The utility of the 'Arable Weeds and Management in Europe' database: Challenges and opportunities of combining weed survey data at a European scale.

Over the last 30 years, many studies have surveyed weed vegetation on arable land. The 'Arable Weeds and Management in Europe' (AWME) database is a collection of 36 of these surveys and the associated management data. Here, we review the challenges associated with combining disparate datasets and explore some of the opportunities for future research that present themselves thanks to the AWME database. We present three case studies repeating previously published national scale analyses with data from a larger spatial extent. The case studies, originally done in France, Germany and the UK, explore various aspects of weed ecology (community composition, management and environmental effects and within-field distributions) and use a range of statistical techniques (canonical correspondence analysis, redundancy analysis and generalised linear mixed models) to demonstrate the utility and versatility of the AWME database. We demonstrate that (i) the standardisation of abundance data to a common measure, before the analysis of the combined dataset, has little impact on the outcome of the analyses, (ii) the increased extent of environmental or management gradients allows for greater confidence in conclusions and (iii) the main conclusions of analyses done at different spatial scales remain consistent. These case studies demonstrate the utility of a Europe-wide weed survey database, for clarifying or extending results obtained from studies at smaller scales. This Europe-wide data collection offers many more opportunities for analysis that could not be addressed in smaller datasets; including questions about the effects of climate change, macro-ecological and biogeographical issues related to weed diversity as well as the dominance or rarity of specific weeds in Europe.

Farmers' perspective on herbicide-resistant weeds and application of resistance management strategies: results from a German survey.

BACKGROUND: A herbicide resistance survey was conducted in Germany to determine farmers' awareness of herbicide resistance and experience with resistant weeds, the information sources on herbicide resistance used and the methods employed to confirm resistance. In addition, the application pattern and perception of resistance management strategies by farmers were assessed. RESULTS: The majority of farmers (88%) were aware of the presence of herbicide resistance cases in Germany and 64% and 50% of farmers reported that resistant weeds had been detected in their county and on their farm, respectively. Resistance management strategies were reported to be applied by 87% of the farmers and three clusters of different resistance management approaches used to minimize the evolution of resistant weed populations were identified and linked to farmers' perception of resistance and farm management characteristics. When asked about obstacles to adopting resistance management strategies, higher cost was the obstacle most cited by farmers, followed by weather and labour intensity/labour costs. CONCLUSION: Outcomes from this survey may help researchers and crop consultants to increase understanding of farmers' perception of herbicide resistance issues, to improve knowledge dissemination concerning herbicide resistance and to develop resistance management programmes with high agronomic practicability and acceptance by farmers. © 2017 Society of Chemical Industry.

Resistance risk assessment within herbicide authorisation--a call for sensitivity data.

In most European countries, the risk of herbicide resistance is assessed as part of the authorisation of herbicides in accordance with EPPO Standard PP 1/213(2). Because the susceptibility of weed populations to a certain herbicide may vary greatly, one part of resistance risk assessment is the testing for sensitivity variation among different populations of target weed species with a high resistance risk. This paper emphasises the importance of sensitivity data provision with regard to the recent EU Regulation (EC) 1107/2009 concerning the placing of plant protection products on the market and outlines the main technical requirements for sensitivity data. A useful principle is that sensitivity data should be provided for all herbicides with a high resistance risk regardless of whether resistance has already evolved against the herbicidal substance. Methodical details regarding the generation of sensitivity data are discussed, together with remaining questions that will need to be addressed if a harmonised assessment of herbicide resistance risk is to be achieved.