It has been suggested that increasing plant species diversity (PSD) in agroecosystems at different spatiotemporal scales reduces the impacts of crop pests and diseases as well as the dependence on synthetic plant protection products. This principle was applied to a range of tropical case studies. These studies involved various pests and pathogens with contrasting life history traits, different cropping systems (a cereal crop in conservation agriculture, vegetable crops in rotational and trap cropping systems, perennial crops in agroforestry) and various spatial scales of PSD deployment (field and farmscape). Here we review the outcomes of these studies, and discuss the lessons learned regarding synergies and tradeoffs associated with regulation effects provided by PSD. The major points are:

1) results contributed to solve local crop pest and disease problems such as bacterial wilt on tomato in Martinique, scarab beetles and witchweed on upland rice in Madagascar, fruitworms on tomato in Martinique and okra in Niger, fruit flies on cucurbit vegetables in Reunion, mirid bugs and black pod rot on cocoa in Cameroon, berry borer and leaf rust on coffee in Costa Rica;

2) the importance of cross-cutting issues regarding green manure, cover crops or companion plants across case studies at the field scale involving below-ground and aerial processes, were highlighted, particularly that of the within-species genetic variation of these plants;

3) based on the fruitworm/tomato case study, a dynamic and spatially-explicit individual-based model was developed as a generic tool to improve understanding of system functioning by assessing infestation patterns in response to main crop/trap crop relative attractiveness, spatiotemporal deployment of the main crop/trap crop and insect behavioral traits;

4) tradeoffs were highlighted regarding pest and disease complex management, single-option pest and disease control via several pathways based on a single PSD-deployment measure and other ecosystem services and disservices at various scales.

已经提出，在不同的时空尺度上增加农业生态系统中的植物物种多样性（PSD）可以减少农作物病虫害的影响以及对合成植物保护产品的依赖。该原则已应用于一系列热带案例研究。这些研究涉及具有不同生活史特征的各种害虫和病原体，不同的种植系统（保护性农业中的谷类作物，轮作和诱集系统中的蔬菜作物，农林业中的多年生作物）以及PSD部署的各种空间尺度（田间和农场景观） 。在这里，我们回顾了这些研究的结果，并讨论了与PSD提供的调节效果相关的协同作用和取舍方面的经验教训。要点是：

1）研究结果有助于解决当地的农作物病虫害问题，例如马提尼克岛的番茄细菌枯萎，马达加斯加的旱稻米上的金龟子甲虫和魔草，尼日尔的马提尼克岛和秋葵的番茄上的果虫，留尼汪的葫芦类蔬菜上的果蝇喀麦隆的可可粉上有虫子和黑豆腐，哥斯达黎加的咖啡上有浆果蛀虫和叶锈。

2）在涉及地下和空中过程的田间规模的案例研究中，强调了涉及绿肥，覆盖作物或伴生植物的跨领域问题的重要性，特别是这些植物的种内遗传变异问题；

3）基于果虫/番茄案例研究，开发了动态且空间明确的基于个体的模型，作为一种通用工具，通过评估对主要农作物/诱集作物相对吸引力，时空部署的侵染模式，来增进对系统功能的了解主要农作物/圈套作物和昆虫的行为特征；

4）强调了在有害生物和疾病综合管理，通过单一PSD部署措施以及多种规模的其他生态系统服务和破坏基于几种途径的单一选择的有害生物和疾病控制方面的权衡。