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Arable crops ecosystems - habitat diversification, crop management and natural enemies for crop protection and biodiversity - IF0126

Eighty percent of our land is farmed and farmland biodiversity has declined significantly as a consequence of agricultural intensification over the last 40 years. Biodiversity is now acknowledged as an essential component of sustainable development (England biodiversity strategy: Annual stock take 2003-2004, Defra, 2005) and today, the role of farming in protecting and managing our natural resources, while also remaining economically viable, is a serious challenge to the industry. Reform of the Common Agricultural Policy (CAP) and adoption of ‘The Strategy for Sustainable Farming and Food - Facing the Future’ (Defra, 2002) has ‘decoupled’ support payments from production and instead rewards farmers for their environmental management practices, making them part of the solution – and not part of the problem. Farmers now receive a single farm payment linked, through cross compliance, to environmental management. There is an Entry Level Stewardship scheme (ELS) open to all farmers and aimed at rolling out basic biodiversity benefits on a high proportion of farmland. A Higher Level Stewardship scheme (HLS) is targeted at more specific environmental management options and so is likely to be taken up by fewer farmers but could deliver greater biodiversity benefits. In addition, from 2005, set-aside can comprise up to 8% of the cropped land and farmers may, therefore, be encouraged to take further land out of conventional crop production. Within the new stewardship schemes this set-aside land can be managed for biodiversity by planting with mixtures to support invertebrates, birds, pollinators and mammals or sown to non-food alternative crops in line with ‘A Strategy for non-food crops and uses – Creating value from renewable materials’ (Defra, 2004). As the use of agrienvironment schemes and the planting of non-food crops increases, so the mosaic of habitats in our farm landscape will become more diverse. This represents a significant opportunity to achieve additional environmental benefits with respect to ecosystem services such as pest management. This project will consider the role of habitat (crop and non-crop) diversity, scale and distribution on aphid pest management in arable crops.

Natural enemies (parasitoids, predators and pathogens) of pests are a vital component of the functional biodiversity on farmland and deliver an important pest management service that is central to sustainable farming systems. Research has demonstrated that habitat manipulation and diversification can increase populations of individual natural enemy species/ groups with pest control potential (e.g. Thomas et al., 1991; Marshall & Moonen, 2002; Powell and Pickett, 2003; Ekesi et al., 2005). For example field margins can significantly contribute to the efficiency of natural biological control of aphid pests by parasitoids and syrphids, particularly in cereals (Powell et al., 2004; ((LK0915) ‘3D Farming – Making biodiversity work for the farmer’) and several field margin and hedgerow plants with potential as sources of beneficial aphid-pathogenic fungi, particularly Pandora neoaphidis have been identified (Shah et al., 2004; (LK1159) ‘Novel strategies for aphid control using entomopathogenic fungi’). However, for many pests a diverse natural enemy community is essential to ensure reliable pest management in the long term (Defra-funded project AR0318). In this project we will determine how increasing habitat complexity on arable farms, (the juxtaposition of field margins, non-food crops and arable crops within a farmland mosaic), can be optimised to enhance and maintain the species richness and diversity of natural enemy communities and, thereby, improve their pest management potential.

Specifically we will test hypotheses in a series of replicated experiments at increasing spatial scales (from the laboratory to mesocosms) using model natural enemy communities for which we have substantial existing data. By manipulating habitat complexity (crop and non-crop plant diversity, alternative host availability, nectar availability) we will provide evidence to identify optimal levels of habitat diversity necessary to enhance natural enemy diversity and co-existence and provide robust pest management. Cereals and their associated aphids will be the model arable crop we use in all experiments and borage and nettles will be our model non-food crops as they provide nectar/ alternative early season hosts respectively. In order to extend interpretation to the field scale and determine the scale, distribution and diversity of field margin habitats necessary to support within-crop natural enemy diversity and cereal aphid control we will sample in arable crops associated with established field margins of contrasting complexity.

This research will provide the evidence base necessary to optimise management of the evolving habitat mosaic within arable landscapes to enhance natural enemy diversity and hence improve natural pest suppression. This will reduce the necessity for insecticide inputs in arable food crop production (e.g. cereals) helping farmers to become net positive contributors to the environment and reduce the environmental footprint of food production substantially. This has clear significance for sustainable food production and security.

O1. Measure the effect of increasing habitat diversity on intra-guild interactions amongst aphid natural enemies, using mesocosm studies. Hypothesis to be tested: Increasing habitat diversity in arable crop ecosystems increases the stability and persistence of natural enemy communities by reducing negative intra-guild interactions.

O2. Measure the effects of the scale and spatial distribution of a range of managed non-crop habitats on the natural enemy community and its impact on aphid pest management on arable farmland. Hypothesis to be tested: The impact of natural enemies on aphid crop pest populations can be enhanced by the presence of non-crop habitats, managed to provide natural enemy resources.

O3. Determine the potential value of non-food crops for increasing natural enemy abundance and diversity and thereby enhancing pest management ecosystem services in arable crop ecosystems. Hypothesis to be tested: Some non-food crops can increase natural enemy abundance and diversity within arable crop ecosystems by providing valuable host/ food resources.
Project Documents
• FRP - Final Report : SID5 IF0126   (1468k)
Time-Scale and Cost
From: 2007

To: 2011

Cost: £1,030,145
Contractor / Funded Organisations
Rothamsted Research (BBSRC)
Arable Farming              
Biological Control              
Integrated Farming Systems              
Sustainable Farming and Food Science              
Sustainable Farming Systems