Assessing the potential of invertebrate natural enemies of insect pests inhabiting <i>Miscanthus</i> x <i>giganteus</i> shelterbelts in pasture

<i>Miscanthus</i> x <i>giganteus</i> (<i>Miscanthus</i>) grass shelterbelts can deliver multiple ecosystem services on New Zealand commercial dairy farms. However, there has been little investigation into how these shelterbelts contribute to insect pest management. Here, on a Canterbury dairy farm, we investigated what generalist surface-dwelling invertebrate natural enemies of insect pests inhabit three separate <i>Miscanthus</i> shelterbelts compared to three unmanipulated field margin plots. The potential contribution of these natural enemy assemblages to future biological control was also investigated. To measure this, live moth egg baits with associated pitfall trapping were deployed in autumn, winter and spring of 2015. <i>Miscanthus</i> and the field margin plots were found to have similar potential natural enemy richness but differed in their community composition. The potential predation rate of pests in <i>Miscanthus</i> was 85% higher than in the field margin. Infrared video and Sanger sequencing confirmed that the harvestman <i>Phalangium opilio</i> and the slug <i>Deroceras reticulatum</i> consumed the egg baits in <i>Miscanthus</i>. Conversely, no bait-consuming invertebrates were identified in the field margin. These preliminary results indicate potential natural enemies inhabit <i>Miscanthus</i> and may consume insect pest eggs on the soil-surface. However, to achieve anyinsect pest suppression, further habitat manipulation would be required.巨芒草（Miscanthus × giganteus，下称芒草）防风林可为新西兰商业奶牛场提供多种生态系统服务功能。然而，目前针对此类芒草防风林在害虫治理中所发挥作用的相关研究仍较为匮乏。本研究于坎特伯雷地区的一座商业奶牛场开展，对比了三处独立的芒草防风林与三处未受人为干预的田边样地中栖息的害虫广食性地表无脊椎天敌类群，并探究了此类天敌群落对未来生物防治的潜在贡献。为开展相关量化研究，研究人员于2015年秋、冬、春三季，布设了活体蛾卵诱饵并结合陷阱诱捕法进行采样。结果显示，芒草防风林与田边样地的潜在天敌类群丰富度相近，但二者的群落组成存在显著差异。芒草生境中害虫的潜在捕食率较田边样地高出85%。通过红外视频成像与桑格测序（Sanger sequencing）分析，确认收割盲蛛（Phalangium opilio）与网纹蛞蝓（Deroceras reticulatum）取食了芒草生境中的卵诱饵；反观田边样地，则未发现任何取食诱饵的无脊椎动物。本项初步研究结果表明，芒草生境中栖息有潜在害虫天敌类群，且可取食地表的害虫卵粒。但要实现有效的害虫种群抑制，仍需开展进一步的生境调控措施。