Jean-Pierre Sarthou

Local and landscape determinants of pollen beetle abundance in overwintering habitats

1 The development of integrated pest management strategies requires that the semi‐natural habitats scattered across the landscape are taken into account. Particular determinants of insect pest abundance in overwintering habitats just before they migrate onto crops appear to be poorly known and of crucial importance for understanding patterns of crop colonization and pest population dynamics at the landscape scale. 2 The emergence of pollen beetle Meligethes aeneus F. was studied in grassland, woodland edge and woodland interior over a 3‐year survey in France using macro‐emergence traps. A suite of variables at the local and the landscape scale was assessed for each trap, aiming to identify potential relevant habitat indicators. The effects of habitat characteristics were evaluated using partial least square regressions. 3 It was found that M. aeneus can overwinter in all types of habitat but that particular habitat characteristics at the local and landscape scales may explain their abundance in overwintering sites more than the types of habitat: relative altitude, litter thickness, soil moisture and proximity to the previous years oilseed rape fields appear to be positively correlated with abundance of adults over the 3 years. 4 Hence, the abundance of emerged pollen beetles depends on both the landscape configuration of the previous years oilseed rape fields around overwintering sites and local habitat characteristics. Landscape configuration may determine population flow towards overwintering sites in the late summer, and local habitat characteristics may influence survival rates during the winter. The findings of the present study provide valuable insight into the role of semi‐natural habitats as a source of pests, patterns of crop colonization in the spring, and the influence of landscape on pollen beetle abundance.

How to Set Up a Research Framework to Analyze Social-Ecological Interactive Processes in a Rural Landscape

Interdisciplinary research frameworks can be useful in providing answers to the environmental challenges facing rural environments, but concrete implementation of them remains empirical and requires better control. We present our practical experience of an interdisciplinary research project dealing with non-industrial private forestry in rural landscapes. The theoretical background, management, and methodological aspects, as well as results of the project, are presented in order to identify practical key factors that may influence its outcomes. Landscape ecology plays a central role in organizing the project. The efforts allocated for communication between scientists from different disciplines must be clearly stated in order to earn reciprocal trust. Sharing the same nested sampling areas, common approaches, and analytical tools (GIS) is important, but has to be balanced by autonomy for actual implementation of field work and data analysis in a modular and evolving framework. Data sets are at the heart of the collaboration and GIS is necessary to ensure their long-term management and sharing. The experience acquired from practical development of such projects should be shared more often in networks of teams to compare their behavior and identify common rules of functioning.

Nutritional state of the pollen beetle parasitoid Tersilochus heterocerus foraging in the field

Many laboratory studies have demonstrated that parasitoids of various species depend on sugar sources such as nectar or honeydew. However, studies about nectar acquisition by parasitoids foraging in the field are scarce. Tersilochus heterocerus Thomson is one of the more abundant and widespread parasitoids of the pollen beetle (Meligethes aeneus F.) but nothing is known about the nutritional ecology of this species. In this study we examined the nutritional state of T. heterocerus at the time of emergence and at various time periods throughout the season while foraging in the field using high-performance anion-exchange chromatography. We found that: (i) T. heterocerus emerge with relatively small amounts of sugar, composed mainly of trehalose, glucose and fructose; (ii) the first parasitoids caught just after they appeared in the field at the beginning of oilseed rape flowering had already consumed significant amounts of sugar reserves; and (iii) the total amount of sugar at the end of flowering was always significantly higher than the total amount of sugar at the beginning of flowering. This study provides valuable insights into the acquisition of sugar in the field by the parasitoid T. heterocerus and suggests that nectar acquisition takes place in the oilseed rape field or in the surrounding landscape.

Crop–livestock integration beyond the farm level: a review

Paradoxically, the number of crop–livestock farms is declining across Europe, despite the fact that crop-livestock farms are theoretically optimal to improve the sustainability of agriculture. To solve this issue, crop–livestock integration may be organized beyond the farm level. For instance, local groups of farmers can negotiate land-use allocation patterns and exchange materials such as manure, grain, and straw. Development of such a collective agricultural system raises questions, rarely documented in the literature, about how to integrate crops and livestock among farms, and the consequences, impacts, and conditions of integrating them. Here, we review the different forms of crop–livestock integration beyond the farm level, their potential benefits, and the features of decision support systems (DSS) needed for the integration process. We identify three forms of crop–livestock integration beyond the farm level: local coexistence, complementarity, and synergy, each with increasingly stronger temporal, spatial, and organizational coordination among farms. We claim that the forms of integration implemented define the nature, area, and spatial configuration of crops, grasslands, and animals in farms and landscapes. In turn, these configurations influence the provision of ecosystem services. For instance, we show that the synergy form of integration promotes soil fertility, erosion control, and field-level biological regulation services through organizational coordination among farmers and spatiotemporal integration between crops, grasslands, and animals. We found that social benefits of the synergy form of integration include collective empowerment of farmers. We claim that design of the complementarity and synergy forms of crop–livestock integration can best be supported by collective participatory workshops involving farmers, agricultural consultants, and researchers. In these workshops, spatialized simulation modeling of crop–livestock integration among farms is the basis for achieving the upscaling process involved in integrating beyond the farm level. Facilitators of these workshops have to pay attention to the consequences on governance and equity issues within farmers groups.

Integrated management of damping-off diseases. A review

Damping-off is a disease that leads to the decay of germinating seeds and young seedlings, which represents for farmers one of the most important yield constraints both in nurseries and fields. As for other biotic stresses, conventional fungicides are widely used to manage this disease, with two major consequences. On the one hand, fungicide overuse threatens the human health and causes ecological concerns. On the other hand, this practice has led to the emergence of pesticide-resistant microorganisms in the environment. Thus, there are increasing concerns to develop sustainable and durable damping-off management strategies that are less reliant on conventional pesticides. Achieving such a goal requires a better knowledge of pathogen biology and disease epidemiology in order to facilitate the decision-making process. It also demands using all available non-chemical tools that can be adapted to regional and specific production situations. However, this still is not the case and major knowledge gaps must be filled. Here, we review up to 300 articles of the damping-off literature in order to highlight major knowledge gaps and identify future research priorities. The major findings are (i) damping-off is an emerging disease worldwide, which affects all agricultural and forestry crops, both in nurseries and fields; (ii) over a dozen of soil-borne fungi and fungus-like organisms are a cause of damping-off but only a few of them are frequently associated with the disease; (iii) damping-off may affect from 5 to 80% of the seedlings, thereby inducing heavy economic consequences for farmers; (iv) a lot of research efforts have been made in recent years to develop biocontrol solutions for damping-off and there are interesting future perspectives; and (v) damping-off management requires an integrated pest management (IPM) approach combining both preventive and curative tactics and strategies. Given the complex nature of damping-off and the numerous factors involved in its occurrence, we recommend further research on critical niches of complexity, such as seeds, seedbed, associated microbes and their interfaces, using novel and robust experimental and modeling approaches based on five research priorities described in this paper.

Practical improvements in soil redox potential (Eh) measurement for characterisation of soil properties. Application for comparison of conventional and conservation agriculture cropping systems.

The soil redox potential (Eh) can provide essential information to characterise soil conditions. In practice, however, numerous problems may arise regarding: (i) Eh determination in soils, especially aerobic soils, e.g. variations in the instrumentation and methodology for Eh measurement, high spatial and temporal Eh variability in soils, irreversibility of the redox reaction at the surface electrode, chemical disequilibrium; and (ii) measurement interpretation. This study aimed at developing a standardised method for redox potential measurement in soils, in order to use Eh as a soil quality indicator. This paper presents practical improvements in soil Eh measurement, especially regarding the control of electromagnetic perturbations, electrode choice and preparation, soil sample preparation (drying procedure) and soil:water extraction rate. The repeatability and reproducibility of the measurement method developed are highlighted. The use of Eh corrected at pH7, pe+pH or rH2, which are equivalent notions, is proposed to facilitate interpretation of the results. The application of this Eh measurement method allows characterisation of soil conditions with sufficient repeatability, reproducibility and accuracy to demonstrate that conservation agriculture systems positively alter the protonic and electronic balance of soil as compared to conventional systems.

Lack of Genetic Differentiation between Contrasted Overwintering Strategies of a Major Pest Predator Episyrphus balteatus (Diptera: Syrphidae): Implications for Biocontrol

Winter ecology of natural enemies has a great influence on the level and efficiency of biological control at spring. The hoverfly Episyrphus balteatus (DeGeer) (Diptera: Syrphidae) is one of the most important natural predators of crop aphids in Europe. Three different overwintering strategies coexist in this species which makes it a good model in order to study ecologically-based speciation processes. The purpose of this study was to determine whether E. balteatus populations with alternative overwintering strategies are genetically differentiated. To that aim, we developed 12 specific microsatellite markers and evaluated the level of neutral genetic differentiation between E. balteatus field populations that overwinter in the three different ways described in this species (i.e. migration, local overwintering at a pre-imaginal stage, and local overwintering at adult stage). Results showed a lack of neutral genetic differentiation between individuals with different overwintering strategies although there are strong ecological differences between them. All pair-wise FST values are below 0.025 and non-significant, and Bayesian clustering showed K = 1 was the most likely number of genetic clusters throughout our sample. The three overwintering strategies form one unique panmictic population. This suggests that all the individuals may have genetic material for the expression of different overwintering phenotypes, and that their commitment in one particular overwintering strategy may depend on environmental and individual factors. Consequently, the prevalence of the different overwintering strategies would be potentially modified by landscape engineering and habitat management which could have major implications for biological control.

Assessing the costs of measuring biodiversity: methodological and empirical issues

Abstract Organic and low-input farming practices are considered keystones for the conservation of biodiversity in semi-natural systems. Accordingly, attention to the assessment of the benefits stemming from these activities is increasing in order to provide a solid base for the adoption of agro-environmental incentives and to support their monitoring and evaluation. The evaluation of the positive effects of organic and low-input farming activities on biodiversity is limited mainly by the difficulty in proposing simple and widely-applicable indicators of biodiversity, and the substantial lack of data concerning the costs of measuring biodiversity – an essential element for the cost-effectiveness analysis of indicators. Moreover, the limited scientific literature available on indicator costs is based on ex-post analyses rather than on systematic data collection. The assessment of the costs of measuring biodiversity at the farm scale throughout Europe is one of the specific tasks of the BioBio project (UE-FP7). In this work, we discuss methodological aspects and preliminary results based on data gathered during fieldwork measurements of biodiversity in BioBio.

Conservation Biocontrol: Principles and Implementation in Organic Farming

Conventional agricultural systems have become more intensive and pesticide-dependent over the last few decades. The contamination of the environment by pesticides, the use of mineral fertilisers, and habitat loss in many agroecosystems have led to a drastic decrease in plant and animal biodiversity. Ecosystem services provided by functional biodiversity (e.g., pollination, biological pest control) have also been negatively impacted. Conservation biocontrol aims to preserve and promote natural enemies to enhance pest control, avoid pest outbreaks and reduce pesticide reliance. However, despite a consensus on the main underlying principles, intentional practical applications are still rare. It is assumed that the diversity of habitats and resources in agroecosystems enhances the diversity and/or effectiveness of the natural enemies of pests. In this article, we argue that organic farming (OF) provides a promising framework for increasing conservation biocontrol at field and farm scales in agricultural landscapes. We looked at most of the commonly used OF practices at different spatio-temporal scales and discussed their effects on pest populations, natural enemy communities and biocontrol in agroecosystems. Several OF management practices such as crop diversification, use of organic fertilisers, diversification of resource plants at the field or landscape scales and land-use management are examined in our review. We particularly focused on possible strategies to enhance pest control measures in two case studies (i.e., orchard and annual crops) and discussed how and at which scales such strategies should be implemented. In the end, we identified knowledge gaps and bottlenecks that, if resolved, would help to enhance conservation biocontrol and applications in OF systems that aim to maximise both bottom-up (through plants) and top-down (through natural enemies) processes.

Main Lessons Drawn from the Analysis of the Literature

Planting and destruction are the two main phases in cover crop management techniques. Their dates and implementation conditions play a key role in terms of the various functions targeted for these crops (nitrate-trapping, erosion prevention, weed control, effect on next crop, etc.). The analysis of the literature therefore focused on cover crop planting and destruction techniques. The aim was to identify the different methods and, if possible, their effectiveness with respect to the success of sowing and destruction. The issue of the implementation of these techniques by farmers was then examined by analysing the constraints in terms of organization of labour and implementation costs.