Adjacent Crops Research Articles

Pest thrips do not set field margins aside: preferred wildflowers sustain pest Frankliniella spp. (Thysanoptera: Thripidae) and their migration in commercial strawberry

Wildflowers in uncultivated field margin are important resources supporting both pest and non-pest thrips populations in agroecosystems. Environmental factors related to wildflowers have never been used as predictors to model pest thrips density in adjacent crops. Wild and cultivated flowers were sampled in strawberry field agroecosystem in Orléans Island, near Quebec City, Canada. Pest flower thrips Frankliniella intonsa and F. tritici had a wide wildflower host range, with preferences toward Leucanthemum vulgare, Trifolium pratense, Sonchus asper, and Cichorium intybus. Regression modeling revealed significant positive relationships between pest thrips density on specific wildflowers (Vicia cracca, Sinapis arvensis, S. asper, C. intybus, L. vulgare) and their density in strawberry flowers. Furthermore, thrips density within the crop decreased with distance from uncultivated field margin. Regarding crop management, knowing the associations between thrips pests and preferred wild flora as well as their spatial distribution in strawberry fields is an undeniable advantage.

Prospects for increasing the resolution of crop diversity for agroecosystem service delivery in a Dutch arable system

Finding a balance between the agroecological benefits of in-field crop diversification and the associated management demands, while maintaining expected production levels, is essential for making crop diversity work for farmers. The aim of this study was to find a workable resolution of diversity within the context of an on-station organic arable cropping systems experiment in the Netherlands. The experiment tested a gradient of crop diversity treatments from sole-crop references to strip cropping (3 m x 54 m strips sown in adjacent crop pairs of varying complexity) and pixel cropping (0.25 m2 plots each sown with one out of six total crops and arranged in 7.5 m x 12 m grids). In these treatments we assessed the performance of multiple agroecosystem service (AES) indicators (soil fertility, crop yield and quality, weed cover and diversity, and natural enemy activity density) for three focal crops (cabbage, wheat, and potato) using three years of field data and a three-part analysis. First, we used linear mixed models to assess the effects of each diversification treatment on the AES indicators. We found no clear indication that one treatment performed better than the rest across AES indicators. Second, we developed a novel method for quantifying the temporal, spatial, and genetic structural diversity of the tested treatments into compound diversity scores, and used these scores to analyze response relationships between increasing in-field diversity and AES delivery. Here we found that increasing compound diversity had a positive effect on the indicators weed species diversity and natural enemy activity density. For production indicators, we observed an inflection point between the most diverse strip cropping treatment and the pixel cropping treatment, with pixel cropping performing notably poorly. Third, we used a multivariate analysis approach to assess the contribution of temporal, spatial, and genetic diversity to AES delivery, but found no clear effects of individual diversity dimensions on AES delivery. These findings suggest that prospects for strip cropping are better than for pixel cropping when it comes to balancing production aims with increases in other AES while also maintaining management feasibility. Reconciling management shortcomings in highly diverse cropping systems (e.g. through the development of appropriate technologies) may be one way to mitigate trade-offs between ecological and production aims at resolutions of diversity higher than strip cropping.

Insights of smallholder farmers on the trade-offs of eucalyptus plantation

Eucalyptus is a popular evergreen perennial tree that grows quickly. Due to its diverse economic value and wide range of adaptations, the eucalyptus is commonly grown in tropical and subtropical regions. Eucalyptus is an economically important tree. However, the economic importance of eucalyptus ensued at the expense of undesirable ecological consequences. This qualitative study reports the advantages and disadvantages of eucalyptus woodlot establishment on the productivity of arable and grazing lands. In this study, nine knowledgeable farmers were involved in an in-depth individual interview and four focus group discussions were conducted. Farmers have frequently reported the negative impact of eucalyptus plantations on the productivity of the agricultural system. Eucalyptus serves as a refuge for crop pests and pathogens such as aphids and rust. Besides, the shade suppresses the development of the understory and adjacent crops, pastures, fodder, and other species of native trees and shrubs if they are planted together. Eucalyptus has increasingly replaced eco-friendly native trees and shrubs traditionally used as hedges, windbreaks, fodder, shelters for domestic and wild animals, and enhancers of soil fertility. Besides deteriorating soil fertility, structure, and moisture, it drains wetlands, springs, and streams and reduces the flow of rivers. Nevertheless, farmers acknowledged the importance of eucalyptus as a construction material, a source of fuelwood and charcoal, and income. To make the best use of eucalyptus woodlots without imposing adverse effects on agroecology, farmers have suggested that plantation sites should be marginally suitable for crop and livestock production. The expanded plantation needs to be contracted by removing a significant proportion of the established eucalyptus woodlots. Plantations of eucalyptus around watering points should be discouraged. Fast-growing, resilient, and eco-friendly tree species, such as those from Grevillea and Populus species, and sibling (leguminous) trees and shrubs delivering comparable products and services should be sought after to replace the significant proportion of the established eucalyptus woodlot.

Hedgerows on Crop Field Edges Increase Soil Carbon to a Depth of 1 meter

Effective incentivization of soil carbon (C) storage as a climate mitigation strategy necessitates an improved understanding of management impacts on working farms. Using a regional survey on intensively managed farms, soil organic carbon (SOC) concentrations and stocks (0–100 cm) were evaluated in a pairwise comparison of long-term (10+ years) woody hedgerow plantings and adjacent crop fields in Yolo County, CA, USA. Twenty-one paired sites were selected to represent four soil types (Yolo silt loam, Brentwood clay loam, Capay silty clay, and Corning loam), with textures ranging from 16% to 51% clay. Soil C was higher in the upper 100 cm under hedgerows (14.4 kg m−2) relative to cultivated fields (10.6 kg m−2) and at all depths (0–10, 10–20, 20–50, 50–75, and 75–100 cm). The difference in SOC (3.8 kg m−2) did not vary by soil type, suggesting a broad potential for hedgerows to increase SOC stocks. Assuming adoption rates of 50 to 80% across California for hypothetical field edges of average-size farms, and an identical SOC sequestration potential across soil types, hedgerows could sequester 10.8 to 17.3 MMT CO2e, or 7 to 12% of California’s annual greenhouse gas reduction goals.

Absorption and translocation of [14C]2,4-dichlorophenoxyacetic acid in herbicide-tolerant chromosome substitution lines of Gossypium hirsutum L

Upland cotton is sensitive to 2,4-dichlorophenoxyacetic acid (2,4-D), and spray drift from adjacent crops can cause yield loss. The identification of potentially 2,4-D-tolerant cotton chromosome substitution (CS) lines with well-characterized tolerance mechanisms could provide a significant step into the development and genetic improvement of upland cotton. Experiments were conducted to understand the possible mechanism of herbicide tolerance in CS-T04-15, CS-T07, and CS-B15sh, 2,4-D herbicide-tolerant cotton CS lines compared with TM-1, the 2,4-D herbicide-susceptible recurrent parent of the CS line. Using [ 14 C]2,4-D, the percent absorption rate and the translocation patterns of the 14 C-labeled herbicide at 6 to 48 h after treatment (HAT) were determined. The tolerant cotton CS lines showed 15%–19% [ 14 C]2,4-D uptake, while TM-1 exhibited a reduced uptake of only 1.4% [ 14 C]2,4-D at 24 HAT. Distribution of the absorbed [ 14 C]2,4-D showed that 2%–5% was translocated outside the treated leaf in the tolerant CS lines. In contrast, 77% of the herbicide was translocated above and below the treated leaf in line TM-1. Interestingly, CS-T04-15 showed a restricted movement of 14 C below the treated leaf at 6 to 48 HAT, suggesting novel information on the mechanisms of herbicide tolerance to 2,4-D in cotton. This finding is the first report on upland cotton demonstrating a complex differential uptake and translocation associated with herbicide tolerance for [ 14 C]2,4-D in cotton CS lines.

In‐field cover crop strips support carabid communities and shape the ecological trait repartition in maize fields

Abstract The enhancement of pest regulation service in crops depends for a large part on the capacity of agroecological practices to increase the presence of key species or functional traits in arthropod communities within fields. We investigated the effects of undestroyed strips of winter cover crops in maize fields on carabid community composition, and on the distribution of three ecological traits: diet, wing status and body size. We found that the community composition and the distribution of ecological traits in the in‐field cover crop strips had commonalities with both adjacent cropped areas and field margins. Some species were recorded mostly or only in the strips indicating that strips could support carabid species and help increase local diversity from the first year of establishment. The activity‐density of Poecilus cupreus and Pterostichus melanarius was higher in the cropped proximity of the strip, and the body size was influenced by the distance from the strip. Our results suggest that carabid communities are shaped by the habitat type, but the influence of such agroecological infrastructures on communities of adjacent crops is minor beyond a distance of 10 m. However, overall species abundance was increased and thus potentially provided enhanced pest regulation.

Hedgerows increase the diversity and modify the composition of arbuscular mycorrhizal fungi in Mediterranean agricultural landscapes

Sustainable agriculture is essential to address global challenges such as climate change and biodiversity loss. Hedgerows enhance aboveground biodiversity and provide ecosystem services, but little is known about their impact on soil biota. Arbuscular mycorrhizal (AM) fungi are one of the key components of belowground biodiversity. We compared the diversity and composition of AM fungal communities at four farmland sites located in Central Spain, where 132 soil samples in total were collected to assess soil physical and chemical properties and the AM fungal communities. We compared the richness (number of AM fungal taxa), taxonomic, functional, and phylogenetic diversity, and structure of the AM fungal communities across three farmland habitat types, namely hedgerows, woody crops (olive groves and vineyard), and herbaceous crops (barley, sunflower, and wheat). Our results showed positive effects of hedgerows on most diversity metrics. Almost 60% of the AM fungal taxa were shared among the three farmland habitat types. Hedgerows increased AM fungal taxonomic richness (31%) and alpha diversity (25%), and especially so compared to herbaceous crops (45% and 28%, respectively). Hedgerows harbored elevated proportions of AM fungi with non-ruderal life-history strategies. AM fungal communities were more similar between hedgerows and woody crops than between hedgerows and adjacent herbaceous crops, possibly because of differences in tillage and fertilization. Unexpectedly, hedgerows reduced phylogenetic diversity, which might be related to more selective associations of AM fungi with woody plants than with herbaceous crops. Overall, the results suggest that planting hedgerows contributes to maintain belowground diversity. Thus, European farmers should plant more hedgerows to attain the goals of the EU Biodiversity Strategy for 2030.

Insecticidal Management of Rangeland Grasshoppers Using a Remotely Piloted Aerial Application System

Grasshoppers are integral parts of rangeland ecosystems but also have the potential to reach population densities high enough (outbreaks) to cause serious economic damage from forage loss and affect adjacent crops. The objective of this study was to investigate the efficacy of treating grasshopper population hotspots with a liquid insecticide using a remotely piloted aerial application system (RPAAS), as opposed to fixed-wing aircraft, which is the most common method currently in use. A liquid insecticide, Sevin XLR PLUS (containing carbaryl), was applied on replicated 4.05-hectare (10-acre) plots with an RPAAS on a ranch in New Mexico. Our results demonstrated that Sevin XLR PLUS significantly suppressed grasshopper populations over a 14-day period (normalized population reduction was 79.11 ± 8.35% SEM) and quite rapidly (mostly by day 3) compared to untreated controls. These results are comparable to those achieved with fixed-wing aircraft. The RPAAS covered the whole test area in a single flight in approximately 5 min, making these population hotspot treatment applications relatively rapid, potentially more cost-effective, and more targeted in comparison to fixed-wing aircraft. Before adoption as an application method option, further research is recommended on using an RPAAS to cover larger areas in combination with using diflubenzuron-based insecticides, which are often preferred.

Soil Quality Enhancement with Orchard Age in Pecan Orchards of the Southeastern U.S. Coastal Plain

Pecan (Carya illinoinensis) orchards in Georgia and throughout the southeastern United States are commonly established from land that had previously been used for row cropping systems. Soil quality is characteristically low in the loamy-sand, low pH soils of the southeastern Coastal Plain. Changes in land use are known to exhibit different effects on soil quality; however, no studies specifically address soil enhancement from converting row crop land to pecan orchards in this region. Sampling was conducted in eight counties throughout the coastal plain of South Georgia in 2020 and 2021. The objectives of this study were to analyze and compare soil quality indicators of pecan orchards of varying ages and adjacent row crop fields. Soil quality indicators analyzed include soil organic matter (SOM), active carbon or permanganate oxidizable carbon (POXC), aggregate stability, cation exchange capacity (CEC), bulk density, porosity, Solvita CO2-Burst, SLAN (Solvita labile-amino nitrogen), pH, and total N. Results from this study demonstrate that pecan orchards under commercial management had higher soil quality compared with row crop fields based on the indicators measured. Active carbon and Solvita CO2-Burst measurements suggest that pecan orchards exhibited significantly higher rates of microbial activity and soil respiration. Indicators of soil microbial activity such as active carbon and Solvita CO2-Burst were strongly correlated with SOM, which explained much of the variation observed in these measurements of soil microbial activity. Selected soil quality indicators also provide evidence that the soil quality of commercial pecan orchards in this region improves with orchard age.

Disentangling arthropod and plant resources consumed by Orius spp. in peach and alfalfa crops by metagenomic analysis

Agricultural intensification is affecting the biological control of insect pests, an important component for sustainable crop production. To understand the changing patterns of insect abundance within an agroecosystem, it is necessary to disentangle the trophic interactions between species, and metabarcoding is an excellent alternative to show them. In the Ebro Basin (NE Iberian Peninsula), agricultural landscapes are composed of a mosaic of crops scattered with natural and semi-natural habitats, where the presence of Orius spp., used as biocontrol agents, is well known. To shed light on their predatory role in this area, a previously developed metabarcoding multi-primer method has been used to study the arthropod and plant most frequently resources consumed by some field-collected Orius, sampled at different dates in a peach and an alfalfa adjacent crop. Their high-throughput sequencing (HTS) analysis showed the consumption of 15 arthropod and 12 plant taxa. Eight of them were consumed by O. laevigatus, six by O. majusculus and 23 by O. niger. The obtained results showed that HTS is a powerful tool in studies of trophic interactions in agroecosystems. Among the detected arthropods, other natural enemies were present, showing a certain degree of intraguild predation, which has been demonstrated by developing a new added strategy in the bioinformatic analysis. Detected plant consumption indicates that Orius forages on several plant species, showing their movement from them to the sampled crops. These plants could have a potential role in attracting or maintaining these predators in both crops in biological control strategies.

Application of UAV Remote Sensing in Monitoring Water Use Efficiency and Biomass of Cotton Plants Adjacent to Shelterbelt.

Tree shelterbelts are crucial for maintaining the ecological environment of oasis, but they may also compete for soil water with adjacent crops, affecting crop yields. To evaluate the impacts of the shelterbelt on water use efficiency (WUE) and normalized water productivity (WP) of adjacent cotton plants, the biomass (B) and WUE of cotton with different distances from the shelterbelt (0.1H, 0.5H, 1H, 2H, and 3H; average tree height = 15 m [H]) were estimated based on unmanned aerial vehicle (UAV) remote sensing data combined with the FAO crop water response model AquaCrop. Besides, the accuracy and universality of the estimation method were also evaluated. The results showed that the method based on UAV remote sensing data and AquaCrop can accurately estimate the impact range and intensity of shelterbelt on WUE, water consumption, and B of adjacent cotton plants. Fierce water competition between shelterbelt and cotton was detected within 0.1H−1H, and the competitiveness of the shelterbelt was weaker in the plots >1H than in the 0.1H−1H. The B, actual evapotranspiration (Tc), and WUE of cotton at 0.1H decreased by 59.3, 48.8, and 23.6%, respectively, compared with those at 3H, but the cotton plants at 2H and 3H were completely unaffected by the shelterbelt. Besides, the B estimated based on WP (root mean square error [RMSE] = 108 g/m2, d = 0.89) was more accurate than that estimated based on WUE (RMSE = 118 g/m2, d = 0.85). This study clarifies the inter-species competition for soil water between crops and shelterbelts under drip irrigation in oases in China.

Using spatially-explicit plant competition models to optimise crop productivity in intercropped systems

Intercropping, by capitalizing on positive biodiversity–productivity relationships, represents a promising option to increase agricultural sustainability. However, the complexity and context-dependency of plant–plant interactions can make it challenging for farmers to find suitable crop combinations. Furthermore, intercropping is usually implemented with standard inter-row spacing and plant densities based on monoculture practices, which might not be the ideal configuration to maximize yield.Here we present a spatially-explicit yield analysis method based on plant ecological interaction models that allowed to optimize crop species combinations and spatial configurations for maximal yield in intercropped systems. We tested this method with three crop species, namely oat, lupine, and camelina. In a first step, field experiments in which crop density and adjacent crop type were varied provided us with indications on which species would compete more with each other. The results showed us that oat and camelina strongly competed with each other. In addition, the distance experiments allowed us to understand how the changes in yield associated with the presence of neighbors vary with distance. This allowed us to find the sets of parameters (identity of neighbors, sowing density, distances between individuals) that optimise intercrop yield (measured as Land Equivalent Ratio [LER]) for the three considered species. Specifically, we show that alternating rows of species led to higher LERs than a homogeneous species mixing, and that 3-species combinations are not necessarily more performant than the best 2-species combinations. In addition, we show that increasing the density of oat is generally beneficial for LER, while increasing the density of lupine is not.By modelling crop yield from simple and reproducible density and distance experiments, our results allow to optimize crop mixtures in terms of species combinations and spatial configurations, for maximal crop yield.

Tomato (Solanum lycopersicum) specialized pollination is isolated from neighboring plants and pollinators

Tomato is one of the crops that require buzz pollination, for which a pollinator vibrates the tubular anthers for pollen to be released. This process is efficiently carried out by wild bees, whose distribution varies according to the geographical location and the particular characteristics of the different agroecosystems. The pollination network associated with tomato fields located in an agricultural area of ​​ Cuba was determined by field observations. In addition, it was studied whether pollination influences tomato yield, through exclusion experiments and comparing the characteristics of the fruits obtained in the presence or absence of pollinators. The pollination network consisted of 241 interactions between 12 plants, including tomato, adjacent crops such as papaya and pumpkin, and ruderal species, and 11 floral visitors, fundamentally bees, with 5 species involved. Tomato flowers were almost exclusively visited by the bee species Exomalopsis pulchella, capable of buzz pollination. Species of the genus Exomalopsis are frequent pollinators of tomato in the Neotropic. This denotes a temporary specialization in the use of tomato´s floral resources by Exomalopsis pulchella. Apis mellifera was not detected visiting tomato flowers, despite being present in the pollination network associated with the studied agroecosystem. Pollination significantly increased the dimensions of tomato fruits. Exomalopsis pulchella also visited the ruderal plants Asteraceae sp., Commelinaceae sp. and Milleria quinqueflora. This should be taken into account in the management of the ruderal plant communities that surround the tomato fields, in order to promote and guarantee the presence of the main pollinator of this crop.

Adjacent crop type impacts potential pollinator communities and their pollination services in remnants of natural vegetation

AbstractAimPollination plays a crucial role in the conservation of many plant species persisting in fragmented, human‐dominated landscapes. Pollinators are known to be instrumental in maintaining genetic diversity and metapopulation dynamics for many plant species and are important for providing ecological services that are essential in agricultural landscapes where populations of native plants are highly isolated. Numerous studies have explored the value of remnant native vegetation for supporting pollination services to crop species, yet the effect of mass‐flowering crops on the pollinator communities and the pollination services they provide to native plant communities persisting in fragmented landscapes are less well understood. Here, we assess the influence of the presence and phenology of a mass‐flowering crop to pollinator community structure, abundance, and pollen load composition in remnant vegetation in complex agricultural landscapes.LocationSouth‐west Western Australia, Australia.MethodsWe recorded the composition and abundance of insect flower visitors and their pollen loads in isolated remnants of York Gum‐Jam woodlands adjacent to canola (insect‐attracting) or wheat (non‐insect‐attracting) fields over two years.ResultsAll bees were much more sensitive to adjacent crop type (neighbouring canola or wheat) than non‐bee pollinators. Honeybees were the most abundant pollinators in canola fields during peak flowering. Honeybee abundance increased in canola‐adjacent reserves post canola bloom, potentially indicating a movement into reserves as crop flowering waned. Native bees were the most diverse in remnant vegetation. Pollen loads of native bees were more mixed (increased pollen richness and evenness) when sampled next to canola fields compared to wheat fields.Main conclusionThe availability of potential insect pollinators to remnant wildflower communities in agricultural landscapes is context dependent. Whether sampled communities were adjacent to wheat or canola in a landscape significantly impacted the abundance of potential pollinators in certain landscape elements, but not others, and the composition of pollen loads carried by these insects. Results offer novel insights about the influence of landscape context on pollinator communities and the potential pollination services available for the conservation of native plant species in highly fragmented agricultural landscapes.

Perennial Flowering Plants Sustain Natural Enemy Populations in Gobi Desert Oases of Southern Xinjiang, China.

Simple SummaryNatural habitats are essential providers of biological conservation services. The crucial role of the Gobi Desert, a dominant landscape of desert-oasis ecosystems in natural predator conservation is poorly understood, especially in southern Xinjiang, China’s Tarim Basin, where the Gobi Desert is directly adjacent to farmland and characterized by extremely sparse vegetation and more severe climatic conditions. In this context, we investigated the floral composition of the Gobi Desert and gauged the identity, relative abundance, and temporal dynamics of predatory insects associated with the prevailing plant species. We also explored whether certain plant traits and herbivore abundance are related to either natural enemy identity or relative abundance. Our results demonstrate that perennial flowering plants, such as Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae), are the dominant species of vegetation community in the Gobi Desert, and could sustain diversified arthropod predators, i.e., ladybeetles, spiders, and other natural enemies. This work not only informs sustainable pest management initiatives, but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.Natural habitats play crucial roles in biodiversity conservation and shape the delivery of ecosystem services in farming landscapes. By providing diverse resources to foraging natural enemies, they can equally enhance biological pest control. In this study, we described the plant community and foliage-dwelling invertebrate predators within non-crop habitats of the Gobi Desert oases in southern Xinjiang, China. We assessed whether plant-related variables (i.e., species identity, flowering status) and herbivore abundance affect natural enemy identity and abundance. A total of 18 plant species belonging to 18 genera and 10 families were commonly encountered, with Apocynum pictum (Apocynaceae), Phragmites communis (Poaceae), Karelinia caspia (Asteraceae), and Tamarix ramosissima (Tamaricaceae) as the dominant species. Certain plant species (P. communis) primarily provide shelter, while others offer (floral, non-floral) food resources or alternative prey. Predatory ladybeetles and spiders were routinely associated with these plants and foraged extensively within adjacent field crops. Plant traits and herbivore abundance explained up to 44% (3%–44%) variation in natural enemy community and exhibited consistent, year-round effects. Among all plant species, A. pictum consistently had a significantly higher abundance of resident natural enemies, except for August 2019. Our study underlines how perennial flowering plants, such as A. pictum, are essential to sustain natural enemy communities and related ecosystem services in arid settings. This work not only informs sustainable pest management initiatives but also shows how non-crop habitats at the periphery of agricultural fields underpin ecological resilience under adverse climatic conditions.

Pesticide Regime Can Negate the Positive Influence of Native Vegetation Donor Habitat on Natural Enemy Abundance in Adjacent Crop Fields

The benefits of non-crop vegetation to conservation biological control of insect pests in adjacent crops have often been demonstrated. Other studies have established that pesticide use can negatively impact natural enemies; but little is known about the outcomes from providing non-crop vegetation in systems with pesticide use. Here we conducted a natural experiment, sampling arthropods from within a set of four fields with varying pesticide use intensities that were otherwise similar and had perennial native vegetation adjacent to a single edge. Bayesian network analysis was applied to model the entire data set, then sensitivity analysis of numbers of arthropods captured in pitfall traps and sticky traps revealed that the overall effect of pesticide toxicity was large. Numbers of multiple arthropod taxa were especially strongly reduced in fields with pesticide regimes that had greater calculated toxicity scores. The effects on natural enemy numbers of the presence of adjacent perennial native vegetation was weaker than the effect of pesticide regime for all taxa except for Staphilinidae, for which it was equivalent. The benefit to in-crop numbers of natural enemies from the adjacent vegetation was strongest for ground active Araneae, Formicidae, and Dermaptera. Descriptive statistical analysis of the spatial distribution in the least heavily sprayed field suggested that the native vegetation was donor habitat for in-crop natural enemies, especially Hymenoptera, Dermaptera, and Formicidae, with numbers elevated close to the native vegetation, an effect that was apparent for around 100 m. Conservation of invertebrates in agricultural landscapes, including efforts to promote natural enemies for conservation biological control, are strongly impeded by “real world” pesticide regimes that include frequent applications and toxic compounds. Landscape features such as perennial native woody vegetation are potentially important refuges for a wide range of natural enemy taxa. The donor habitat effect of such refuges can elevate in-crop densities of these important ecosystem service providers over a scale of around 100 m, implying scope to enhance the strength of biological control in large fields (around 4 ha) by use of entirely wooded margins provided pesticide use is moderated.

Effects of hedgerows on the preservation of spontaneous biodiversity and the promotion of biotic regulation services in agriculture: towards a more constructive relationships between agriculture and biodiversity

ABSTRACT Central to the agroecological transition is biodiversity, which, once restored in agroecosystems, should provide multiple ecosystem services that result from the interactions between different organisms. However, the diversity of expected services raises questions about the capacity of agroecosystems to simultaneously provide many of them as well as the possible existence of synergies and antagonisms. In particular, the relationships between crop-associated biodiversity (i.e. biodiversity in action in crops) and spontaneous biodiversity (i.e. biodiversity not directly related to agriculture) remain unclear. In this article, we analyse the impact of hedgerows on the preservation of spontaneous biodiversity, on the promotion of biotic regulation services such as pollination and pest control in agriculture, and on the interactions between spontaneous and associated biodiversity. Our analysis of the scientific literature shows that hedgerows are unique assets for the preservation of spontaneous biodiversity, while they also provide biotic regulation services to adjacent crops but only under specific conditions, which need to be better understood. We propose a functional conceptual framework of the ecological effects of hedgerows on associated biodiversity and we highlight the possible synergistic and antagonistic effects related to hedgerow characteristics and the life-history traits of the organisms under consideration. Our analysis therefore seeks to overcome the cleavage between associated biodiversity and spontaneous biodiversity. This approach is in keeping with a more harmonious relationship between agriculture and biodiversity.

Pesticide exposure of wild bees and honey bees foraging from field border flowers in intensively managed agriculture areas

Bees are critical for food crop pollination, yet their populations are declining as agricultural practices intensify. Pollinator-attractive field border plantings (e.g. hedgerows and forb strips) can increase bee diversity and abundance in agricultural areas; however, recent studies suggest these plants may contain pesticides. Pesticide exposure for wild bees remains largely unknown; however, this information is needed to inform agricultural practices and pesticide regulations meant to protect bees. It is important to determine whether border plantings that attract and support pollinators may also deliver pesticides to them. In this study, we collected various samples for pesticide residue analysis, including: multiple species of wild bees, honey bees, flowers from four types of bee-attractive field border plants, and soil. Silicone bands were also utilized as passive aerial samplers of pesticide residues. The five pesticides detected most frequently across all samples were the insecticide bifenthrin, the herbicides thiobencarb, metolaclor, and propanil, and the fungicide fluopyram. We detected the greatest number of parent pesticides in bands (24), followed by soil (21). Pesticides were also detected in field border plant flowers (16), which do not receive direct pesticide applications, and included many products which were not applied to adjacent field crops. Pesticide concentrations were lower in bees than in flowers but higher in bees than in soils. Pesticide residue per bee (ng/bee) increased with increasing wild bee size, though pesticide concentration (ng/g) did not increase. While honey bees and wild bees contained a similar number and concentration of pesticides overall, pesticide mixtures varied by bee type, and included some mixtures known to cause sublethal effects. The results from this study highlight the benefits of measuring more sample types to capture the total exposome of bees, including a greater range of bee species, as well as the need to consider exposure to pesticides at the landscape level.

Native Flowering Border Crops Attract High Pollinator Abundance and Diversity, Providing Growers the Opportunity to Enhance Pollination Services.

Over the past century, habitat loss from agricultural intensification has contributed to pollinator decline. One way to mitigate the harmful effects of agricultural intensification is through the re-introduction of native flowering plants as border strips that provide supplemental floral and nesting resources to pollinators. However, border crop species vary in bloom period and flower densities, and are thus likely to attract different suites of pollinator species. Resulting differences in pollinator community composition are likely to affect their ability to provide pollination services to adjacent crop habitat. To address these issues, we implemented a two-year study on the impact of different flowering border crops on pollinator abundance, richness, and community composition. We also examined which crop features (bloom duration, number of flowers, floral area) were most likely to affect pollinator densities. We found that native flowering plant border crops of diverse prairie mix and monocultures of silflower (Silphium integrifolium Michx.) and cup plant (Silphium perfoliatum L.) attracted the highest abundance and species richness of bees and pollinator groups combined, while alfalfa (Medicago sativa L.) attracted the highest lepidopteran abundance and species richness. We also found a significant, positive relationship between pollinator abundance and floral resource amount and bloom duration. These findings offer valuable insight into the impacts of different land management strategies on different pollinator groups, and thus provide landowners with management options for attracting specific pollinator groups and species.

High flower richness and abundance decrease pollen transfer on individual plants in road verges but increase it in adjacent fields in intensively managed agroecosystems

Road verges can facilitate the movement of pollinators and pollen in intensively managed agroecosystems, reducing the negative impacts of fragmentation (i.e., isolation of wild pollinator communities) and enhancing the pollination service provided to wild plants. To assess the role of road verges in sustaining the pollination service to wild plants, we studied gardens consisting of two plant species arranged within sixteen road verges and their adjacent fields during two consecutive seasons in the Argentine Pampas. We assessed the influence of attributes of road verges on pollination service at different scales: road verges width, species richness of flowering plant, and flower abundance (patch scale), crops and successional pastures (adjacent land use scale), and landscape heterogeneity (landscape scale). We measured the pollination service provided to two species of potted plants (Hirschfeldia incana and Lobularia maritima) in three different ways: visitation rate, conspecific and heterospecific pollen transfer to stigmas, and distance of pollen transfer from a fixed source. The number of conspecific and heterospecific pollen grains deposited on stigmas decreased with an increased abundance of floral units in associated road verges, which is caused by a dilution effect on individual plant pollination. Also, the pollen transfer into adjacent fields decreased with an increased abundance of floral units in the nearby road verges, which is caused by a decrease of pollen spillover into adjacent crop fields. The visitation rate within adjacent fields increased with higher flowering plant species richness in associated road verges. Also, the number of conspecific pollen grains in the road verges adjacent to successional pastures increased with higher flowering plant species richness in road verges, which results in a concentration effect of pollinator visits and pollen transfer into road verges. We conclude that managing flower abundance and increasing flowering plant species richness in road verges are crucial practices for maintaining the pollination service of entomophilous plants in intensively managed agroecosystems.