Effects of field and landscape variables on crop colonization and biological control of the cabbage root fly Delia radicum

Agriculture intensification has deeply modified agroecosystems from field to landscape scales. To achieve successful pest control using natural enemies, understanding species interactions over all scales remains a challenge. Using the cabbage root fly as a model, we studied whether field and landscape characteristics influenced colonization and infestation of broccoli fields by the pest and its control by natural enemies. We also determined whether species of different trophic level or host specialization would respond to environmental characteristics at the same spatial extent. During a multiple-species and multiple-spatial extent study in northwestern France, we recorded pest colonization and infestation in 68 fields, collected associated natural enemies and assessed crop damages. In each field, we considered management practices and characterized the surrounding landscape in 50–500 m-wide buffers. Our main findings are that Delia radicum and its main natural enemies respond to both field and landscape characteristics. Semi-natural areas supported both crop colonization by pests and natural enemy action. The pest and its enemies differed in their responses to field or landscape variables. Landscape elements such as field banks favored the movement of the pest while impeding the movement of some natural enemies. Pest pressure did not increase with the neighboring density of Brassica crops. The presence of natural enemies did not reduce crop damage but reduced pest emerging rates. Finally, specialist parasitoids responded to the landscape at larger spatial extents than generalists. These results outline the complexity of improving pest control through landscape management.     

Designing agricultural landscapes for natural pest control: a transdisciplinary approach in the Hoeksche Waard (The Netherlands)

The green–blue network of semi-natural non-crop landscape elements in agricultural landscapes has the potential to enhance natural pest control by providing various resources for the survival of beneficial insects that suppress crop pests. A study was done in the Hoeksche Waard to explore how generic scientific knowledge about the relationship between the spatial structure of the green–blue network and enhancement of natural pest control can be applied by stakeholders. The Hoeksche Waard is an agricultural area in the Netherlands, characterized by arable fields and an extensive network of dikes, creeks, ditches and field margins. Together with stakeholders from the area the research team developed spatial norms and design rules for the design of a green–blue network that supports natural pest control. The stakeholders represented different interests in the area: farmers, nature and landscape conservationists, water managers, and local and regional politicians. Knowledge about the spatial relationship among beneficial insects, pests and landscape structure is incomplete. We conclude that to apply scientific knowledge about natural pest control and the role of green–blue networks to stakeholders so that they can apply it in landscape change, knowledge transfer has to be transparent, area specific, understandable, practical and incorporate local knowledge.     

Organic farming affects the biological control of hemipteran pests and yields in spring barley independent of landscape complexity

Context

Hemipteran pests cause significant yield losses in European cereal fields. It has been suggested that local management interventions to promote natural enemies are most successful in simple landscapes that are dominated by large arable fields.

Objectives

We study how farming category (conventional, new and old organic fields) and landscape complexity affect pests, natural enemies and biological control services in spring barley. We further analyse if yields are related to pest infestation or biological control services.

Methods

The amount of pasture and the length of field borders were used to define landscape complexity around barley fields in Southern Sweden. Arthropods were sampled with an insect suction sampler and predation and parasitism services were estimated by field observations and inspections of pest individuals.

Results

Pest infestation was affected by landscape complexity, with higher aphid, but lower leafhopper numbers in more complex landscapes. Aphid predation was higher under organic farming and affected by effects on predator abundance and community composition independent of landscape complexity. Auchenorrhyncha parasitism was neither significantly affected by landscape complexity nor by farming category. Higher aphid predation rates and lower aphid densities were characteristic for organically managed fields with higher barley yields.

Conclusions

Our results suggest that it is possible to increase both aphid biological control services and barley yield via local management effects on predator communities independent of landscape complexity. However, the success of such management practices is highly dependent on the pest and natural enemy taxa and the nature of the trophic interaction.

     

Modeling invasive species spread in complex landscapes: the case of potato moth in Ecuador

Tropical mountains have a long history of human occupation, and although vulnerable to biological invasions, have received minimal attention in the literature. Understanding invasive pest dynamics in socio-ecological, agricultural landscapes, like the tropical Andes, is a challenging but timely issue for ecologists as it may provide developing countries with new tools to face increasing threats posed by these organisms. In this work, road rehabilitation into a remote valley of the Ecuadorian Andes constituted a natural experiment to study the spatial propagation of an invasive potato tuber moth into a previously non-infested agricultural landscape. We used a cellular automaton to model moth spatio-temporal dynamics. Integrating real-world variables in the model allowed us to examine the relative influence of environmental versus social landscape heterogeneity on moth propagation. We focused on two types of anthropogenic activities: (1) the presence and spatial distribution of traditional crop storage structures that modify local microclimate, and (2) long-distance dispersal (LDD) of moths by human-induced transportation. Data from participatory monitoring of pest invasion into the valley and from a larger-scale field survey on the Ecuadorian Andes allowed us to validate our model against actual presence/absence records. Our simulations revealed that high density and a clumped distribution of storage structures had a positive effect on moth invasion by modifying the temperature of the landscape, and that passive, LDD enhanced moth invasion. Model validation showed that including human influence produced more precise and realistic simulations. We provide a powerful and widely applicable methodological framework that stresses the crucial importance of integrating the social landscape to develop accurate invasion models of pest dynamics in complex, agricultural systems.     

Agricultural intensification exacerbates female-biased primary brood sex-ratio in tree swallows

Impacts of agriculture practices are documented at every ecosystem level from landscape structure to biodiversity. Birds are especially affected by agricultural modifications as shown by the decline of farmland species in Europe and North America. Few studies have assessed the effects of such modifications on individual characteristics directly influencing population dynamics. Several bird studies showed that sex-ratio may be adaptive and that mother condition affects the production of sons and daughters. However, little is known about the connections between environmental and individual characteristics on sex allocation. Here we quantified the variation in primary sex-ratio in tree swallows (Tachycineta bicolor) nesting in contrasted environments associated with agricultural intensification in southern Québec, Canada. We found that intensive agricultural practices affected female sex-ratio allocation in this area, resulting in more biased sex-ratio towards daughters throughout most of the hatching period. Yet, this bias towards daughters was reduced as the season progressed in the most intensively cultivated areas, suggesting that tree swallows have problems foreseeing the difficult growth and postfledging conditions that their nestlings will experience in such environments. Our results thereby support the hypothesis that intensive agricultural areas act as an ecological trap in our study system. We also found that effects of agricultural intensification on sex allocation differed among years and affected the relationships between sex-ratio allocation and hatching date. Our results suggest that agricultural intensification modifies female sex allocation in tree swallows, but the importance of the effects might vary among years and depend on timing of breeding.     

Landscape patterns and agriculture: modelling the long-term effects of human practices on Pinus sylvestris spatial dynamics (Causse Mejean, France)

This paper focuses on understanding human impact on landscape. Both ecological and human practices are analysed as interacting processes. An agent-based model integrating biological and historical knowledge is used to analyse the pattern of Scots Pine encroachment in a French Mediterranean upland. In the STIPA model, pine trees are autonomous agents and a cellular automaton simulates land-use. We test the effects of shifting cultivation on tree establishment at the landscape scale. This allows us to understand how agropastoral practices patterned this area from the 17th to 19th century: simulations show the importance of shifting cultivation in limiting woodland progression. Fallow duration linked to environmental heterogeneity is a significant factor for explaining pine dynamics and landscape patterning at the scale of the study region. We put this result in perspective with current rangeland management policies that often consider grazing as the most relevant tool for open landscape maintenance. Our results also show the importance of taking into account time-scale effects when linking landscape patterns to agricultural systems.     

Effects of landscape composition on spread of an herbicide-resistant weed

Widespread adoption of genetically modified glyphosate-resistant (GR) crops in the US has dramatically changed the agricultural landscape to one that selects for establishment and spread of weedy species resistant to glyphosate, a commonly applied herbicide. Weed species that possess the means to readily spread across the landscape will be contained by weed management strategies that limit weed establishment and prevent seed set. An empirically-derived simulation model was developed to explore GR Conyza canadensis spread in relation to characteristics of the agricultural landscape. C. canadensis seeds are carried in the wind and move among fields and therefore, access high quality habitat (GR crops) at long distances. The baseline scenario was the current GR adoption levels in many US agricultural landscapes with corn and soybean rotated annually. Alternate scenarios examined the interacting effects of management uniformity (GR crop adoption) and increased landscape richness (three crops: corn, soybean, alfalfa, instead of two), over a 10 year simulation period. When landscape uniformity increased (increased GR corn adoption), 3× more fields would be infested with the resistant biotype and a specific field would have up to 24% greater likelihood of being infested compared to the current GR crop adoption levels. Increased landscape richness (adding alfalfa as a third crop) slightly decreased GR C. canadensis abundance. Reduced GR management uniformity by way of reducing GR soybeans to half their current adoption levels had the greatest impact on spread and prevented GR C. canadensis from reaching high abundance. Large-scale reliance on glyphosate for weed management has increased high-fitness habitat and will result in rapid spread of glyphosate-resistant weeds. Without significant reductions of glyphosate use and without spatial coordination of weed and crop management practices, GR weeds will continue to spread rapidly and impact agricultural practices in areas reliant on glyphosate.     

Local and landscape effects of agricultural intensification on Carabid community structure and weed seed predation in a perennial cropping system

Context

The effects of agricultural intensification on service-providing communities remain poorly studied in perennial cropping systems. However, such systems differ greatly from annual cropping systems in terms of spatio-temporal dynamics and levels of disturbance. Identifying how land use changes at different scales affect communities and ecosystem services in those habitats is of major importance.

Objectives

Our objectives were to examine the effects of local and landscape agricultural intensification on ground beetle community structure and weed seed predation services.

Methods

We examined the effects of local vegetation management and landscape context on ground beetle community structure and weed seed predation in 20 vineyards of southwestern France in 2013 and 2014. Vineyards were selected along a landscape complexity gradient and experienced different management of local vegetation.

Results

The activity-density of ground beetles decreased with increasing landscape complexity while species richness and evenness remained unchanged. Phytophagous and macropterous species dominated ground beetle communities. Seed predation was positively related to the activity-density of one species, Harpalus dimidiatus, and was not affected by local management or landscape context. We found that within-year temporal diversity in ground beetle assemblages increased with landscape complexity.

Conclusions

Our study shows that increasing the proportion of semi-natural habitats in vineyard landscapes enhances the temporal diversity of ground beetles. However, we also found that measures targeting specific species delivering biological control services are a reasonable strategy if we are to maximize natural pest control services such as weed seed regulation to support crop production and reduce agrochemical use.

     

Landscape agronomy: a new field for addressing agricultural landscape dynamics

Landscape dynamics increasingly challenge agronomists to explain how and why agricultural landscapes are designed and managed by farmers. Nevertheless, agronomy is rarely included in the wide range of disciplines involved in landscape research. In this paper, we describe how landscape agronomy can help explain the relationship between farming systems and agricultural landscape dynamics. For this, we propose a conceptual model of agricultural landscape dynamics that illustrates the specific contribution of agronomy to landscape research. This model describes the relationship between three elements: farming practices, landscape patterns and natural resources. It can stimulate agronomists to deal with research issues in agricultural landscape dynamics and enhance the interdisciplinary integration of farming systems in wider landscape research. On these premises, we discuss the main research issues that will benefit from an active involvement of agronomy, to understand, but also to assess landscape dynamics and to design relevant decision support systems.     

大数据时代山东农业病虫害监测预警体系建设

在大数据时代,海量的数据资源是推动经济发展和社会进步的基石,丰富、透明、完善的农业大数据资源是加快农业信息化建设步伐的前提,先进、有序、完备的农业病虫害监测预警体系是服务绿色农业发展的支撑。该研究试图在研究国内外农业病虫害监测预警体系的基础上,在农业专家的指导下,进行大数据时代农业病虫害监测预警体系构建。山东农业病虫害监测预警体系的建设应主动适应大数据时代的发展需求,分步构建病虫害监测预警体系,分层划分病虫害数据中心工作,合理布局病虫害数据采集站点,科学制定病虫害监测预警任务,共建共享病虫害监测数据信息,有效加强病虫害联合监测预警,努力研发病虫害智能识别终端,为发展现代高效农业提供坚实的保障。     

Effects of landscape structure on avian-mediated insect pest control services: a review

Context

Despite increasing evidence that landscape composition and configuration strongly influence the community structure of potential pest-regulators, landscape structure has seldom been explicitly linked with the rate and magnitude of pest-control services.

Objectives and methods

We conducted a systematic literature review evaluating 158 relevant studies to: (1) characterize our existing understanding of the empirical relationships between landscape structure and avian-mediated insect pest control services in agricultural systems, (2) identify gaps in our current understanding, and (3) develop a conceptual model of landscape structural influences on avian-mediated pest control.

Results and discussion

We found on-farm pest suppression by birds was often higher in landscapes with higher native habitat cover, higher compositional heterogeneity, and in agricultural patches in closer proximity to native habitats. We identified more than 200 bird species that provide pest control services across both temperate and tropical regions. While most avian predators are habitat-generalist species, a substantial fraction of pest control services in tropical regions was mediated by habitat-dependent species, suggesting a link between conservation management and maintenance of pest control services. We identified a three-part research agenda for future investigations of the relationships between landscape structure and avian-mediated pest control, focusing on an improved understanding of mechanisms related to: (1) predator–prey interactions and landscape modulation of trophic relationships, (2) bird dispersal ability and landscape connectivity, and (3) cross-habitat spillover of habitat-dependent avian predators.

Implications

These findings can be applied to efforts to manage and design landscapes capable of supporting both biodiversity and ecosystem services.

     

黔北梨园主要病虫害的发生动态和演变原因及防治

通过对黔北梨园主要病虫害的调查研究,分析近些年来该地区梨树病虫种群的发生动态和演变原因,提出加强农业措施,积极开展物理、生物防治,合理使用化学防治的对策。     

不同颜色粘虫板对葡萄园昆虫的诱集效应

为筛选出对葡萄害虫诱集效果好的粘虫板,选用黄色、蓝色、白色、紫色、绿色、红色、黑色和荧光色8种颜色的粘虫板对葡萄园内昆虫进行诱集试验。结果表明,共诱到昆虫7目18科22种,主要害虫有蓟马、蚜虫和叶蝉,其中蓟马数量占到昆虫总量的88.96%,天敌昆虫主要有寄生蜂、捕食性瓢虫、食蚜蝇和东亚小花蝽。紫板、蓝板和白板对蓟马的诱集效果强,黄板、荧光板和绿板次之,红板和黑板效果差;黄板对蚜虫诱集效果强,绿板和荧光板次之,黄板与其他色板之间差异显著;黄板、荧光板和绿板对叶蝉的诱集效果好,3种色板与蓝板之间差异不显著、与其他色板差异显著。白板、蓝板和黄板诱集到的天敌数量最多,占所有颜色粘虫板诱集天敌总量的69%左右。试验期间诱集到的昆虫益害比为0.036,各色板的益害比依次为黑色>荧光色>绿色>红色>黄色>白色>蓝色>紫色,其中紫板的益害比最低,仅为0.011。结合各色板的诱虫效果和益害比进行综合分析,建议选用紫板对蓟马进行诱杀,适时适量选择性使用黄板对蚜虫、叶蝉等进行诱杀。     

高山萝卜地下害虫种类及发生规律

2010～2013 年，在海拔1 800 m 的湖北省长阳土家族自治县火烧坪乡萝卜生产基地，通过田间调查和黑光灯诱集相结合的方法研究高山萝卜地下害虫种类及发生规律。结果显示：高山萝卜常见地下害虫有4 目7 科11 种，其中以小地老虎〔Agrotis ypsilon（Rottemberg）〕、黄曲条跳甲〔Phyllotreta striolata（Fabricius）〕和灰地种蝇〔Delia platura（Meigen）〕为害最重。高山萝卜地下害虫发生程度与季节有关，小地老虎的为害集中于6 月中下旬及7 月中旬；黄曲条跳甲的为害集中于8 月；灰地种蝇的为害集中于5 月。高山萝卜地下害虫的防治应以小地老虎、灰地种蝇和黄曲条跳甲作为重点。     

莲藕食根金花虫为害特性及防治方法

莲藕食根金花虫是莲藕的重要害虫之一,对莲藕食根金花虫的分类地位、形态学特征、为害特点、发生规律等进行了阐述,并介绍了其生物、农业、化学防治方法,以期为有效抑制该虫的为害提供参考。     

Quantifying the agricultural landscape and assessing spatio-temporal patterns of precipitation and groundwater use

Quantitative agricultural landscape indices are useful to describe functional relationships among climatic conditions, groundwater dynamics, soil properties and agricultural land use for mathematical models. We applied methods of regression statistics, variance component estimation and a Geographical Information System (GIS) to construct indices describing crops and soils and to establish functional relationships among these variables. This paper describes the development of indices and the partitioning of the spatial and temporal variation in groundwater models using the data from Tulare County, California, which was selected as the study area. Indices of ground surface elevation, total crop water demand, soil water infiltration rate, and soil production index explain 91% of the variation in average spring groundwater level. After relating spatial patterns of groundwater use to indices of crop and soil properties, we found that mean groundwater use is positively related to total crop water demand and soil water infiltration rate while the variation in groundwater use was negatively correlated with the crop water demand and soil water infiltration rate and positively related to soil water holding capacity. The spatial variation in groundwater use was largely influenced by crops and soil types while the temporal variation was not. We also found that groundwater use increased exponentially with decreasing annual precipitation for most townships. Based on these associations, groundwater use in each township can be forecast from relative precipitation under current methods of agricultural production. Although groundwater table depth is strongly affected by topography, the statistically significant indices observed in the model clearly show that agricultural land use influences groundwater table depth. These simple relationships can be used by agronomists to make water management decisions and to design alternative cropping systems to sustain agricultural production during periods of surface water shortages.     

A mathematical approach to simulate spatio-temporal patterns of an insect-pest,the corn rootworm Diabrotica speciosa (Coleoptera: Chrysomelidae) in intercropping systems

We report on the use of a spatially explicit model and clustering analysis in order to investigate habitat manipulation as a strategy to regulate natural population densities of the insect-pest Diabrotica speciosa. Habitat manipulation involved four major agricultural plants used as hosts by this herbivore to compose intercropping landscapes. Available biological parameters for D. speciosa on bean, soybean, potato and corn obtained under laboratory conditions were used to group the homogeneous landscapes, composed by each host plant, by a similarity measure of host suitability either for larval survival and development, and adult survival and fecundity. The results pointed corn as the most dissimilar culture. Therefore, intercropping corn with any other crop system tested could reduce insect spread through landscape. This was proved using a cellular automata model which simulate the physiological and behavioural traits of this insect, and also different spatial configurations of the intercropping. Spatio-temporal patterns obtained by simulations demonstrated that the availability of corn bordering the field edge, which are areas more likely to invasion, is key for insect population control.     

Landscape changes and ecological studies in agricultural regions,Québec,Canada

Most landscape definitions in the western world are based on soil, climatic, or physiographic features and do not integrate humans as an integral part of the landscape. We present an approach where landscape types have been delineated in southern Québec, Canada based on current land use where anthropogenic and agricultural activities are concentrated as a practical application of the holistic approach in landscape definition. Landsat-TM satellite images were classified and the 27 habitat classes were regrouped into 5 general land cover classes (cash crop, dairy farming, forest, anthropogenic, wetlands) and overlaid onto soil landscape polygons to characterize natural boundary units. Cluster analyses were used to aggregate these polygons into seven agricultural types of land scape forming a gradient from urban and high-intensity cash crop farming activities to landscapes dominated by a mosaic of agriculture and forested areas. Multivariate analyses of raw data and of socio-economic and farming practices variables were used to describe the defined types of landscape and these were projected over three established land classification systems of southern Québec (Canadian ecoregions, North American Bird Conservation Initiative regions and Corn Heat Unit regions) to compare their similarity in terms of land cover and for planning of future ecological studies. Because agricultural landscapes are highly dynamic, they are bound to undergo changes in the near future. Our landscape delineation may serve as an experimental setup where land scape dynamics and wildlife populations and community structures could be monitored. Because the information we used to delineate and characterize agricultural landscape types is readily available in other countries, our approach could easily be adapted to similar data sources under and a wide variety of landscape types. This revised version was published online in July 2006 with corrections to the Cover Date.     

Land cover and climate changes drive regionally heterogeneous increases in US insecticide use

Context

Global environmental change is expected to dramatically affect agricultural crop production through a myriad of pathways. One important and thus far poorly understood impact is the effect of land cover and climate change on agricultural insect pests and insecticides.

Objectives

Here we address the following three questions: (1) how do landscape complexity and weather influence present-day insecticide use, (2) how will changing landscape characteristics and changing climate influence future insecticide use, and how do these effects manifest for different climate and land cover projections? and (3) what are the most important drivers of changing insecticide use?

Methods

We use panel models applied to county-level agriculture, land cover, and weather data in the US to understand how landscape composition and configuration, weather, and farm characteristics impact present-day insecticide use. We then leverage forecasted changes in land cover and climate under different future scenarios to predict insecticide use in 2050.

Results

We find different future scenarios—through modifications in both landscape and climate conditions—increase the amount of area treated by ~ 4–20% relative to 2017, with regionally heterogeneous impacts. Of note, we report large farms are more influential than large crop patches and increased winter minimum temperature is more influential than increased summer maximum temperature. However, our results suggest the most important determinants of future insecticide use are crop composition and farm size, variables for which future forecasts are sparse.

Conclusions

Both landscape and climate change are expected to increase future insecticide use. Yet, crop composition and farm size are highly influential, data-poor variables. Better understanding of future crop composition and farm economics is necessary to effectively predict and mitigate increases in pesticide use.