Entomopathogenic fungi are increasingly considered for use as biological control agents. However, their effects in tripartite systems involving plants, herbivorous insects, and endophytic fungi remain context dependent and poorly understood. In this study, we tested the hypothesis that inoculation of barley with the entomopathogenic fungus Akanthomyces muscarius affects the biomass of aphids feeding on the plants and influences barley seedling size at early developmental stages. Seedling apical meristems of two barley cultivars, Golden Promise (GP) and Laureate (L), were inoculated with the fungus and subsequently exposed to feeding by the bird cherry-oat aphid Rhopalosiphum padi. Plant dry biomass and total aphid biomass per plant were measured at the end of the experimental period. Inoculation with A. muscarius did not significantly reduce total aphid biomass on either barley cultivar. By contrast, fungal inoculation significantly reduced seedling dry biomass in GP, whereas no such effect was detected in L. Linear mixed-effects modelling revealed significant effects of cultivar, inoculation, and their interaction on plant biomass, indicating cultivar-dependent plant responses to fungal colonisation. Total aphid biomass was significantly affected by cultivar but showed no consistent response to fungal inoculation. This study provides a controlled evaluation of a barley-A. muscarius-aphid tripartite system and highlights cultivar-specific outcomes of fungal inoculation under aphid feeding pressure.

1. Bacterial endosymbionts can increase aphid tolerance to environmental stressors, including natural enemies, but the mechanisms remain unclear. Macrosiphum euphorbiae, which frequently feeds on Solanum species, forms a facultative association with Hamiltonella defensa. 2. Parasitoid wasps use volatile cues from aphid honeydew to locate hosts, yet the role of endosymbionts in shaping honeydew attractiveness to parasitoids has been little studied. 3. We compared honeydew production from clonal lines of M. euphorbiae with and without H. defensa across two aphid genotypes, collecting and analysing the composition of volatile organic compounds (VOCs) and testing parasitoid (Aphidius ervi) behavioural responses to honeydew presented in a choice assay. 4. Honeydew production differed between genotypes, and H. defensa-infected aphids produced more honeydew in the choice assay. Parasitoids were more attracted to honeydew from infected aphids, although VOC profiles showed minimal differences between infected and uninfected aphids. 5. These results suggest that facultative endosymbionts may influence aphid honeydew production and indirectly affect parasitoid foraging, highlighting the importance of mechanistic studies of symbiont-mediated tritrophic interactions.

Although cover crops can potentially improve on-farm soil and water management to reduce erosion, their ability to bind soil and whether multi-species cover crops offer additional benefits has attracted little attention. This study aimed to assess the impact of cover crop diversity (Secale cereale, Brassica juncea, Vicia faba as monocultures and mixtures) on soil loss through changes in root-soil binding using rhizosheath mass an indicator in a silt loam field near Dundee, Scotland. Using a randomized block design, overland flow simulations (8 L min−1) tested soil loss across treatments, and soil cores were collected for rhizosheath and root measurements. Shoots were removed from half of the plots prior to measurements to isolate root diversity effects. Individual species identity, rather than species diversity, determined root and rhizosheath mass, with treatments containing V. faba having 64 % more root mass than the other species, and treatments containing S. cereale having 50 % more rhizosheath mass per unit of root dry mass than others. Shoot presence delayed runoff, but neither rhizosheath mass nor species diversity affected soil loss. Between-block variation in sediment concentration, total sediment and total runoff suggested that soil loss was influenced more by intra-field variability in soil structural and hydraulic properties. This work highlights how intra-field variability in soil structural and hydraulic properties can critically influence the success of erosion control measures, offering valuable guidance for future research and practical application of site-specific strategies for conserving soil function.

The potato aphid Macrosiphum euphorbiae is one of many polyphagous crop pests involved in the transmission of insect-vectored pathogens. While their North American counterparts reproduce via cyclical parthenogenesis, UK populations of M. euphorbiae appear to persist asexually, resulting in the maintenance of several genotypes, with some demonstrating genotype-specific traits; this includes innate resistance to parasitism from the hymenopterous parasitoid wasp Aphidius ervi. The genetic and molecular basis for genotype-specific traits is often unknown. Here we present a chromosome scale assembly for a parasitoid-resistant clonal line of M. euphorbiae and provide insights into the genotypic composition and distribution of UK potato aphid populations using microsatellite and whole-genome sequencing (WGS) techniques, focusing on geographically separated potato crops within two distinct areas of the UK (Merseyside and Tayside). We show that the genome consists of five chromosomal blocks, has a total size of 560 Mbp and a highly complete BUSCO score (C: 98.0%). The sampled potato aphid populations were dominated by two genotypes, one of which is absent from commercial farm settings. While the genetic and molecular basis for genotype-specific traits is unknown, the M. euphorbiae genotype distribution suggests either an intolerance to farming practices, such as insecticide use, or a broader host range in some populations. WGS data highlighted the asexual clonal lifestyle of M. euphorbiae genotypes in the UK, resolving individuals to a higher resolution than using microsatellite data. WGS data also indicates that M. euphorbiae UK populations are the result of a previous hybridization event. The work presented here will provide useful information for integrated pest management of potato aphids, elaborating on the relationship between genotype diversity and functional traits such as parasitism and insecticide resistance, and host plant use, as well as providing more resources for further comparative genomics studies within the Aphididae.

Agricultural intensification has simplified landscapes thereby reducing biodiversity, depleting natural resources, and threatening ecosystem services. Resilience to abiotic stress is therefore decreasing, creating uncertainty about effects of climate change on agricultural production and environmental degradation. While much research has focused on the direct benefits of increased plant diversity for crop productivity, there is limited evidence on how diversity and species selection affect soil stabilisation. How cover crops bind soil (rhizosheath development) has attracted little attention even though they can decrease soil erodibility. A field trial investigated the impact of cover crop diversity on rhizosheath development and soil erodibility by conducting overland flow simulations. Species (Secale cereale, Brassica juncea, Vicia faba) were chosen for their suitability to UK environmental conditions. Results established that root biomass increased with cover crop diversity and was determined by the presence of Vicia faba. Rhizosheath formation was not affected by crop diversity and was greater in treatments containing Secale cereale. Overland flow simulations showed neither rhizosheath mass nor species diversity had an impact on soil erodibility, and the field variability of soil structural and hydraulic properties had a greater influence. By providing evidence for increased plant diversity effects on agroecosystem function, this work will inform land managers about cropping practices to conserve soil function and aid in delivering environmental policy targets.

While much research has focused on the benefits of cover crop diversity for crop productivity, there is limited evidence on how root diversity and species selection stabilise soil. Although cover crops can potentially improve on-farm soil and water management, how they bind soil (through rhizosheath development) and whether multi-species cover crops offer additional benefits has attracted little attention. This study aimed to assess rhizosheath persistence in field-grown cover crops and their mixtures to understand the impact of species diversity on soil binding capacity. Brassica juncea, Secale cereale and Vicia faba were sown as monocultures and mixtures in a winter cover crop field trial near Dundee, Scotland. Soil cores were collected three times during January-March 2023. Measurements included rhizosheath mass, root length, and root hair length and density. While overall rhizosheath mass decreased by 27

Aims Root research on field-grown crops is hindered by the difficulty of estimating root biomass in soil. Root washing, the current standard method is laborious and expensive. Biochemical methods to quantify root biomass in soil, targeting species-specific DNA, have potential as a more efficient assay. We combined an efficient DNA extraction method, designed specifically to extract DNA from soil, with well-established quantitative PCR methods to estimate the root biomass of 22 wheat varieties grown in field trials over two seasons. We also developed an assay for estimating root biomass for black-grass, a common weed of wheat cultivation. Methods Two robust qPCR assays were developed to estimate the quantity of plant root DNA in soil samples, one specific to wheat and barley, and a second specific to black-grass. Results The DNA qPCR method was comparable, with high correlations, with the results of root washing from soil cores taken from winter wheat field trials. The DNA qPCR assay showed both variety and depth as significant factors in the distribution of root biomass in replicated field trials. Conclusions The results suggest that these DNA qPCR assays are a useful, high-throughput tool for investigating the genetic basis of wheat root biomass distribution in field-grown crops, and the impact of black-grass root systems on crop production.

Crop mixtures can be an important part of the toolkit for maintaining crop production while addressing the climate and nature crises. However, uncertainties around some issues may prevent their uptake. This study addressed several uncertainties, specifically the response of mixture yields to climate and management, and the impacts of mixed cropping on seed chemical composition, soil carbon and nutrients. We undertook 32 intercropping trials between 2020 and 2022 on both commercial and research farms. These varied in design, management and crop combinations, with mixture choice often determined by farmers. We assessed multiple responses including yield, weed cover, and seed and soil chemical composition. When compared to monocultures, yield gains from growing a crop mixture were roughly 20

Behavior and fitness are important ecological traits frequently measured in insect bioassays. A common method to measure them in soft-bodied herbivorous insects involves confining individuals to plant leaves using clip cages. Although studies have previously highlighted the negative effects of clip cages on leaf physiology, little is known about the impact that using this confinement method has on insect fitness. The responses of different aphid genotypes/clones to different containment methods have not previously been investigated. Here we measured key fitness traits (intrinsic rate of natural increase, mean relative growth rate, time to reach reproductive adulthood and population doubling time) in the potato aphid, Macrosiphum euphorbiae Thomas (Hemiptera: Aphididae), when confined to plants using two methods: (1) clip cages to confine aphids to individual strawberry leaves and (2) a mesh bag to confine aphids to whole strawberry plants. Our study identified a strong negative impact on all the measured aphid fitness traits when using clip cages instead of mesh bags. We also identified genotype-specific differences in response to confinement method, where clip cage confinement differentially affected the fitness of a given aphid genotype compared to the same genotype on whole plants. These results suggest that clip cage use should be carefully considered when experiments seek to quantify insect fitness and that whole plants should be used wherever possible. Given the prevalence of clip cage use in insect bioassays, our results highlight the need for caution when interpreting the existing literature as confinement method significantly impacts aphid fitness depending on their genotype.

Modern "intensive" agriculture drives the biodiversity-climate crisis but is also central to global food security. Future farming needs management approaches that maintain (or even enhance) food production while reducing negative climate and biodiversity impacts. Intercrops could provide part of the solution, increasing biodiversity and boosting production with fewer inputs. However, barriers remain to their wide-scale uptake, in particular tailoring intercrops to local equipment, management practice, and environment. We analyze data from multiple trials of cereal-legume intercrops conducted on farms across Europe between 2018 and 2021. Our study is the first attempt, to our knowledge, to quantify the yield benefits of cereal-legume intercropping undertaken at commercially relevant scales for farms across Europe. We used crop performance ratio (CPR)-the ratio of the observed intercrop yield compared to the expected yield based on monoculture yields-as our metric of intercrop performance. Using CPR, we found a roughly 30% yield gain across all sites. However, CPR was modulated by a number of factors. CPR was not strongly affected by management except for the negative effects of direct drilling and the positive effects of organic fertilizer addition. CPR also depended on intercrop composition (number and identity of components), background yields (being highest where yields were lower), and rainfall (being higher with higher rainfall). Our findings allow us to reduce uncertainty about how intercrops will perform in realistic local farm conditions, give guidance for tailoring intercrops to local farming conditions, and provide key goals for further work to integrate intercrops into sustainable farming systems.

Abstract Despite the importance of parasitoid wasps as biological control agents and the vast literature available on different aspects of their natural history and ecology, it is only recently that an interest in integrating genetics into aphid‐parasitoid studies has emerged. Some studies have been completed on the effect of genetic variation on aphid parasitism outcomes, especially after the description of aphid physiological resistance to parasitoids and its role in their co‐evolution. The interaction between aphids and parasitoids goes beyond the physiological conflict between the parasitoid egg and the aphid internal defences. A series of aphid and parasitoid attributes, that can be influenced by biotic and abiotic factors, precedes that last step in the oviposition process. The understanding of how genetic variation can play a crucial role in influencing the pre‐egg‐laying stages of the aphid‐parasitoid interaction remains relatively unexplored. Here, we review currently available information on this topic. We contextualise the aphid‐parasitoid co‐evolution process exemplified by the post‐oviposition approach. Knowledge gaps are also discussed and the significance of fulfilling them is addressed. An ecology‐evolutionary perspective on aphid‐parasitoid research is advocated, by incorporating genetic variation into the study of aphid‐parasitoid co‐evolution. This will increase the understanding of the adaptation and evolution of both organism's characteristics in response to each other and abiotic pressures, and also the implications for pest management.

Floral plantings adjacent to crops fields can recruit populations of natural enemies by providing flower nectar and non-crop prey to increase natural pest regulation. Observed variation in success rates might be due to changes in the unseen community of protective endosymbionts hosted by many herbivorous insects, which can confer resistance to various specialist natural enemies, e.g. parasitoid wasps. Reduced insect control may occur if highly protective symbiont combinations increase in frequency via selection effects, and this is expected to be stronger in lower diversity systems. We used a large-scale field trial to analyse the bacterial endosymbiont communities hosted by cereal aphids ( Sitobion avenae ) collected along transects into strip plots of barley plants managed by either conventional or integrated (including floral field margins and reduced inputs) methods. In addition, we conducted an outdoor pot experiment to analyse endosymbionts in S. avenae aphids collected on barley plants that were either grown alone or alongside one of three flowering plants, across three time points. In the field, aphids hosted up to four symbionts. The abundance of aphids and parasitoid wasps was reduced towards the middle of all fields while aphid symbiont species richness and diversity decreased into the field in conventional, but not integrated, field-strips. The proportion of aphids hosting different symbiont combinations varied across cropping systems, with distances into the fields, and were correlated with parasitoid wasp abundances. In the pot experiment, aphids hosted up to six symbionts. Flower presence increased natural enemy abundance and diversity, and decreased aphid abundance. The proportion of aphids hosting different symbiont combinations varied across the flower treatment and time, and were correlated with varying abundances of the different specialist parasitoid wasp species recruited by different flowers. Synthesis and applications . Floral plantings and flower identity can have community-wide impacts on the combinations of bacterial endosymbionts hosted by herbivorous insects. Our work highlights the potential of within-season selection for symbiont-mediated pest resistance to natural enemies with biological control impacts. This could be mitigated through increased recruitment of diverse natural enemies by incorporating functional diversity of floral resources into the environment.

Crop diversification (CD) encompasses practices such as extending crop rotation, cover cropping and intercropping practices, and growing minor crops. It has attracted increasing interest because it can produce both private benefits for farmers, including improved crop and soil health, and reduced inputs, and public goods for society, including greater biodiversity, carbon sequestration, and climate resilience. Nevertheless, CD is not widely practiced in Europe. This paper uses a conceptual framework based upon the literature on barriers to agricultural innovation and CD to guide a systematic-like literature review of existing review articles on the barriers to CD in Europe and a review of research from the European Crop Diversification Cluster, comprising six EU research projects. We compare barriers to CD uptake and identify opportunities to accelerate CD uptake, drawing four main conclusions. First, the barriers to CD are influenced by many factors: the specific crop, cropping method, geographical region, the farmer, the supply chain or market, and the institutional environment. Second, the barriers to CD uptake are interconnected and occur at multiple points along the supply chain; addressing barriers to CD uptake therefore requires a simultaneous and coordinated approach. Third, the inclusion of farmers' perspectives in the CD cluster research revealed novel barriers and solutions demonstrating that participatory and transdisciplinary agricultural research is needed to understand the on-farm reality and its influence on CD uptake. Lastly, farmers' decision-making warrants greater attention. The results highlight that farmers' decision-making is unpredictable and likely to focus on utility rather than profit maximization.

Monitoring plant responses to stress is an ongoing challenge for crop breeders, growers and agronomists. The measurement of below ground stress is particularly challenging as plants do not always show visible signs of stress in the above ground organs, particularly at early stages. Hyperspectral imaging is a technique that could be used to overcome this challenge if associations between plant spectral data and specific stresses can be determined. In this study, three genotypes of red raspberry plants grown under controlled conditions in a glasshouse were subjected to below ground biotic stresses (root pathogen Phytophthora rubi and root herbivore Otiorhynchus sulcatus ) or abiotic stress (soil water availability) and regularly imaged using hyperspectral cameras over this period. Significant differences were observed in plant biophysical traits (canopy height and leaf dry mass) and canopy reflectance spectrum between the three genotypes and the imposed stress treatments. The ratio of reflectance at 469nm and 523nm showed a significant genotype-by-treatment interaction driven by differential genotypic responses to the Phytophthora rubi treatment. This indicates that spectral imaging can be used to identify variable plant stress responses in raspberry plants.

Ecological intensification (EI) is the enhancement of ecosystem services to complement or substitute for the role of anthropogenic inputs in maintaining or increasing yields. EI has potential to increase farming's environmental sustainability, e.g. reducing environmentally harmful management activities while sustaining yields. EI is based upon ecological processes which in turn are influenced by biodiversity. We review how biodiversity, particularly vascular plant diversity, can regulate ecosystem processes relevant to EI at multiple spatial scales. At an individual plant genotype level, complementarity in functional traits has a direct impact on productivity. At in-field, population level, mixtures of crop types confer resilience to minimize the risk of pest and disease incidence and spread. Scaling up to the field level, a diversity of non-crop plants (i.e. weeds) provides resources necessary for in-field functional processes, both below ground (carbon inputs, decomposition) and above ground (resource continuity for pollinators and natural enemies). At the landscape scale, mosaics of semi-natural and managed vegetation provide buffers against extreme events through flood and drought risk mitigation, climate amelioration and pest population regulation. Overall this emphasizes the importance of heterogeneity across scales in maintaining ecosystem functions in farmland. Major research challenges highlighted by our review include the need: to better integrate plant functional diversity (from traits to habitat scales) into cropping system design; to quantify the (likely interactive) contribution of plant diversity for effective EI relative to other management options; and to optimize through targeted management the system function benefits of biodiversity for resilient, efficient and productive agroecosystems.

Aphids are important herbivorous insects that can cause significant crop damage, leading to yield reduction and economic loss. One avenue being explored to reduce aphid impacts is the development of aphid-resistant plants. Under projected climate scenarios, it is expected that plants will be exposed to greater biotic and abiotic stress, including increased herbivorous insect infestation and exposure to prolonged periods of environmental stress, particularly drought. In response to these projections, plant-aphid interactions under drought conditions have been a subject of growing interest; however, few studies have looked at the impact of drought stress on plant resistance to aphids despite the potential importance for plant breeding. Here, we examine the latest scientific advances regarding variation in plant resistance to aphids under drought, emphasizing underlying mechanisms and functional trade-offs and propose a conceptual model relating plant tolerance to drought with plant resistance to aphids.

Modern agriculture is perceived to be unsustainable having pursued a high productivity, reductionist approach for many decades. The solution proposed for restoring 'sustainability' is often encapsulated in the term 'diversity' but this is frequently as ill-defined and open to wide interpretation as the word sustainable. Key to determining whether diversity is 'the answer' is defining what diversity means in practice in the field. We attempt to describe the concepts and components of diversity and, crucially, how they might combine and interact in agricultural systems. The key concepts are: (1) complexity, (2) variation, and (3) spatio-temporal interaction, with the latter comprising (a) heterogeneity, (b) spatial connectivity, and (c) temporal connectivity. We suggest that this might lead to new strategies of diversity deployment and an index of resilience, a key ingredient of sustainability. These measures of diversity are explored in the context of crop resistance to pests and pathogens and the potential to maximise the benefits for integrated pest management in arable crops.

Purpose Silicon (Si) accumulation in plant tissues plays a vital role in alleviating biotic and abiotic stresses, including drought. Temperate regions are predicted to experience reductions in the quantity and frequency of rainfall events, potentially impacting plant Si uptake via the transpiration stream. Despite the importance for predicting plant responses to Si amendments, the effects of changes in rainfall patterns on Si uptake in cereals have not been characterised. Methods Five watering regimes were applied based on predicted precipitation scenarios, varying the quantity of water delivered (ambient, 40% or 60% reduction) and watering frequency (40% reduction in quantity, applied 50% or 25% of ambient frequency), and the effects on growth and leaf Si concentrations of a barley landrace and cultivar were determined. Results Reductions in the quantity of water reduced plant growth and yield, whereas reducing the watering frequency had little impact on growth, and in some cases partially ameliorated the negative effects of drought. Reductions in quantity of water lowered leaf Si concentrations in both the cultivar and landrace, although this effect was alleviated under the drought/deluge watering regime. The landrace had greater leaf Si concentration than the cultivar regardless of watering regime, and under ambient watering deposited Si in all cells between trichomes, whereas the cultivar exhibited gaps in Si deposition. Conclusion The impact of future reductions in rainfall on barley productivity will depend upon how the water is delivered, with drought/deluge events likely to have smaller effects on yield and on Si uptake than continuous drought.

Diversification enhances nature-based contributions to cropping system functions. ● Soil management to improve production and ecosystem function has variable outcomes. ● Management of the production-system to use legacy nutrients will reduce inputs. ● Intercrops, companion crops and cover crops improve ecological sustainability. ● Sustainable interventions within value chains are essential to future-proof agriculture. To achieve the triple challenge of food security, reversing biodiversity declines plus mitigating and adapting to climate change, there is a drive to embed ecological principles into agricultural, value-chain practices and decision-making. By diversifying cropping systems at several scales there is potential to decrease reliance on inputs, provide resilience to abiotic and biotic stress, enhance plant, microbe and animal biodiversity, and mitigate against climate change. In this review we highlight the research performed in Scotland over the past 5 years into the impact of the use of ecological principles in agriculture on sustainability, resilience and provision of ecosystem functions. We demonstrate that diversification of the system can enhance ecosystem functions. Soil and plant management interventions, including nature-based solutions, can also enhance soil quality and utilization of legacy nutrients. Additionally, this is facilitated by greater reliance on soil biological processes and trophic interactions. We highlight the example of intercropping with legumes to deliver sustainability through ecological principles and use legumes as an exemplar of the innovation. We conclude that there are many effective interventions that can be made to deliver resilient, sustainable, and diverse agroecosystems for crop and food production, and these may be applicable in any agroecosystem.