Pathogen dynamics in agroforestry systems result from several mechanisms and interactions whose independent effects are difficult to delineate. In recent decades, it has been shown that shade, as a structural feature in agroforestry systems, influences the spread of pathogens through its physical and biological effects. In Cameroon, citrus trees are mainly grown in cocoa-based agroforestry systems (CBAS), and are threatened by a variety of pathogens. This study examines how shading modifies the microclimate in the local environment of citrus trees in CBAS, and the resulting effect on citrus foot rot disease (PFRD). The study was conducted in the Cameroon agroecological zone with bimodal rainfall, where a network of 20 CBAS plots was established. Primary cartographic and structural data were used to perform static simulations with cumulative shadow overlay in ShadeMotion software. A soil sensor was used to quantify the microclimate by measuring air temperature and relative humidity above and in the soil, as well as soil pH. Relationships between shade rate, microclimatic variables, and PFRD intensity were investigated. Results showed that the effect of temperature on PFRD was independent of shade rate. A dependency relationship between relative humidity above and in the soil and PFRD according to shade rate was found. Indeed, a positive correlation of PFRD with relative humidity was observed for citrus trees located in full sunlight, while a negative correlation was observed for citrus trees located under dense and light shade. Optimization of structural characteristics of CBAS would allow ecological management of PFRD and reduction in the use of chemical pesticides.

农林业系统中的病原体动态是由多种机制和相互作用造成的，其独立影响很难描述。近几十年来，研究表明，遮荫作为农林复合系统的一个结构特征，通过其物理和生物效应影响病原体的传播。在喀麦隆，柑橘树主要种植在以可可为基础的农林复合系统（CBAS）中，并受到多种病原体的威胁。本研究探讨了遮荫如何改变 CBAS 柑橘树当地环境的小气候，以及由此产生的对柑橘根腐病 (PFRD) 的影响。该研究在喀麦隆双峰降雨农业生态区进行，该地区建立了由 20 个 CBAS 地块组成的网络。主要制图和结构数据用于在 ShadeMotion 软件中通过累积阴影叠加进行静态模拟。土壤传感器通过测量土壤上方和土壤中的空气温度和相对湿度以及土壤 pH 值来量化微气候。研究了遮荫率、微气候变量和 PFRD 强度之间的关系。结果表明，温度对 PFRD 的影响与遮光率无关。发现了土壤上方和土壤中的相对湿度与 PFRD 与遮荫率之间的依赖关系。事实上，对于位于充足阳光下的柑橘树，观察到 PFRD 与相对湿度呈正相关，而对于位于浓密和浅树荫下的柑橘树，观察到 PFRD 与相对湿度呈负相关。CBAS 结构特征的优化将有助于对 PFRD 进行生态管理并减少化学农药的使用。