Biofuel plants as refugia for pest biocontrol agents

Abstract

Agriculture faces multiple global challenges including climate change, food production, fuel security and insect pest management. Agroecology can provide mitigating solutions to these issues such as using Miscanthus x giganteus (Mxg) shelterbelts on farms. These shelterbelts can provide at least 15 ecosystem services (ES) on commercial dairy farms with centre pivot systems. However, there has been little research that investigates how Mxg shelterbelts could contribute to agricultural functional biodiversity and insect pest management. The former is being degraded by intensive farm management resulting in simplified food webs. This severely inhibits the ES that agroecosystems can provide, such as biological control. This study investigated what potential generalist soil-surface dwelling biological control agents (BCA) use Mxg shelterbelts as refugia compared to a field margin, using pitfall traps during April (early autumn), August (late winter) and September (early spring) 2015. Furthermore, the effectiveness of these potential BCA at consuming a soil-surface active pest was determined using facsimile prey. Additionally, potential BCA that consumed the prey were confirmed using infrared cameras and Sanger sequencing using specific primers for the CO1 mitochondrial gene. Sanger sequencing was conducted on DNA from slugs, the European harvestman (Phalangium opilio), centipedes, predatory beetles and Dicyrtoma fusca. Based on the pitfall trap results, there were distinct potential BCA communities and similar potential BCA richness between Mxg shelterbelts and the field margin. Total facsimile prey consumption was 57 % higher in Mxg shelterbelts. Furthermore, Phalangium opilio and slugs such as Deroceras reticulatum, were confirmed to consume the facsimile prey using video analysis and DNA sequencing but only in Mxg shelterbelts. These findings suggest slugs could potentially be used as BCA in the presence of Mxg shelterbelts. Additionally, an introduced collembolan species Dicyrtoma fusca was found in the field margin on the facsimile prey. This is the first authenticated record of this species in the southern hemisphere but its role in New Zealand agroecosystems is unknown. As a world first, these results indicate that Mxg shelterbelts are refugia for potential BCA and could be implemented in insect pest management using conservation biological control in agroecosystems. Further research needs to further elucidate potential BCA predation rate and community dynamics over a longer study period and whether potential BCA emigrate from the Mxg shelterbelt into the fields in spring. Additionally, further investigation of slugs as potential biocontrol agents is required and the trade-off between this ES and potential ecosystem dis-services (EDS).