187 research outputs found
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Integrated crop pollination to buffer spatial and temporal variability in pollinator activity
Insect pollination improves the yield and quality of many crops, yet there is increasing evidence of insufficient insect pollinators limiting crop production. Effective Integrated Crop Pollination (ICP) involves adaptable, targeted and cost effective management of crop pollination and encourages the use of both wild and managed pollinators where appropriate. In this study we investigate how the
addition of honeybee hives affects the community of insects visiting oilseed rape, and if hive number and location affect pollinator foraging and oilseed rape pollination in order to provide evidence for effective ICP. We found that introducing hives increased overall flower visitor numbers and altered the pollinator community, which became dominated by honeybees. Furthermore a greater number of
hives did not increase bee numbers significantly but did result in honeybees foraging further into fields. The timing of surveys and proximity to the field edge influenced different pollinators in different ways and represents an example of spatial and temporal complementarity. For example dipteran flower visitor numbers declined away from the field edge whereas honeybees peaked at intermediate distances into the field. Furthermore, no significant effects of survey round on wild bees overall was observed but honeybee numbers were relatively lower during peak flowering and dipteran abundance was greater in later survey rounds. Thus combining diverse wild pollinators and managed species for
crop pollination buffers spatial and temporal variation in flower visitation. However we found no effect of insect pollination on seed set or yield of oilseed rape in our trial, highlighting the critical need to understand crop demand for insect pollination before investments are made in managing pollination services
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Economic valuation of natural pest control of the summer grain aphid in wheat in South East England
Wheat (Triticum spp.) is the most important arable crop grown in the UK, and the grain aphid (Sitobion avenae) is one of the key pests of this crop. Natural enemies could help suppress grain aphid and reduce unnecessary insecticide inputs, but few studies have estimated the economic value of natural pest control in this crop-pest system, which could help inform effective integrated pest management strategies. Based on a natural enemy exclusion experiment carried out in South East England, this study used an economic surplus model to estimate the value of predators and parasitoids to control summer grain aphid in wheat in this region. Incorporating three levels of spray intensity and three levels of pest infestation, the annual economic value of natural pest control service was conservatively estimated to be £0-2.3 Million. Under the medium pest infestation level, a 10% increase in the proportion of wheat fields using economic threshold-based spray method would increase this value by 23% (£0.4 Million). 71% of the value would benefit wheat growers. A potential rise in insecticide costs due to resistance development would also enhance the value of natural pest control. These findings support growing efforts from policy-makers to promote this ecosystem service in agriculture
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The benefits of hedgerows for pollinators and natural enemies depends on hedge quality and landscape context
Ecological intensification advocates the harnessing of regulating and supporting ecosystem services to promote more sustainable food production, and this relies on effective management of non-cropped habitats. Hedgerows are an important component of the landscape in many farming systems across the world, management of which provides a potential mechanism to enhance ecological intensification. Here we investigate the value of hedgerows in Southern England as a source of functionally important taxa, and how hedgerow quality and local landscape composition impact on their potential contribution to sustainable agriculture in arable landscapes. We show that hedgerows are a source habitat for many natural enemies which spill over into neighbouring fields, and that hedgerows provide a valuable forage resource and corridor for movement of pollinators. Hedgerow quality affects these benefits and continuous unbroken hedgerows, with a high diversity of woody species, are more valuable for the provision of bumblebees and Linyphiid spiders, while the presence of trees within the hedgerow supports Lycosid spiders. Floral resources, beyond the woody hedgerow species themselves, are also a key forage resource for hoverflies. The impact of these hedgerows on invertebrate abundance is moderated by local landscape, and hedgerows are a more valuable forage resource for pollinators in more intensely managed landscapes. Our study shows that in order to support abundant and a broad range of natural enemies and pollinators in agricultural landscapes, both hedgerows and local semi-natural habitats need to be protected and managed. The benefit of hedgerows, as a habitat for functionally important taxa depends on hedgerow quality and management practices such as avoiding gaps, high hedge species diversity and maintaining an abundant understory of plants, can improve their value for ecological intensification
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Insect pollination as an agronomic input: strategies for oilseed rape production
1.Ecological intensification involves the incorporation of biodiversity based ecosystem service management into farming systems in order to make crop production more sustainable and reduce reliance on anthropogenic inputs, including fertiliser and insecticides.
2.The benefits of effectively managing ecosystem services such as pollination and pest regulation for improved yields have been demonstrated in a number of studies, however recent evidence indicates that these benefits interact with conventional agronomic inputs such as fertiliser and irrigation. Despite the important contribution of biodiversity‐based ecosystem services to crop production their management is rarely considered in combination with more conventional agronomic inputs.
3.This study combines a number of complementary approaches to evaluate the impact of insect pollination on yield parameters of Brassica napus and how this interacts with a key agronomic input, fertiliser. We incorporate data from a flight cage trial and multiple field studies to quantify the relationships between yield parameters to determine whether insufficient insect pollination may limit crop yield.
4.We demonstrate that, by producing larger seeds and more pods, B. napus has the capacity to modulate investment across yield parameters and buffer sub‐optimal inputs of fertiliser or pollination. However, only when fertiliser is not limiting can the crop benefit from insect pollination, with yield increases due to insect pollination only seen under high fertiliser application.
5.A non‐linear relationship between seed set per pod and yield per plant was found, with increases in seed set between 15 and 25 seeds per pod resulting in a consistent increase in crop yield. The capacity for the crop to compensate for lower seed set due to sub‐optimal pollination is therefore limited.
6.Synthesis and applications. Oilseed rape has the capacity to compensate for sub‐optimal agronomic or ecosystem service inputs although this has limitations. Insect pollination can increase seed set and so there are production benefits to be gained through effective management of wild pollinators or by utilising managed species. Our study demonstrates however that increased insect pollination cannot simply replace other inputs, and if resources such as fertiliser are limiting, then yield potential cannot be reached. We highlight the need to consider insect pollination as an agronomic input to be effectively managed in agricultural systems
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Policies for ecological intensification of crop production
Ecological intensification aims to increase crop productivity by enhancing biodiversity and associated ecosystem services, while minimizing the use of synthetic inputs and cropland expansion. Policies to promote ecological intensification have emerged in different countries, but they are still scarce and vary widely across regions. Here, we propose ten policy targets that governments can follow for ecological intensification
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The identity of crop pollinators helps target conservation for improved ecosystem services
Insect pollinated mass flowering crops are becoming more widespread and there is a need to understand which insects are primarily responsible for the pollination of these crops so conservation measures can be appropriately targeted in the face of pollinator declines. This study used field surveys in conjunction with cage manipulations to identify the relative contributions of different pollinator taxa to the pollination of two widespread flowering crops, field beans and oilseed rape. Flower visiting pollinator communities observed in the field were distinct for each crop; while field beans were visited primarily by a few bumblebee species, multiple pollinator taxa visited oilseed, and the composition of this pollinator community was highly variable spatially and temporally. Neither pollinator community, however, appears to be meeting the demands of crops in our study regions. Cage manipulations showed that multiple taxa can effectively pollinate both oilseed and field beans, but bumblebees are particularly effective bean pollinators. Combining field observations and cage manipulations demonstrated that the pollination demands of these two mass flowering crops are highly contrasting, one would benefit from management to increase the abundance of some key taxa, whilst for the other, boosting overall pollinator abundance and diversity would be more appropriate. Our findings highlight the need for crop specific mitigation strategies that are targeted at conserving specific pollinator taxa (or group of taxa) that are both active and capable of crop pollination in order to reduce pollination deficits and meet the demands of future crop production
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A whole ecosystem approach to pear psyllid (Cacopsylla pyri) management in a changing climate
Whole ecosystem-based approaches are becoming increasingly common in pest management within agricultural systems. These strategies consider all trophic levels and abiotic processes within an ecosystem, including interactions between different factors. This review outlines a whole ecosystem approach to the integrated pest management (IPM) of pear psyllid (Cacopsylla pyri Linnaeus) within pear (Pyrus communis L.) orchards, focusing on potential disruptions as a result of climate change. Pear psyllid is estimated to cost the UK pear industry £5 million per annum and has a significant economic impact on pear production globally. Pesticide resistance is well documented in psyllids, leading many growers to rely on biological control using natural enemies during the summer months. In addition, multiple insecticides commonly used in pear psyllid control have been withdrawn from the UK and Europe, emphasizing the need for alternative control methods. There is growing concern that climate change could alter trophic interactions and phenological events within agroecosystems. For example, warmer temperatures could lead to earlier pear flowering and pest emergence, as well as faster insect development rates and altered activity levels. If climate change impacts pear psyllid differently to natural enemies, then trophic mismatches could occur, impacting pest populations. This review aims to evaluate current strategies used in C. pyri management; discuss trophic interactions within this agroecosystem and highlight potential changes in the top-down and bottom-up control of C. pyri as a result of climate change. This review provides a recommended approach to pear psyllid management, identifies evidence gaps and outlines areas of future research
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Perennial flower margins reduce orchard fruit damage by rosy apple aphid, Dysaphis plantaginea (Homoptera: Aphididae)
Sown or natural flower strips are a commonly used management practice in agroecosystems and have been demonstrated to increase the abundance of predators of orchard pests. There is less evidence of the extent to which such strips can reduce pest damage in orchards.
Here we examined the effect of managed, perennial flower margins on fruit damage by an economically significant crop pest, Dysaphis plantaginea, rosy apple aphid, in conventional apple orchards over 2 years, compared to orchards without flower margins.
We found orchard flower margins reduced the percentage of apple trees with fruit damage by D. plantaginea, from 80% to 48%. In 2021, a period of severe infestation (65% of trees had fruit damage), there was reduced spread of D. plantaginea on infested apple trees and the number of trees with fruit damage was significantly reduced up to 50 m into orchards. During 2022, a period of lower infestation (25% of trees damaged), fruit damage was significantly reduced up to 10 m from the flower margin.
A significant reduction in predation of aphids from bait cards in flower margin compared with control orchards suggests specialists, rather than generalist predators, may be driving the positive effects of the margin on pest pressure. There was no significant effect of flower margins on abundance of important aphid predators, including Syrphidae (hoverflies) and Coccinellidae (ladybirds).
Synthesis and applications: To our knowledge, this study is the first to detect a reduction in fruit damage by pests at harvest in orchards with a flower margin. We highlight the potential for established perennial flower margins to deliver measurable, sustainable, D. plantaginea control benefits and provide insights into the optimal spatial arrangement of flower strips in orchards
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The potential of wildflower strips to enhance pollination services in sweet cherry orchards grown under polytunnels
Sweet cherry production benefits from insect pollination, but the extent to which wildflower strips can boost pollinator visitation under polytunnels is unknown. Wildflowers were established in alleyways between tree rows under polytunnels in 10 commercial cherry orchards. Their management involved either a single cut in September (Standard Wildflower Strips (SWS)) or being actively maintained to 20 cm with regular cutting (Actively Managed Wildflower Strips (AMWS)), compared with unsown Control Strips (CS). Flower visitors of cherry and wildflowers were recorded by visual observations for 3 years (2017–2019), while cherry production (quantity and quality) was assessed in 2019. In total, 67 visitor species were identified; managed commercial species (Apis mellifera and Bombus terrestris) made up ~74% of all records. During the cherry blossom period (anthesis), AMWS had the highest visitor density to cherry blossoms compared with CS and SWS but no significant difference in harvestable fruit was recorded. After anthesis, greater visitor density, diversity and richness were observed in both wildflower treatments compared with CS, being greatest in SWS, which was consistent with differences in floral communities between treatments. Although visitor density was not correlated with fruit set, pollinating insects were key for fruit yields and quality. Fruit set was ~17% from blossoms exposed to visitors compared with <1% when excluded. Furthermore, hand pollination resulted in ~32% fruit set, indicating greatest pollination deficits in CS (~50%) compared with AMWS (~28%) and SWS (~35%). Synthesis and applications. Sweet cherry is highly dependent on pollinators to underpin commercial yields, and pollination deficits exist under polytunnels. Growers should, therefore, reconsider their pollination strategies and look to combine effective pollinator management with polytunnel use to mitigate deficits; establishing and actively managing wildflowers in alleyways could enhance wild visitors and pollination
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The potential for wildflower interventions to enhance natural enemies and pollinators in commercial apple orchards is limited by other management practices
Modern fruit production has successfully increased yields and fruit quality to meet market demands mainly through intensification and the use of Plant Protection Products (PPPs). Due to the associated environmental impacts and consumers increasingly demanding food produced more sustainably, the tree fruit sector is seeking to reduce its reliance on PPPs. Despite intensification, apple production is still highly dependent on ecosystem services, including pest regulation and pollination. The aim of this study was to investigate the response of natural enemies and pollinators in commercial apple orchards to the provision of a wildflower habitat. It was hypothesised that the abundance and diversity of beneficial invertebrate species would be enhanced leading to an increased control of apple pests and enhanced pollination of apple blossom. We also investigated the effect of orchard pesticide toxicity on natural enemies and pest regulation services and how responses varied between apple cultivars (Jazz and Braeburn). The study was carried out in five orchards of each apple variety across Kent (UK), using a split-plot experimental design. At each site, a one-hectare orchard plot was established with wildflower strips in alleyways between rows of trees and compared with a one-hectare control plot where alleyways were managed conventionally with regular cutting. Responses of natural enemies and pollinators were recorded over a period of three and four years, respectively. The presence of wildflower strips did not contribute significantly towards the delivery of natural pest regulation or pollination services. However, hoverfly diversity and species richness were greater in orchards with wildflower strips, and whilst this was not associated with increased rates of pest regulation, such a response could potentially provide more resilient pest regulation and pollination services. Braeburn orchards had higher bee abundance, and pest predation rates, which were associated with a greater abundance of earwigs, compared to Jazz orchards. Of key significance for growers is that high values of cumulative pesticide toxicity negatively affected natural enemy populations, especially earwigs. If growers want to support natural enemies and wild pollinators in modern apple orchards following the principles of ecological intensification, they need to consider both the types and frequency of pesticide sprays used, in conjunction with interventions aimed at promoting beneficial invertebrates
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