Peanut and Field Crops Research Unit, USDA-ARS, 1301 N. Western Road, Stillwater, OK 74075, USA.
Department of Entomology and Plant Pathology, Oklahoma State University, 127 Noble Research Center, Stillwater, OK 74078, USA.
J Econ Entomol. 2024 Jun 10;117(3):907-917. doi: 10.1093/jee/toae073.
The number, timing, and fitness of colonizing parasitoids in fields of ephemeral crops often depend on factors external to the fields. We investigated cereal aphid parasitism in 23 winter wheat fields using sentinel plants infested with bird cherry-oat aphids, Rhopalosiphum padi (L.) (Hemiptera: Aphididae), and we investigated the effect of parasitoids on cereal aphid population growth using exclusion and parasitoid-accessible cages infested with bird cherry-oat aphids. Lysiphlebus testaceipes (Cresson) (Hymenoptera: Braconidae), Aphelinus nigritus (Howard) (Hymenoptera: Aphelinidae), and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), in decreasing order of abundance, parasitized R. padi on sentinel plants. The mean percent parasitism in parasitoid-accessible cages was 5.2% in autumn and 35.0% in spring. Aphid population intensity was greater in complete exclusion than in parasitoid-accessible cages. Measures of landscape composition and configuration were quantified, and aphid parasitism in autumn by L. testaceipes and A. nigritus was positively associated with % landcover by summer crops and patch density. Parasitism by both species was negatively associated with contagion and % woodlands. Parasitism during spring was positively associated with % grassland and fractal dimension and negatively associated with % canola. The number of braconid mummies per sentinel plant was positively correlated to the number of braconid mummies on wheat stems from parasitoid-accessible cages. Results indicate that cereal aphid mortality caused by parasitoids and their ability to exert effective biological control is related to landscape structure. Comparing this study to an earlier study in the same agroecosystem demonstrated temporal stability of the landscape influence on aphid parasitism by L. testaceipes in winter wheat.
在短暂生长作物的田地里，寄生性天敌的数量、时间和适合度通常取决于田地里之外的因素。我们使用感染了禾谷缢管蚜（Rhopalosiphum padi）的哨兵植物，调查了 23 个冬麦田中的麦二叉蚜寄生情况，同时还使用了感染禾谷缢管蚜、但可以让寄生性天敌进入的隔离笼和开放笼，调查了寄生性天敌对麦二叉蚜种群增长的影响。在哨兵植物上，按照丰度从高到低，依次为刻腹寄蝇（Lysiphlebus testaceipes）、黑瘤蚜茧蜂（Aphelinus nigritus）和菜蚜茧蜂（Diaeretiella rapae）寄生了禾谷缢管蚜。在开放笼中，秋季和春季的平均寄生率分别为 5.2%和 35.0%。在完全隔离的情况下，蚜虫种群密度大于开放笼。量化了景观组成和配置的各项指标，发现秋季刻腹寄蝇和黑瘤蚜茧蜂对禾谷缢管蚜的寄生率与夏季作物的 % 土地覆盖和斑块密度呈正相关。两种寄生性天敌的寄生率均与蔓延度和 % 林地呈负相关。春季的寄生率与 % 草地、分形维数呈正相关，与油菜籽的 % 呈负相关。每个哨兵植物上的茧蜂蛹数量与开放笼内小麦茎上的茧蜂蛹数量呈正相关。结果表明，寄生性天敌导致的麦二叉蚜死亡率及其实施有效生物防治的能力与景观结构有关。将本研究与同一农业生态系统中的早期研究进行比较，证明了在冬小麦中，刻腹寄蝇的寄生对景观的影响具有时间稳定性。
