疫霉和 Phytophthora kernoviae 是新西兰辐射松重要针叶病的病原体。人们对这些疾病的流行病学知之甚少，这使得控制策略的制定具有挑战性。为了调查孢子形成的季节性和气候驱动因素，2012 年 2 月至 2014 年 12 月期间，在辐射松种植园的五个地点每两周更换一次由漂浮在塑料容器中的松树束组成的接种陷阱。记录了雨生疫霉和 P. kernoviae 的培养基和生长。为了探索这些数据的普遍性，将它们与新西兰森林健康数据库 (NZFHDB) 中两种病原体的检测数据进行了比较。更多，对英国康沃尔郡 P. kernoviae 对杜鹃花感染的等效分析允许对不同宿主系统和环境中 P. kernoviae 的流行病学进行比较。在新西兰，分别在 1 月至 12 月和 3 月至 11 月期间检测到 P. pluvialis 和 P. kernoviae。两种物种的接种量在冬末达到高峰。在较低温度下检测到 P. pluvialis 和 P. kernoviae 的概率更高，而在潮湿天气期间检测到 P. pluvialis 的概率也增加。在 NZFHDB 数据中观察到类似的模式。然而，英国的 P. kernoviae 感染的季节性模式与新西兰的孢子形成模式相反。克氏疫霉可能受到新西兰温暖干燥的夏季的限制，但由于英国较冷的冬季天气。这些结果强调了在提高我们对病原体流行病学的理解方面考虑环境驱动因素和阈值的重要性。