Context Landscape complexity affects herbivores in agroecosystems, but consequences on pest control services are variable. Carryover effects of landscape composition in previous years on herbivore control may be important, but have been seldom assessed. Understanding landscape complexity effects at different temporal and spatial scales is important to improve sustainable pest control services. Objectives We examined the effect of agricultural landscape complexity (e.g., the percentage of semi-natural habitats) on cereal leaf beetle (CLB), Oulema melanopus L., and its parasitism by Tetrastichus julis (Walker). Methods From 2014 to 2015, we assessed CLB abundance and parasitism in 54 fields along a gradient of landscape complexity (2–70% of semi-natural habitats) in southern Alberta. We used generalized linear models to test the effects of percentage of crops and semi-natural habitats, and landscape and crop diversity on CLB abundance and parasitism at 0.5, 1, 1.5 and 2 km spatial scales. Results CLB abundance decreased with higher crop diversity at the 0.5 km scale and increased with CLB host crops in the current and previous years at multiple scales, supporting the resource concentration hypothesis. CLB parasitism increased with CLB abundance and in landscapes with increased canola and alfalfa during a year of low CLB abundance. CLB abundance had contrasting associations with semi-natural habitats: positive with woodlands and negative with pastures. Conclusions Our study suggests that crop diversity reduces the abundance of this specialist pest in agricultural landscapes likely by a dual effect of reducing host crop area and increasing habitats with resources for parasitoids.

中文翻译：

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寄主作物和作物多样性对农业景观中专业食草动物丰度和寄生性的对比影响

背景景观复杂性影响农业生态系统中的食草动物，但对害虫防治服务的影响各不相同。前几年景观组成对食草动物控制的遗留影响可能很重要，但很少被评估。了解不同时空尺度上的景观复杂性影响对于改善可持续的虫害防治服务非常重要。目标 我们研究了农业景观的复杂性（例如，半自然栖息地的百分比）对谷叶甲虫 (CLB)、Oulema melanopus L. 及其寄生的 Tetrastichus julis (Walker) 的影响。方法 从 2014 年到 2015 年，我们评估了艾伯塔省南部沿景观复杂性梯度（半自然栖息地的 2-70%）的 54 个领域的 CLB 丰度和寄生情况。我们使用广义线性模型来测试作物和半自然栖息地的百分比以及景观和作物多样性对 0.5、1、1.5 和 2 公里空间尺度上的 CLB 丰度和寄生的影响。结果 CLB 丰度在 0.5 公里范围内随着作物多样性的增加而降低，而在当前和前几年在多个尺度上随着 CLB 寄主作物的增加而增加，支持资源集中假说。在低 CLB 丰度的一年中，CLB 寄生随着 CLB 丰度和在油菜和苜蓿增加的景观中增加。CLB 丰度与半自然栖息地形成鲜明对比：林地为正，牧场为负。