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.

A new and integrated approach to evaluate the environmental and ecotoxicological impact of herbicide mixtures: A case study in maize.

An index-based approach for a comprehensive evaluation of the potential risk for active substances and their mixtures to impact the environment was developed. Some of the indices considered already exist (PRISW-1, Priority Index), while others were created ex novo from indicators available on open-source platforms (PESTi, ECOi, AGROi). These indices maybe used for an evaluation before use of pesticides by farmers and advisers. The present approach was initially validated for herbicides in maize crops, but it can readily be applied to other PPPs and crops. PESTi index underline the physical and chemical characteristics as a whole, not considering the impact of other factors such as application rate or period of application. Hence, this index may underestimate the risk associated to a certain chemical. AGROi has a precautionary approach. The risk associated to a specific mixture derives from a combination of intrinsic characteristics of the chemicals, agronomic impacts, regulation restrictions and potential hazard to water compartment. The ECOi index is focused on the ecotoxicological impact against non-target organisms. The helpfulness of this index stands in its ability to easily discriminate the ecotoxicological impact of chemicals using indicators commonly available in literature and without making complex calculations. PRISW-1 Index discriminate active substances according to their risk against three representative non-target organisms. However, due to the intrinsic characteristics of each pesticide, a high PRISW-1 value could not always mean an easy movement of the chemical via runoff waters. The information deriving from Priority index may certainly help public authorities to select chemicals to be detected in water monitoring campaigns. The application of these indices may represent a valid decision tool for public stakeholders in defining agricultural measures to reduce the externalities of pest control.

Natural clay and biopolymer-based nanopesticides to control the environmental spread of a soluble herbicide.

In this work a novel nano-formulation is proposed to control leaching and volatilization of a broadly used herbicide, dicamba. Dicamba is subject to significant leaching in soils, due to its marked solubility, and to significant volatilization and vapor drift, with consequent risks for operators and neighbouring crops. Natural, biocompatible, low-cost materials were employed to control its dispersion in the environment: among four tested candidate carriers, a nanosized natural clay (namely, K10 montmorillonite) was selected to adsorb the pesticide, and carboxymethyl cellulose (CMC), a food-grade biodegradable polymer, was employed as a coating agent. The synthesis approach is based on direct adsorption at ambient temperature and pressure, with a subsequent particle coating to increase suspension stability and control pesticide release. The nano-formulation showed a controlled release when diluted to field-relevant concentrations: in tap water, the uncoated K10 released approximately 45% of the total loaded dicamba, and the percentage reduced to less than 30% with coating. CMC also contributed to significantly reduce dicamba losses due to volatilization from treated soils (e.g., in medium sand, 9.3% of dicamba was lost in 24 h from the commercial product, 15.1% from the uncoated nanoformulation, and only 4.5% from the coated one). Moreover, the coated nanoformulation showed a dramatic decrease in mobility in porous media (when injected in a 11.6 cm sand-packed column, 99.3% of the commercial formulation was eluted, compared to 88.4% of the uncoated nanoformulation and only 24.5% of the coated one). Greenhouse tests indicated that the clay-based nanoformulation does not hinder the dicamba efficacy toward target weeds, even though differences were observed depending on the treated species. Despite the small (lab and greenhouse) scale of the tests, these preliminary results suggest a good efficacy of the proposed nanoformulation in controlling the environmental spreading of dicamba, without hindering efficacy toward target species.

Italian weedy rice-A case of de-domestication?

Weedy rice is a representative of the extensive group of feral weeds that derive from crops, but has returned to the lifestyle of a wild species. These weeds develop either from a hybridization of crops with wild relatives (exoferality), or by mutation of crops to weedy forms (endoferality). Due to the close relation of weed and crop, the methods for weed-targeted containment are limited to date. A deeper understanding of the development of such weeds might help to design more efficient and sustainable approaches for weed management. Weedy rice poses a serious threat to rice yields worldwide. It is widely accepted that weedy rice has originated independently in different regions all over the world. However, details of its evolution have remained elusive. In the current study, we investigated the history of weedy rice in northern Italy, the most important rice-growing area in Europe. Our approach was to analyze genes related to weedy traits (SD1, sh4, Rc) in weedy rice accessions compared to cultivars, and to integrate these results with phenotypic and physiological data, as well as historical information about rice farming in Italy. We arrive at a working model for the timeline of evolution of weedy rice in Italy indicating that both exoferality and endoferality acted as forces driving the development of the diverse weedy rice populations found in the region today. Models of weed evolution can help to predict the direction which weed development might take and to develop new, sustainable methods to control feral weeds.

Ailanthone inhibition data on seed germination and seedling growth of Lepidium sativum L. and Raphanus sativus L.

Ailanthone is a quassinoid from Ailanthus altissima (Mill.) Swingle with allelopathic properties that deserves interest for its potential use as a natural herbicide. Data about seed germination and root and hypocotyl length of two model species (Lepidium sativus L.'Inglese' and Raphanus sativus L.'Tondo Rosso BIO') treated with different concentrations of ailanthone are reported. Data derive from experiments performed in a growth chamber on filter paper, non-sterile urban soil, and a cultivation substrate for horticulture. Part of their elaboration and interpretation can be found in the research article titled "Ailanthone from Ailanthus altissima (Mill.) Swingle as potential natural herbicide" (Demasi et al., 2019).

Direct effects of insecticides on common ragweed-implications for natural enemy exclusion trials.

Experimentally applying pesticides is an important method to assess the efficacy of weed biocontrol agents, but potential direct effects of the chemicals on plant performance are controversial or unknown. We assessed how three broad-spectrum insecticides applied in combination affect the performance of the widely invasive, crop-yield reducing, allergenic common ragweed (Ambrosia artemisiifolia L.) in an insect-free environment. Spraying insecticides had no significant effects on aboveground dry weight, seed and pollen output or pollen allergenicity, and only explained 1-8% of variation in these parameters. Our insecticide treatment can hence be applied to assess biocontrol impact on biomass and reproductive output of common ragweed. As our insecticide treatment delayed senescence, however, other methods of insect exclusion should be preferred when studying common ragweed phenology.

Leaching of S-metolachlor, terbuthylazine, desethyl-terbuthylazine, mesotrione, flufenacet, isoxaflutole, and diketonitrile in field lysimeters as affected by the time elapsed between spraying and first leaching event.

The effect of elapsed time between spraying and first leaching event on the leaching behavior of five herbicides (terbuthylazine, S-metolachlor, mesotrione, flufenacet, and isoxaflutole) and two metabolites (desethyl-terbuthylazine and diketonitrile) was evaluated in a 2011-2012 study in northwest Italy. A battery of 12 lysimeters (8.4 m(2) long with a depth of 1.8 m) were used in the study, each filled with silty-loam soil and treated during pre-emergence with the selected herbicides by applying a mixture of commercial products Lumax (4 L ha(-1)) and Merlin Gold (1 L ha(-1)). During treatment periods, no gravity water was present in lysimeters. Irrigation events capable of producing leaching (40 mm) were conducted on independent groups of three lysimeters on 1 day after treatment (1 DAT), 7 DAT, 14 DAT, and 28 DAT. The series was then repeated 14 days later. Leachate samples were collected a few days after irrigation; compounds were extracted by solid phase extraction and analyzed by high-performance liquid chromatography and gas chromatography-mass spectrometry. Under study conditions, terbuthylazine and S-metolachlor showed the highest leaching potentials. Specifically, S-metolachlor concentrations were always found above 0.25 µg L(-1). Desethyl-terbuthylazine was often detected in leached waters, in most cases at concentrations above 0.1 µg L(-1). Flufenacet leached only when irrigation occurred close to the time of herbicide spraying. Isoxaflutole and mesotrione were not measured (<0.1 µg L(-1)), while diketonitrile was detected in concentrations above 0.1 µg L(-1) on 1 DAT in 2011 only.

Microsatellite markers reveal multiple origins for Italian weedy rice.

Weedy rice (Oryza sativa L.) is one of the major issues of rice cultivation worldwide. In Italy, it infests about 70% of the total rice area. Different Weedy Rice populations can be distinguished based on variable morphological and physiological traits; however, little is known about genetic differentiation and origin of Italian weedy rice populations. The objective of this study was to genetically and morphologically characterize and compare different Italian weedy rice populations selected on the basis of different phenotypes. The main Italian rice territory was divided into 10 geographical areas in which 40 weedy rice populations were collected and grouped according to the awn traits. All the individuals of the populations were morphologically characterized according to plant and seed traits. Genetic characterization was performed using 19 SSR markers on all the collected accessions, and several rice cultivars, including some very old (late 19th century), nowadays are no longer cultivated. ANOVA showed that morphological plant and seed traits were significantly affected by the collection area and awnedness group. The importance of the awn morphology was also reflected in the Bayesian clustering where, despite a relatively low genetic diversity, the clusters displayed different awn types. An UPGMA dendrogram confirmed the clusters detected in STRUCTURE analysis and also revealed a grouping of certain old cultivars with the weedy rice, suggesting a common origin.