In grain crops, aphids are important pests, but they can be suppressed by hymenopteran parasitoids. A challenge in incorporating parasitoids into Integrated Pest Management (IPM) programs, however, is that parasitoid numbers can be low during periods within the season when aphids are most damaging. Understanding the population dynamics of key aphid species and their parasitoids is central to ameliorating this problem. To examine the composition and seasonal trends of both aphid and parasitoid populations in south-eastern Australia, samples were taken throughout the winter growing seasons of 2017 and 2018 in 28 fields of wheat and canola. Myzus persicae (Sulzer) was the most abundant aphid species, particularly within canola crops. Across all fields, aphid populations remained relatively low during the early stages of crop growth and increased as the season progressed. Seasonal patterns were consistent across sites, due to climate, crop growth stage, and interactions between these factors. For canola, field edges did not appear to act as reservoirs for either aphids or parasitoids, as there was little overlap in the community composition of either, but for wheat there was much similarity. This is likely due to the presence of similar host plants within field edges and the neighbouring crop, enabling the same aphid species to persist within both areas. Diaeretiella rapae (M’Intosh) was the most common parasitoid across our study, particularly in canola, yet was present only in low abundance at field edges. The most common parasitoid in wheat fields was Aphidius matricariae (Haliday), with field edges likely acting as a reservoir for this species. Secondary parasitoid numbers were consistently low across our study. Differences in parasitoid species composition are discussed in relation to crop type, inter-field variation, and aphid host. The results highlight potential focal management areas and parasitoids that could help control aphid pests within grain crops.

中文翻译：

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澳大利亚谷物生产景观中蚜虫的膜翅类寄生虫

在谷物作物中，蚜虫是重要的害虫，但可以被膜翅目寄生虫抑制。但是，将寄生虫纳入病虫害综合治理（IPM）计划的一个挑战是，在蚜虫危害最大的季节内，寄生虫的数量可能会很低。了解关键蚜虫及其寄生虫的种群动态对缓解这一问题至关重要。为了检查澳大利亚东南部蚜虫和寄生虫种群的组成和季节趋势，在2017年和2018年整个冬季生长季节的28个小麦和油菜中取样。桃蚜（苏尔寿（Sulzer））是最丰富的蚜虫种类，尤其是在双低油菜籽作物中。在所有田间，蚜虫种群在作物生长的早期阶段仍然相对较低，并且随着季节的发展而增加。由于气候，作物生长阶段以及这些因素之间的相互作用，各个地点的季节性模式是一致的。对于双低油菜籽，田间边缘似乎没有充当蚜虫或寄生虫的贮藏库，因为二者的群落组成几乎没有重叠，但对于小麦却有很多相似之处。这很可能是由于田间边缘和邻近作物中存在相似的寄主植物，使相同的蚜虫物种在两个区域内都存在。小菜蛾（M'Intosh）是我们研究中最常见的寄生虫，尤其是在油菜中，但在田间边缘仅以低丰度存在。小麦田中最常见的寄生虫是蚜虫蚜虫（Haliday），田间边缘很可能是该物种的贮藏库。在我们的研究中，次生寄生虫数量一直较低。讨论了类寄生虫种类组成的差异，涉及农作物类型，田间变异和蚜虫寄主。结果突出了潜在的重点管理领域和寄生虫，可帮助控制谷物作物中的蚜虫害虫。