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Cultivar mixtures have been proposed as a way to increase diversity and thereby improve plant production, but our understanding of the effects of mixing cultivars on crop diseases and resource-use efficiency remains fragmentary. We performed a meta-analysis to assess the effects of cultivar mixtures on crop yield, yield stability, resource-use efficiency, and disease severity compared with monocultures of twelve major crops. We found that, overall, mixing of cultivars increased crop yield by 3.82%. Yield gains from mixing cultivars were highest in rice (+16.1%), followed by maize (+8.5%), and were lowest in barley (+0.9%) and sorghum (no increase). Temporal yield stability increased with the number of cultivars in the mixtures. Overall, mixing cultivars increased crop biomass, leaf area index, photosynthetic rate, and Water-use efficiency by 5.1, 7.2, 8.5 and 4.3%, respectively, and decreased disease incidence by 24.1%. Cultivar mixtures were more effective in mitigating diseases and increasing yields in studies performed at lower latitudes, higher mean annual temperatures, and higher mean annual precipitation. Our study complements and adds to previous research, indicating that cultivar mixtures reduce crop losses to disease and enhance resource-use efficiency compared with monocultures globally. We conclude that the targeted use of cultivar mixtures with appropriate management practices can reduce resource and pesticide inputs while maintaining high yields, thereby promoting sustainable and productive agriculture. [ABSTRACT FROM AUTHOR]

Behavioral manipulation (BM) is a multimodal control approach based on the interference with the stimuli mediating insect perception and interaction with the surroundings. BM could represent a win–win strategy for the management of vector-borne plant pathogens as the bacterium Xylella fastidiosa, since it could reduce the number of vectors alighting on host plants and, consequently, the chances for transmission to occur. In this review, we summarized current knowledge and highlighted gaps in information on (i) how insect vectors of X. fastidiosa in general, and more specifically the meadow spittlebug Philaenus spumarius, locate and accept the host plant; and (ii) how behavioral manipulation techniques could be applied to disrupt the vector–host plant interaction. Finally, we discussed how diverse BM strategies could be combined with other integrated pest management tools to protect olive groves from inoculation with the fastidious bacterium. [ABSTRACT FROM AUTHOR]

Ground beetles (carabids) constitute an important functional component of biodiversity in agroecosystems, mainly because of their role as predators of pests, but also as consumers of weed seeds and as prey to other organisms. Over the past few decades, there has been a marked and continuous decline of ground beetles in Europe, and many species of this insect family are threatened by intensive agricultural practices. The effect of soil tillage, a standard technique in arable farming, on carabids has been investigated in many experimental studies. However, there is currently no clear and differentiated picture of how ground beetles are affected by tillage operations in direct and indirect ways. In this review, we narrow this gap of knowledge and show that the effects of intensive tillage on ground beetles—especially the use of mouldboard ploughing—are extremely variable. Nonetheless, on balance across multiple studies, greater tillage intensity tends to have a negative effect on abundance, species richness, and diversity. The observed variability may partly be attributed to a change in species-specific food availability or habitat conditions, induced by tillage. Tillage effects on dominant species tend to have a strong impact on total carabid abundance. The high variability of carabid responses to tillage is also a consequence of various modifying factors such as cover cropping, rotations, and variations in weed control associated with tillage. Because different modes of tillage tend to affect different carabid species, the diversification of tillage operations within a farm or region may contribute to the overall diversity of carabid communities. [ABSTRACT FROM AUTHOR]

Purpose: Mixtures of cover crops are gaining importance in farming systems. While complementarity between species is a potentially important mechanism underlying mixture benefits, there is little quantitative evidence about complementarity of root growth. Therefore, we aimed to gain detailed knowledge about mixture effects of specific root traits. Methods: Blue lupin (Lupinus angustifolius L.) and winter rye (Secale cereale L.) were grown as sole and intercrops in a two-year organically managed field experiment in Germany. Crops were analysed for shoot biomass and nutrient uptake as well as for root mass density (RMD), root length density (RLD) and specific root length (SRL). We used Fourier transform infrared (FTIR) spectroscopy to discriminate the root mass species-specifically in the mixtures. Results: In the shoot, overyielding was only found for N and P uptake in the 75:25 mixture of lupin and rye, whereas positive mixture effects of RLD, RMD, and root mass complementarity occurred only in the 50:50 mixture in one year. Consistently positive mixture effects of SRL were found. Root biomass proportion of rye was higher in topsoil, that of lupin higher in subsoil. Vertical niche differentiation in RMD between sole crops and mixtures was not observed. Conclusion: Among all root traits analysed, consistent mixture effects were observed only for SRL. Mechanisms behind mixture effects of root traits need further research. FTIR spectroscopy discriminated intercrop root mass well. Discrimination of mixture partners' root length would help to better understand complementarity of root growth in mixtures. [ABSTRACT FROM AUTHOR]

Different diversification practices have the potential to reduce pests and therefore pesticide use. Yet, their integration at the agroecosystem level and the evaluation of their multifunctional effects remain limited. Through a two-year field experiment conducted in Germany, we tested whether associating intercropping (faba bean-wheat, followed by breadseed poppy-barley) with pluriannual wildflower strips strengthens the biological regulation of aphid pests and weeds, and enhances cropping system productivity. The contribution of flowering weeds to conservation biological control was also analysed. Aphid but also predator colonization and predation rates on bean and poppy were consistently lower in intercropping compared to sole cropping. Wildflower strips enhanced aphid predation in bean-wheat intercropping, and further reduced aphid colonization at 10 m distance but not at 20 m in poppy-barley intercropping. Weed biomass was consistently reduced in intercropping compared to sole cropping bean and poppy, and did not significantly affect bean and poppy yields in intercropping. The cover of one flowering weed species, Matricaria recutita, was negatively correlated to aphid colonization and positively correlated to predation rate. Matricaria recutita flowers were also visited more often by predatory hoverflies in plots adjacent to wildflower strips. Finally, land equivalent ratio was consistently higher than 1, and the highest in bean-wheat intercropping associated to wildflower strips. The study demonstrates the benefits of associating wildflower strips to intercropping to strengthen biological control and cropping system productivity. Flowering weeds, maintained at an acceptable level through intercropping, turn out to be relevant functional biodiversity in interacting with wildflower strips for conservation biological control. [ABSTRACT FROM AUTHOR]

Current use of mineral nitrogen (N) fertilizers is unsustainable because of its high fossil energy requirements and a considerable enrichment of the biosphere with reactive N. Biological nitrogen fixation (BNF) from leguminous crops is the most important renewable primary N source, especially in organic farming. However, it remains unclear to which degree BNF can sustainably replace mineral N, overcome the organic to conventional (O:C) yield gap and contribute to food security. Using an agronomic modelling approach, we show that in high-yielding areas farming systems exclusively based on BNF are unlikely to sustainably reach yield levels of mineral-N based systems. For a high reference wheat yield (7.5 t ha−1) and a realistic proportion of fodder legumes in the rotation (33%) even optimistic levels of BNF (282 kg N ha−1), resulted in an O:C ratio far below parity (0.62). Various constraints limit the agricultural use of BNF, such as arable land available for legumes and highly variable performance under on-farm conditions. Reducing the O:C yield gap through legumes will require BNF performance to be increased and N losses to be minimised, yet our results show that limits to the productivity of legume-based farming systems will still remain inevitable. [ABSTRACT FROM AUTHOR]

Background and aims: Intercrops offer multiple advantages over sole crops. The aim of our study was to characterize root growth and interactions in spring wheat/faba bean intercrops to better understand belowground interactions that govern resource capture.A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities, defining three intercropping designs. Destructive root coring was conducted (0–100 cm) in the intercrops and sole crops at two development stages. FTIR spectroscopy was used to discriminate the species’ root masses. The plant-plant interaction index was calculated to represent the belowground interactions.A negative impact of intercropping on total root mass was observed in the treatment with high sowing density in both stages. For the fully and partial replacement design treatments, plant-plant facilitation was more pronounced than competition in all layers. Competition dominated root growth in the treatment with high sowing density in both stages. Lower sowing densities encouraged deep root growth of wheat (both cultivars) in intercropping. The early root growth in depth and in density of one spring wheat cultivar impacted negatively faba bean root growth. Intercropping resulted in a grain yield advantage in both fully and only one partial replacement design treatment.In the intercrops, total root mass and plant-plant interactions were affected more by sowing density than by the spring wheat cultivar. Understanding the effect of sowing density on root growth in intercropping can help to support the design of sustainable intercropping systems.Materials and methods: Intercrops offer multiple advantages over sole crops. The aim of our study was to characterize root growth and interactions in spring wheat/faba bean intercrops to better understand belowground interactions that govern resource capture.A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities, defining three intercropping designs. Destructive root coring was conducted (0–100 cm) in the intercrops and sole crops at two development stages. FTIR spectroscopy was used to discriminate the species’ root masses. The plant-plant interaction index was calculated to represent the belowground interactions.A negative impact of intercropping on total root mass was observed in the treatment with high sowing density in both stages. For the fully and partial replacement design treatments, plant-plant facilitation was more pronounced than competition in all layers. Competition dominated root growth in the treatment with high sowing density in both stages. Lower sowing densities encouraged deep root growth of wheat (both cultivars) in intercropping. The early root growth in depth and in density of one spring wheat cultivar impacted negatively faba bean root growth. Intercropping resulted in a grain yield advantage in both fully and only one partial replacement design treatment.In the intercrops, total root mass and plant-plant interactions were affected more by sowing density than by the spring wheat cultivar. Understanding the effect of sowing density on root growth in intercropping can help to support the design of sustainable intercropping systems.Results: Intercrops offer multiple advantages over sole crops. The aim of our study was to characterize root growth and interactions in spring wheat/faba bean intercrops to better understand belowground interactions that govern resource capture.A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities, defining three intercropping designs. Destructive root coring was conducted (0–100 cm) in the intercrops and sole crops at two development stages. FTIR spectroscopy was used to discriminate the species’ root masses. The plant-plant interaction index was calculated to represent the belowground interactions.A negative impact of intercropping on total root mass was observed in the treatment with high sowing density in both stages. For the fully and partial replacement design treatments, plant-plant facilitation was more pronounced than competition in all layers. Competition dominated root growth in the treatment with high sowing density in both stages. Lower sowing densities encouraged deep root growth of wheat (both cultivars) in intercropping. The early root growth in depth and in density of one spring wheat cultivar impacted negatively faba bean root growth. Intercropping resulted in a grain yield advantage in both fully and only one partial replacement design treatment.In the intercrops, total root mass and plant-plant interactions were affected more by sowing density than by the spring wheat cultivar. Understanding the effect of sowing density on root growth in intercropping can help to support the design of sustainable intercropping systems.Conclusion: Intercrops offer multiple advantages over sole crops. The aim of our study was to characterize root growth and interactions in spring wheat/faba bean intercrops to better understand belowground interactions that govern resource capture.A field experiment was conducted with one faba bean cultivar and two spring wheat cultivars sown at three sowing densities, defining three intercropping designs. Destructive root coring was conducted (0–100 cm) in the intercrops and sole crops at two development stages. FTIR spectroscopy was used to discriminate the species’ root masses. The plant-plant interaction index was calculated to represent the belowground interactions.A negative impact of intercropping on total root mass was observed in the treatment with high sowing density in both stages. For the fully and partial replacement design treatments, plant-plant facilitation was more pronounced than competition in all layers. Competition dominated root growth in the treatment with high sowing density in both stages. Lower sowing densities encouraged deep root growth of wheat (both cultivars) in intercropping. The early root growth in depth and in density of one spring wheat cultivar impacted negatively faba bean root growth. Intercropping resulted in a grain yield advantage in both fully and only one partial replacement design treatment.In the intercrops, total root mass and plant-plant interactions were affected more by sowing density than by the spring wheat cultivar. Understanding the effect of sowing density on root growth in intercropping can help to support the design of sustainable intercropping systems. [ABSTRACT FROM AUTHOR]

In the face of a changing climate, yield stability is becoming increasingly important for farmers and breeders. Long-term field experiments (LTEs) generate data sets that allow the quantification of stability for different agronomic treatments. However, there are no commonly accepted guidelines for assessing yield stability in LTEs. The large diversity of options impedes comparability of results and reduces confidence in conclusions. Here, we review and provide guidance for the most commonly encountered methodological issues when analysing yield stability in LTEs. The major points we recommend and discuss in individual sections are the following: researchers should (1) make data quality and methodological approaches in the analysis of yield stability from LTEs as transparent as possible; (2) test for and deal with outliers; (3) investigate and include, if present, potentially confounding factors in the statistical model; (4) explore the need for detrending of yield data; (5) account for temporal autocorrelation if necessary; (6) make explicit choice for the stability measures and consider the correlation between some of the measures; (7) consider and account for dependence of stability measures on the mean yield; (8) explore temporal trends of stability; and (9) report standard errors and statistical inference of stability measures where possible. For these issues, we discuss the pros and cons of the various methodological approaches and provide solutions and examples for illustration. We conclude to make ample use of linking up data sets, and to publish data, so that different approaches can be compared by other authors and, finally, consider the impacts of the choice of methods on the results when interpreting results of yield stability analyses. Consistent use of the suggested guidelines and recommendations may provide a basis for robust analyses of yield stability in LTEs and to subsequently design stable cropping systems that are better adapted to a changing climate. [ABSTRACT FROM AUTHOR]

Purpose: The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity.Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used.Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity.Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.Methods: The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity.Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used.Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity.Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.Results: The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity.Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used.Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity.Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed.Conclusion: The current knowledge of belowground interactions in intercropping systems is limited due to methodological constraints. The current study aimed to investigate cereal-brassica and cereal-legume-brassica cover crop mixtures regarding mixture effects on root and shoot biomass as well as root traits, vertical root niche differentiation, and complementarity.Sole crops and two- and three-species-mixtures of winter rye (Secale cereale L.), crimson clover (Trifolium incarnatum L.), and oil radish (Raphanus sativus L. var. oleiformis Pers.) were grown in Germany in a two-year organic field experiment. Root traits were analysed using the monolith method. For discrimination of species root mass Fourier transform infrared (FTIR) spectroscopy was used.Oil radish dominated mixtures above- and belowground. Oil radish and its mixtures had highest root length density (RLD) and root mass density (RMD) in subsoil. Rye had highest root biomass and RLD in topsoil. Clover was uncompetitive and had low RLD and RMD. Large but non-significant mixture effects occurred in the shoot, especially for shoot nutrient uptake. Mixture effects were positive for RLD and RMD in subsoil and positive for specific root length (SRL) throughout the whole profile. There was no clear evidence for vertical root niche differentiation and root mass complementarity.Oil radish as a mixing partner increased rooting in subsoil. When comparing mixtures and sole crops, morphological changes, i.e. higher SRL in mixtures, were found. Contrary to expectations, changes in root allocation patterns, such as vertical niche differentiation or complementarity of root mass, were not observed. [ABSTRACT FROM AUTHOR]

1 Soil moisture in % of plant-available water capacity under grass on a sandy loam between 0 and 60 cm soil depth at the nearby (12 km) weather station from the German Meteorological Service at Cologne Bonn Airport in the period from two weeks before sowing until biomass sampling of cover crops for both experimental years The original article has been corrected. B Correction to: Plant and Soil b https://doi.org/10.1007/s11104-022-05366-9 The original version of the article unfortunately contained an error. [Extracted from the article]

The pollen beetle ( Meligethes aeneus) is a major pest of oilseed rape ( Brassica napus) at the inflorescence stage and is well known to prefer colours called yellow by human observers over many other colours. While commercial cultivars of oilseed rape have yellow flowers, little is known about the potential to manipulate host plant location and reduce subsequent infestation by this pest through variation in flower colour. We investigated the responses of pollen beetles to flowers of a white-petalled oilseed rape variety that had been dyed different colours in semi-field arena and field experiments. Flowers dyed blue or red were less heavily infested than those dyed yellow or the white flowers, indicating that blue and red flowers were less attractive than yellow and white ones. This response was most likely due to differences in petal colour because olfactometer studies showed that beetle responses to the odours of the coloured treatments did not differ. The comparatively high infestation of untreated white flowers is interpreted as a consequence of their high UV reflectance; the presence of a UV receptor in M. aeneus is suggested, and its role in visually guided insect-plant interactions in this species described. The potential for manipulation of petal colour in control strategies for the pollen beetle is discussed. [ABSTRACT FROM AUTHOR]

The circulation of seed among farmers is central to agrobiodiversity conservation and dynamics. Agrobiodiversity, the diversity of agricultural systems from genes to varieties and crop species, from farming methods to landscape composition, is part of humanity's cultural heritage. Whereas agrobiodiversity conservation has received much attention from researchers and policy makers over the last decades, the methods available to study the role of seed exchange networks in preserving crop biodiversity have only recently begun to be considered. In this overview, we present key concepts, methods, and challenges to better understand seed exchange networks so as to improve the chances that traditional crop varieties (landraces) will be preserved and used sustainably around the world. The available literature suggests that there is insufficient knowledge about the social, cultural, and methodological dimensions of environmental change, including how seed exchange networks will cope with changes in climates, socio-economic factors, and family structures that have supported seed exchange systems to date. Methods available to study the role of seed exchange networks in the preservation and adaptation of crop specific and genetic diversity range from meta-analysis to modelling, from participatory approaches to the development of bio-indicators, from genetic to biogeographical studies, from anthropological and ethnographic research to the use of network theory. We advocate a diversity of approaches, so as to foster the creation of robust and policy-relevant knowledge. Open challenges in the study of the role of seed exchange networks in biodiversity conservation include the development of methods to (i) enhance farmers' participation to decision-making in agro-ecosystems, (ii) integrate ex situ and in situ approaches, (iii) achieve interdisciplinary research collaboration between social and natural scientists, and (iv) use network analysis as a conceptual framework to bridge boundaries among researchers, farmers and policy makers, as well as other stakeholders. [ABSTRACT FROM AUTHOR]

Organic agriculture regulations, in particular European regulation EC 889/2008, prescribe the use of organically produced seed. For many cultivated plants, however, organic seed is often not available. This is mainly because investment in organic plant breeding and seed production has been low in the past. To bridge the gap between organic seed supply and demand, national and European regulations define certain circumstances under which organic producers are permitted to use non-organically produced seed. While the organic sector currently depends on these concessions, they also threaten to impede a further increase in the demand for organic seed, thereby potentially restraining present and future investment in organic seed production and plant breeding. We review the current status of the organic seed regulations framework by analysing key issues such as the role of the national derogation regimes, the role of Expert Groups, databases and seed prices. Key points are that (a) the situation of the organic seed sector has improved over the last few years; however, (b) reporting on organic seed to the EU by different countries needs to be harmonised; (c) the success of the organic seed sector depends critically on the implementation and improvement of national Expert Groups; and (d) to protect genetic diversity, the use of local varieties and landraces should not be impeded by organic seed regulations. [ABSTRACT FROM AUTHOR]

There has been a remarkable scientific output on the topic of how climate change is likely to affect plant diseases. This overview addresses the need for review of this burgeoning literature by summarizing opinions of previous reviews and trends in recent studies on the impacts of climate change on plant health. Sudden Oak Death is used as an introductory case study: Californian forests could become even more susceptible to this emerging plant disease, if spring precipitations will be accompanied by warmer temperatures, although climate shifts may also affect the current synchronicity between host cambium activity and pathogen colonization rate. A summary of observed and predicted climate changes, as well as of direct effects of climate change on pathosystems, is provided. Prediction and management of climate change effects on plant health are complicated by indirect effects and the interactions with global change drivers. Uncertainty in models of plant disease development under climate change calls for a diversity of management strategies, from more participatory approaches to interdisciplinary science. Involvement of stakeholders and scientists from outside plant pathology shows the importance of trade-offs, for example in the land-sharing vs. sparing debate. Further research is needed on climate change and plant health in mountain, boreal, Mediterranean and tropical regions, with multiple climate change factors and scenarios (including our responses to it, e.g. the assisted migration of plants), in relation to endophytes, viruses and mycorrhiza, using long-term and large-scale datasets and considering various plant disease control methods. [ABSTRACT FROM AUTHOR]

The level, as well as the structure of private consumption, is influenced by the age structure of the population. This is shown for Austria in the first part of the paper. Age-specific saving rates and consumption patterns on national and regional levels are identified through an analysis of household data of the Austrian consumer budget survey. In a second step, the gained data is used to simulate the future development of the private saving rate and consumption structure in Austria, based on the population projections up to 2050. According to the simulation results, an increase in the private saving rate is to be expected on a national, as well as on a regional level, due to the changing shares of age groups. Furthermore, consumption goods and services in the field of transport will lose significance in favour of expenditures for housing, water, electricity, gas and other fuels, food and non-alcoholic beverages, as well as health products and services. [ABSTRACT FROM AUTHOR]

This paper offers a comparison of government centralization in the United States and in Germany. After briefly laying out the history of federalism in both countries, we identify the instruments of centralization at work. It is argued that an initial constitutional framework of competitive federalism does not prevent the long-term centralization of competencies. Against a background of historical evidence, we discuss the political economics of government centralization. It is argued that formal institutions clearly have an effect on the pathways of government centralization, but not necessarily on the broader trend of centralization. The conclusion is reached that preservation of state and local autonomy may eventually hinge on informal political institutions. [ABSTRACT FROM AUTHOR]

The question concerning when a governmental intervention in the market system is justified has occupied economists from the very beginning and has been a controversial discussion topic for just as long. Against this background, with respect to modern consumer policy, which still represents a relatively young field in the theory of economic policy, it is vital to find sound economic reasons for governmental regulations in order to protect consumers. Therefore, the article attempts to assess what the various economic literatures have added to our understanding of good consumer policy. For this reason, those policy implications that might flow from different theoretical approaches in order to broaden the foundation of an economic justification for consumer policy will be analysed. For this purpose, the consumer policy implications of the Economics of Information will be described, including a denomination of some certain problems all of which are not covered satisfactorily by this approach. Subsequently and in order to amend the informational economics framework, further economical approaches from New Institutional Economics, Behavioural Economics as well as Behavioural Consumer Research, which provide a complementary analysis of consumer behaviour in consideration of the respective decision-making situations and determining constraints (formal and informal rules, cognitive and emotional boundaries), will be discussed comparatively with respect to their consumer policy implications. [ABSTRACT FROM AUTHOR]

Most species of flower-visiting Hymenoptera are trichromatic, with photoreceptor spectral sensitivity peaks in the UV, blue and green regions of the spectrum. Red flowers, therefore, should be relatively difficult to detect for such insects. Nevertheless, in population biological studies in the bumblebee, Bombus terrestris, the Sardinian island population ( B. t. sassaricus) displayed significantly higher responses to red artificial flowers (in tests of innate colour choice and detectability) than several mainland populations of the same species (Chittka et al. in Cognitive ecology of pollination, pp 106–126, ; Popul Ecol 46:243–251, . Since there is relatively little physiological data on population differences in sensory systems, we used intracellular recording to compare photoreceptor spectral sensitivity in B. t. sassaricus and the southern European and Mediterranean population, B. t. dalmatinus. The results show both populations to be UV–blue–green trichromats, but with a small but significant increase in long-wave sensitivity in island bees. Spectral peaks were estimated at 348, 435 and 533 nm ( B. t. dalmatinus) and 347, 436 and 538 nm ( B. t. sassaricus) for UV, blue and green receptors, respectively. There were no significant differences in UV and blue receptor sensitivities. We found no photoreceptors maximally sensitive to red spectral light in the Sardinian population and model calculations indicate that the behavioural population differences in colour responses cannot be directly explained by receptor population differences. [ABSTRACT FROM AUTHOR]

We review the rich literature on behavioural responses of aphids (Hemiptera: Aphididae) to stimuli of different colours. Only in one species there are adequate physiological data on spectral sensitivity to explain behaviour crisply in mechanistic terms. Because of the great interest in aphid responses to coloured targets from an evolutionary, ecological and applied perspective, there is a substantial need to expand these studies to more species of aphids, and to quantify spectral properties of stimuli rigorously. We show that aphid responses to colours, at least for some species, are likely based on a specific colour opponency mechanism, with positive input from the green domain of the spectrum and negative input from the blue and/or UV region. We further demonstrate that the usual yellow preference of aphids encountered in field experiments is not a true colour preference but involves additional brightness effects. We discuss the implications for agriculture and sensory ecology, with special respect to the recent debate on autumn leaf colouration. We illustrate that recent evolutionary theories concerning aphid–tree interactions imply far-reaching assumptions on aphid responses to colours that are not likely to hold. Finally we also discuss the implications for developing and optimising strategies of aphid control and monitoring. [ABSTRACT FROM AUTHOR]

The aphid-vectored Potato virus Y (PVY) is currently seen as an important limiting factor in the production of potatoes in many countries. Using a content-analysis approach, we investigated the German extension literature for recommendations regarding the control of PVY. Media included articles from periodicals addressing farmers and agricultural textbooks published in the last five decades (1955–2004). In the current literature (1995–2004), the clearly dominating strategy was found to be insecticidal control, although this strategy has been subject to some criticism in the scientific literature. Over the last five decades we also found a strongly increasing representation of insecticidal strategies. Furthermore, over this period of time, information diversity, measured as the number of different strategies proposed per article or per textbook, decreased consistently. [ABSTRACT FROM AUTHOR]

Grain legumes produce high-quality protein for food and feed, and potentially contribute to sustainable cropping systems, but they are grown on only 1.5% of European arable land. Low temporal yield stability is one of the reasons held responsible for the low proportion of grain legumes, without sufficient quantitative evidence. The objective of this study was to compare the yield stability of grain legumes with other crop species in a northern European context and accounting for the effects of scale in the analysis and the data. To avoid aggregation biases in the yield data, we used data from long-term field experiments. The experiments included grain legumes (lupin, field pea, and faba bean), other broad-leaved crops, spring, and winter cereals. Experiments were conducted in the UK, Sweden, and Germany. To compare yield stability between grain legumes and other crops, we used a scale-adjusted yield stability indicator that accounts for the yield differences between crops following Taylor's Power Law. Here, we show that temporal yield instability of grain legumes (30%) was higher than that of autumn-sown cereals (19%), but lower than that of other spring-sown broad-leaved crops (35%), and only slightly greater than spring-sown cereals (27%). With the scale-adjusted yield stability indicator, we estimated 21% higher yield stability for grain legumes compared to a standard stability measure. These novel findings demonstrate that grain legume yields are as reliable as those of other spring-sown crops in major production systems of northern Europe, which could influence the current negative perception on grain legume cultivation. Initiatives are still needed to improve the crops agronomy to provide higher and more stable yields in future. [ABSTRACT FROM AUTHOR]

A letter to the editor in response to the article "Measures for measures,"published in "Nature" in the issue 444, of 2006.