Field Borders Provide Winter Refuge for Beneficial Predators and Parasitoids: A Case Study on Organic Farms

Assessment of determinants of high nature value (HNV) farmland at plot scale in Western Pyrenees

The concept of High Nature Value (HNV) farming hinges on the causality between agroecosystems with low intensity of management and the corresponding environmental outcomes, including high levels of biodiversity and the presence of semi-natural habitats. Although European strategies for rural development and biodiversity conservation have long recognized the importance of HNV farmlands, many of those areas are currently threatened by intensification and land abandonment. A variety of approaches have been developed for identifying HNV areas and measuring changes in their distribution and extent at landscape scales. In contrast, quantitative approaches for evaluating differences in HNV among the most basic units of management (farms and farm plots) are scarce and almost exclusively based on biodiversity indicators. This gap limits our ability to derive existing gradients of HNV at fine scale and the underlying cause conducive to HNV. Hence, we implemented an index to capture multiple facets of HNV based on expert knowledge criteria and field surveys performed at the finest scale of management (plot). First, we computed this index for hundreds of grasslands located across the Western Pyrenees. Then, we analysed the relationship between the nature value of plots and environmental, management and socio-economic variables. Our results evidence a gradient between low diversity and intensively used agricultural plots and HNV grasslands in the Western Pyrenees. Highest nature values were significantly related to the occurrence of plots in meadows located in steep areas within the Natura 2000 network, whereas lowest values were related to recently opened areas and the number of treatments per year. Importantly, this index, which could be adapted to other farming areas, provides quantitative information to support the implementation of result-based schemes, including eco-schemes and agri-environment-climate interventions of the new CAP (2023-2027).

Plant-Rich Field Margins Influence Natural Predators of Aphids More Than Intercropping in Common Bean

Simple Summary

Field margin plants are important in providing resources for natural enemies (NEs) and improving biological control of crop pests. However, the use of field margin plants for biological control particularly of important common bean pests is understudied in smallholder farming systems of sub-Saharan Africa (SSA). We evaluated the potential of field margin plants with respect to intercropping systems in common bean fields to enhance the population of NEs of common bean pests. We observed a high assemblage of important NEs of common bean pests for some insect taxa with minimal impact of intercropping on NEs. Field margin plants could be managed to provide a wide range of resources to NEs and therefore biological control of common bean pests.

Abstract

Field margins support important ecosystem services including natural pest regulation. We investigated the influence of field margins on the spatial and temporal distribution of natural enemies (NEs) of bean pests in smallholder farming systems. We sampled NEs from high and low plant diversity bean fields using sweep netting and coloured sticky traps, comparing monocropped and intercropped farms. NEs collected from within crops included predatory bugs, lacewings, predatory flies, parasitic flies, parasitic wasps, lady beetles, and a range of other predatory beetles; with the most dominant group being parasitic wasps. Overall, high plant diversity fields had a higher number of NEs than low-diversity fields, regardless of sampling methods. The field margin had a significantly higher number of lacewings, parasitic wasps, predatory bugs, syrphid flies, and other predatory beetles relative to the crop, but beneficial insects were collected throughout the fields. However, we observed marginally higher populations of NEs in intercropping than in monocropping although the effect was not significant in both low and high plant diversity fields. We recommend smallholder farmers protect the field margins for the added benefit of natural pest regulation in their fields.