The introduction and rapid dispersal of the African flavivirus West Nile virus (WNV) throughout North America, and the high fatality rate due to encephalitis in birds, horses, other wildlife species and humans, has attracted major attention worldwide. Usutu virus, another flavivirus, came to prominence in 2001, when it was identified as the agent responsible for a drop in the bird population in Austria; previously this encephalitic virus was found only in birds and mosquitoes in Africa. Sindbis virus, a pathogenic alphavirus that causes arthritis, is widespread throughout Africa, Europe, Asia and Australia, infecting a range of arthropods and vertebrates and is genetically related to encephalitic viruses in North America. Currently there is no evidence that any of these viruses cause disease in the UK. Here the presence of virus-specific neutralizing antibodies is reported in the sera of resident and migrant birds in the UK, implying that each of these viruses is being introduced to UK birds, possibly by mosquitoes. This is supported by nucleotide sequencing that identified three slightly different sequences of WNV RNA in tissues of magpies and a blackbird. The detection of specific neutralizing antibodies to WNV in birds provides a plausible explanation for the lack of evidence of a decrease in the bird population in the UK compared with North America. The potential health risk posed to humans and animals by these viruses circulating in the UK is discussed.

Summary This study reviews 52 field experiments, mostly from the UK, studying the effects of cultivation techniques, sowing date, crop density and cultivar choice on Alopecurus myosuroides infestations in cereal crops. Where possible, a statistical meta‐analysis has been used to calculate average responses to the various cultural practices and to estimate their variability. In 25 experiments, mouldboard ploughing prior to sowing winter cereals reduced A. myosuroides populations by an average of 69%, compared with non‐inversion tillage. Delaying drilling from September to the end of October decreased weed plant densities by approximately 50%. Sowing wheat in spring achieved an 88% reduction in A. myosuroides plant densities compared with autumn sowing. Increasing winter wheat crop density above 100 plants m−2 had no effect on weed plant numbers, but reduced the number of heads m−2 by 15% for every additional increase in 100 crop plants, up to the highest density tested (350 wheat plants m−2). Choosing more competitive cultivars could decrease A. myosuroides heads m−2 by 22%. With all cultural practices, outcomes were highly variable and effects inconsistent. Farmers are more likely to adopt cultural measures and so reduce their reliance on herbicides, if there were better predictions of likely outcomes at the individual field level.

biologique d'Alopecurus myosuroides dans le but de prevoir la dynamique des populations grainieres. Les valeurs des parametres ont ete obtenues a partir de la bibliographie et d'une simple experimentation de travail du sol en plein champ utilisant des grains en matiere plastique coloree. Dans les simulations, la stabilite de la distribution verticale a ete atteinte aussi rapidement apres un labour qu'apres un travail avec des dents rigides. Les distributions etaient tres differentes pour les deux fa?ons culturales, etant sous forme d'oscillations amorties pour le labour, et d'asymptote pour le travail avec des dents rigides. Summary: Rteume: ZusammenfassungA matrix model was constructed for the prediction of vertical seed movement within the soil. This was inserted into a model of the life-cycle of Alopecurus myosuroides in order to predict seed population dynamics. Parameter values were obtained from published sources and from a single field cultivation experiment using coloured plastic beads. In simulations, stability of vertical distribution was reached sooner under ploughing than under rigid tine cultivation. Stable distributions were very different for the two cultivation methods, being reached by damped oscillations in the case of ploughing and asymptotically in the case of rigid tine cultivation. Un modele pour evaluer les effets des fafons culturales sur la distribution verticale des graines d'adventices dans le solUn modele matriciel a ete etabli pour prevoir le deplacement vertical des graines dans le sol. Celui-ci a ete inclus dans un modele du cycle • Present address:

Won the Weed Science Society of America Annual award for best paperThe intensification of crop management in the U.K. over the past 60 years has resulted in the decline of the Populations of a number of annual plant species adapted to arable habitats. In contrast, other species continue to be common as arable weeds. A Community assembly approach was taken to explain these recent changes in the weed flora using databases of plant functional traits, a pot experiment, and weed surveys OF the Broadbalk long-term experiment. The hypothesis was tested that species that have been selected against by increased fertilizer inputs and herbicide use share an adverse combination of traits. An analysis comparing the combination Of Maximum height, seed weight, and time of first flowering of 29 common and 32 rare or threatened U.K. autumn weeds established that rare or threatened species Occupied an area of trait space that was distinct from the common species. A rare weed trait syndrome of short stature, large seed, and late flowering was identified. The theory that species with a trait syndrome that is Currently unfavorable are better adapted for less fertile environments was Supported by the pot experiment. Species with a combination of short stature and large seed had a relatively greater competitive ability in low compared to high fertility treatments. Analysis of survey data from the Broadbalk long-term experiment confirmed that, as N inputs increased, the abundance of the two functional groups that contained only common species remained stable or increased; whereas, the groups dominated by rare or threatened species declined as fertility increased. An understanding of the response traits of arable plants to management filters, including fertilizer inputs and herbicide, is valuable for designing conservation strategies for rare species or predicting Future shifts in the functional diversity of weed communities including the potential for invasive species to establish

This is the author accepted manuscript. The final version is available from Springer via http://dx.doi.org/10.1007/s13593-016-0350-5Climate change is caused by the release of greenhouse gases in the atmosphere. Climate change will impact many activities, but its effects on agricultural production could be acute. Estimates of annual damages in agriculture due to temperature increase or extended periods of drought will be more costly than damages in other activities. Yield losses are caused both by direct effects of climate change on crops and by indirect effects such as increased inputs in crop production for weed control. One possible solution to counteract the effects of climate change is to seek crop cultivars that are adapted to highly variable, extreme climatic conditions and pest changes. Here we review the effects of climate change on crop cultivars and weeds. Biomass increase will augment marketable yield by 8?70 % for C3 cereals, by 20?144 % for cash and vegetable crops, and by 6?35 % for flowers. Such positive effects could however be reduced by decreasing water and nutrient availability. Rising temperature will decrease yields of temperature-sensitive crops such as maize, soybean, wheat, and cotton or specialty crops such as almonds, grapes, berries, citrus, or stone fruits. Rice, which is expected to yield better under increased CO2, will suffer serious yield losses under high temperatures. Drought stress should decrease the production of tomato, soybean, maize, and cotton. Nevertheless, reviews on C4 photosynthesis response to water stress in interaction with CO2 concentration reveal that elevated CO2 concentration lessens the deleterious effect of drought on plant productivity. C3 weeds respond more strongly than C4 types to CO2 increases through biomass and leaf area increases. The positive response of C3 crops to elevated CO2 may make C4 weeds less competitive for C3 crops, whereas C3 weeds in C4 or C3 crops could become a problem, particularly in tropical regions. Temperature increases will mainly affect the distribution of weeds, particularly C4 type, by expanding their geographical range. This will enhance further yield losses and will affect weed management systems negatively. In addition, the expansion of invasive weed species such as itchgrass, cogongrass, and witchweed facilitated by temperature increases will increase the cost for their control. Under water or nutrient shortage scenarios, an r-strategist with characteristics in the order S-C-R, such as Palmer amaranth, large crabgrass, johnsongrass, and spurges, will most probably prevail. Selection of cultivars that secure high yields under climate change but also by competing weeds is of major importance. Traits related with (a) increased root/shoot ratio, (b) vernalization periods, (c) maturity, (d) regulation of node formation and/or internode distance, (e) harvest index variations, and (f) allelopathy merit further investigation. The cumulative effects of selecting a suitable stress tolerator-competitor cultivar will be reflected in re...

Blackgrass is the most important herbicide-resistant weed in Europe, occurring in 10 countries. Enhanced metabolism is the most common mechanism, conferring partial resistance to a wide range of herbicides, but acetyl-CoA carboxylase (ACCase) target-site resistance also occurs widely. Recently, acetolactate synthase (ALS) target-site resistance conferred by a Pro197 mutation was identified in blackgrass in England and is of concern because of increasing use of sulfonylurea herbicides such as mesosulfuron + iodosulfuron. Resistance management strategies encourage (1) greater use of cultural control measures such as plowing, crop rotation, and delayed drilling; (2) reduced reliance on high-risk herbicides (ACCase, ALS); and (3) use of mixtures and sequences of herbicides with different modes of action. A key message is that, as weeds are relatively immobile, preventing and managing herbicide resistance is largely within the individual farmer's own control. In practice, financial and environmental pressures limit the scope for more cultural control, and the European Community Pesticide Review will result in fewer alternative herbicides being available. Consultants often feel unable to recommend lower risk but weaker herbicide strategies to farmers because the amount of blackgrass remaining might be unacceptable. This dilemma is exemplified by the recent introduction of a formulated mixture of mesosulfuron + iodosulfuron, which has given outstanding control of blackgrass. Farmers expect new herbicides to become available, but this optimistic view appears misplaced. A primary aim is to continue to encourage farmers to integrate cultural and chemical control in a long-term strategy.

Implementation of integrated weed management (IWM) has been poor, with little evidence of concomitant reductions in herbicide use. Non-chemical methods are often adopted as a means of compensating for reduced herbicide efficacy, due to increasing resistance, rather than as alternatives to herbicides. Reluctance to adopt non-chemical methods is not due to a lack of research or technology but to a lack of farmer motivation and action. Justifiably, herbicides are often seen as the easier option -their convenience outweighs the increased complexity, costs and management time associated with non-chemical alternatives. Greater use of non-chemical alternatives to herbicides will only occur if the following seven aspects are addressed: (i) better recognition of the reasons why farmers are reluctant to use non-chemical alternatives; (ii) encouraging farmers to adopt a longer-term approach to weed control; (iii) changing farmers' attitudes to pesticides; (iv) paying more attention to the individual farmer's perspective; (v). greater involvement of economists, social scientists and marketing professionals; (vi) re-evaluating research and extension priorities; and (vii) changing the mindset of funders of research and extension. If 'persuasion' fails to deliver greater implementation of IWM, authorities may resort to greater use of financial and other incentives combined with tougher regulations.

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