Weed maps created late in the growing season are potentially useful in regions where late maturing weeds are problematic and need to be controlled before they produce seed. The objectives of this study were to (1) spatially characterize the population dynamics of predominant weed species and apply this information into quantifying the effect of treated and untreated weed infestations on wheat (Triticum aestivum L.) yields and (2) evaluate potential herbicide savings with post-harvest site-specific treatments. Multi-year grain yield and weed data were acquired at harvest in each of four years (2015–18) within a dryland production field (9.2 ha) in eastern Oregon. Abundance of weed species (2015) and percent cover of weed species (2016, 2017 and 2018) were visually estimated on a square grid based on dividing the field into 7-m² cells. Spatial patterns in the weed community were subject to rapid change and depended on year, crop and weed control strategy. While tumble mustard (Sisymbrium altissimum) was the most predominant and competitive species, the spatial distribution of this weed and that of other species varied each year. Tumble mustard and prickly lettuce (Lactuca serriola) were equally problematic in spring wheat and winter wheat whereas Russian thistle (Salsola tragus) was problematic in spring wheat and downy brome (Bromus tectorum) in winter wheat. Potential savings from site-specific herbicide application varied from 10 to 95% based on percentage of field infested. Weed maps at harvest are useful for studying weed dynamics, identifying potentially herbicide-resistant weeds and planning site-specific weed management. Combined with yield maps, weed maps at harvest are also useful for explaining crop yield variability that is associated with weed competition and weed control in furtherance of integrated weed management strategies.

在生长季节后期创建的杂草图在晚熟杂草有问题并且需要在它们产生种子之前进行控制的地区可能有用。本研究的目的是 (1) 在空间上表征主要杂草物种的种群动态，并将这些信息应用于量化处理和未处理的杂草侵染对小麦 ( Triticum aestivumL.) 产量和 (2) 评估收获后特定地点处理的潜在除草剂节省量。在俄勒冈州东部的旱地生产田（9.2 公顷）中，每四年（2015-18 年）在收获时获得多年粮食产量和杂草数据。杂草种类的丰富度（2015 年）和杂草种类的覆盖率（2016 年、2017 年和 2018 年）在方形网格上基于将田地划分为 7 米^{2 的}单元格进行视觉估计。杂草群落的空间格局会发生快速变化，并取决于年份、作物和杂草控制策略。虽然芥菜 ( Sisymbrium altissimum ) 是最主要和最具竞争力的物种，但这种杂草和其他物种的空间分布每年都在变化。翻滚芥末和多刺的生菜（Lactuca serriola ) 在春小麦和冬小麦中同样存在问题，而俄罗斯蓟 ( Salsola tragus ) 在春小麦中存在问题，而霜雀 ( Bromus tectorum ) 在冬小麦中存在问题。根据田间受侵染的百分比，特定地点施用除草剂的潜在节约范围从 10% 到 95% 不等。收获时的杂草图可用于研究杂草动态、识别潜在的抗除草剂杂草和规划特定地点的杂草管理。结合产量图，收获时的杂草图也可用于解释与杂草竞争和杂草控制相关的作物产量变异性，以促进综合杂草管理策略。