Walnut (Juglans regia) can be affected by several diseases. Among them, walnut blight (WB) which is caused by the bacterium Xanthomonas arboricola pv. juglandis (Xaj) and brown apical necrosis (BAN) which has lately become economically significant causing crop losses in recent years. BAN can be considered as a complex disease in which, besides Xaj, the fungal genera Fusarium and Alternaria could be also involved. The objective of the present work was to determine the occurrence of Xaj and Alternaria sp.-grps. at different phenological stages of walnut in order to provide knowledge about the epidemiological aspects of BAN. Xaj was detected at 9 of the 11 phenological stages under study and Alternaria at all stages. No Fusarium isolates were detected at any stage. Buds were the main hibernation site for the bacterium which showed higher epiphytic concentrations than isolates of Alternaria. However, the fungus was more frequently found at all phenological stages until fruit set. On diseased fruits, the bacterium was predominant and the fungus was only found sporadically. This work provides knowledge that can contribute to the improvement of preventive programs such as control strategies that consider the weather forecasts and the phenology of walnut instead of strategies based on fix calendars.

核桃（Juglans regia）可能会受到多种疾病的影响。其中，核桃枯萎病（WB）是由Xanthomonas arboricola pv .细菌引起的。胡桃木（Xaj）和棕色顶端坏死（BAN）近年来已变得具有重大经济意义，导致农作物损失。BAN 可以被认为是一种复杂的疾病，除了Xaj之外，镰刀菌属和链格孢属真菌也可能参与其中。目前工作的目的是确定Xaj和链格孢属的发生情况sp.-grps。核桃的不同物候阶段，以便提供有关 BAN 流行病学方面的知识。Xaj在所研究的 11 个物候阶段中的 9 个阶段均检测到，而链格孢属则在所有阶段均检测到。在任何阶段均未检测到镰刀菌分离株。芽是该细菌的主要冬眠部位，其附生浓度高于链格孢属分离株。然而，这种真菌在坐果之前的所有物候阶段都更常见。在患病的水果上，细菌占主导地位，真菌仅偶尔存在。这项工作提供的知识有助于改进预防计划，例如考虑天气预报和核桃物候的控制策略，而不是基于固定日历的策略。