Elliott Norman C, Brewer Michael J, Giles Kristopher L
USDA-ARS Plant Science Research Laboratory, Stillwater, OK.
Texas A&M AgriLife Research, Corpus Christi, Corpus Christi, TX.
Environ Entomol. 2018 Aug 11;47(4):803-811. doi: 10.1093/ee/nvy035.
Winter wheat is Oklahoma's most widely grown crop, and is planted during September and October, grows from fall through spring, and is harvested in June. Winter wheat fields are typically interspersed in a mosaic of habitats in other uses, and we hypothesized that the spatial and temporal composition and configuration of landscape elements, which contribute to agroecosystem diversity also influence biological control of common aphid pests. The parasitoid Lysiphlebus testaceipes (Cresson; Hymenoptera: Aphidiinae) is highly effective at reducing aphid populations in wheat in Oklahoma, and though a great deal is known about the biology and ecology of L. testaceipes, there are gaps in knowledge that limit predicting when and where it will be effective at controlling aphid infestations in wheat. Our objective was to determine the influence of landscape structure on parasitism of cereal aphids by L. testaceipes in wheat fields early in the growing season when aphid and parasitoid colonization occurs and later in the growing season when aphid and parasitoid populations are established in wheat fields. Seventy fields were studied during the three growing seasons. Significant correlations between parasitism by L. testaceipes and landscape variables existed for patch density, fractal dimension, Shannon's patch diversity index, percent wheat, percent summer crops, and percent wooded land. Correlations between parasitism and landscape variables were generally greatest at a 3.2 km radius surrounding the wheat field. Correlations between parasitism and landscape variables that would be expected to increase with increasing landscape diversity were usually positive. Subsequent regression models for L. testaceipes parasitism in wheat fields in autumn and spring showed that landscape variables influenced parasitism and indicated that parasitism increased with increasing landscape diversity. Overall, results indicate that L. testaceipes utilizes multiple habitats throughout the year depending on their availability and acceptability, and frequently disperses among habitats. Colonization of wheat fields by L. testaceipes in autumn appears to be enhanced by proximity to fields of summer crops and semi-natural habitats other than grasslands.
冬小麦是俄克拉荷马州种植最广泛的作物，于9月和10月播种，从秋季生长至春季，并在6月收获。冬小麦田通常散布于其他用途的各种栖息地镶嵌体中，我们推测，有助于农业生态系统多样性的景观要素的时空组成和配置也会影响常见蚜虫害虫的生物防治。寄生蜂淡足蚜小蜂（Cresson；膜翅目：蚜茧蜂科）在降低俄克拉荷马州小麦蚜虫种群数量方面非常有效，尽管人们对淡足蚜小蜂的生物学和生态学了解很多，但仍存在知识空白，限制了对其何时何地能有效控制小麦蚜虫侵扰的预测。我们的目标是确定景观结构对淡足蚜小蜂在小麦田对谷物蚜虫寄生的影响，一是在生长季节早期蚜虫和寄生蜂定殖时，二是在生长季节后期蚜虫和寄生蜂种群在小麦田建立时。在三个生长季节对70块田地进行了研究。淡足蚜小蜂寄生率与斑块密度、分形维数、香农斑块多样性指数、小麦百分比、夏季作物百分比和林地百分比等景观变量之间存在显著相关性。寄生率与景观变量之间的相关性通常在围绕麦田半径3.2公里处最大。寄生率与预期会随景观多样性增加而增加的景观变量之间的相关性通常为正。随后对秋季和春季小麦田淡足蚜小蜂寄生情况的回归模型表明，景观变量影响寄生率，且寄生率随景观多样性增加而增加。总体而言，结果表明淡足蚜小蜂全年利用多种栖息地，具体取决于其可用性和可接受性，并经常在不同栖息地之间扩散。秋季淡足蚜小蜂对麦田的定殖似乎因靠近夏季作物田和除草地之外的半自然栖息地而增强。
