Transdisciplinary weed research: new leverage on challenging weed problems?

Transdisciplinary weed research (TWR) is a promising path to more effective management of challenging weed problems. We define TWR as an integrated process of inquiry and action that addresses complex weed problems in the context of broader efforts to improve economic, environmental and social aspects of ecosystem sustainability. TWR seeks to integrate scholarly and practical knowledge across many stakeholder groups (e.g. scientists, private sector, farmers and extension officers) and levels (e.g. local, regional and landscape). Furthermore, TWR features democratic and iterative processes of decision‐making and collective action that aims to align the interests, viewpoints and agendas of a wide range of stakeholders. The fundamental rationale for TWR is that many challenging weed problems (e.g. herbicide resistance or extensive plant invasions in natural areas) are better addressed systemically, as a part of broad‐based efforts to advance ecosystem sustainability, rather than as isolated problems. Addressing challenging weed problems systemically can offer important new leverage on such problems, by creating new opportunities to manage their root causes and by improving complementarity between weed management and other activities. While promising, this approach is complicated by the multidimensional, multilevel, diversely defined and unpredictable nature of ecosystem sustainability. In practice, TWR can be undertaken as a cyclic process of (i) initial problem formulation, (ii) ‘broadening’ of the problem formulation and recruitment of stakeholder participants, (iii) deliberation, negotiation and design of an action agenda for systemic change, (iv) implementation action, (v) monitoring and assessment of outcomes and (vi) reformulation of the problem situation and renegotiation of further actions. Notably, ‘purposive’ disciplines (design, humanities and arts) have central, critical and recurrent roles in this process, as do integrative analyses of relevant multidimensional and multilevel factors, via multiple natural and social science disciplines. We exemplify this process in prospect and retrospect. Importantly TWR is not a replacement for current weed research; rather, the intent is to powerfully leverage current efforts.     

Farmers’ attitudes towards pesticide labels: implications for personal and environmental safety

The label of pesticide containers is a major source of information for the use of pesticides, but research on whether farmers use this information is scarce. A survey of small-scale cotton farmers was conducted in the area of Punjab, Pakistan, to study attitudes related with the use of pesticide labels. The majority of the farmers (97%) stated that they were using pesticide products purchased in their original containers and accompanied by written information for use. However, 73% of the farmers reported that they usually do not read this information. Elderly, less educated, and experienced farmers in chemical pest control, but without previous training, were found to be less likely to read the labels. A large part of the farmers (34%) stated that they primarily rely on information of pesticide retailers for pesticide use, while nearly four out of ten said they usually rely on other sources of information or their own experience with pesticides. A sizeable proportion of the farmers (9%) mentioned that there is no need to receive information on such issues. Effective pesticide risk communication conveyed through label information is important so that potential risks from pesticide handling may be mitigated at the point of use.     

Natural products: a strategic lead generation approach in crop protection discovery

With the anticipated population growth in the coming decades, the changing regulatory environment, and the continued emergence of resistance to commercial pesticides, there is a constant need to discover new lead chemistries with novel modes of action. We have established a portfolio of approaches to accelerate lead generation. One of these approaches capitalizes on the rich bioactivity of natural products (NPs), highlighted by the numerous examples of NP‐based crop protection compounds. Within Corteva Agriscience and the affiliated preceding companies, NPs have been a fruitful approach, for nearly three decades, to identifying and bringing to the market crop protection products inspired by or originating from NPs, . Included in these NP‐based crop protection products are the spinosyns family of insecticides, and those from more recent areas of NP‐based fungicidal chemistry, as highlighted in this perspective. © 2019 Society of Chemical Industry     

Evaluation of models to predict take-all incidence in winter wheat as a function of cropping practices,soil, and climate

The incidence and severity of take-all, caused by Gaeumannomyces graminis var. tritici (Ggt), in susceptible crops depend on climate, soil characteristics and cropping practices. Take-all can be controlled by modifying crop rotation, crop management and fungicide treatment. When available, fungicides are used as a seed treatment and are partially effective. There is currently no reliable method for helping farmers to optimise their choice of cropping system to improve take-all control. In this study, we defined 16 models, based on various mathematical functions and input variables, for predicting disease incidence in a wheat crop as a function of soil characteristics, climate, crop rotation and crop management. The parameters of these models were estimated from field experiments carried out at six sites in the north of France over a ten-year period. The root mean squared error of prediction (RMSEP) values of the models were estimated by cross validation and compared. RMSEP was in the range 16.34–65.93% and was higher for the models based on multiplicative functions. The lowest RMSEP value was obtained for a dynamic model simulating disease incidence during the crop cycle and which included among input variables the percentage of diseased plants determined at GS30.     

Reduced herbicide doses in field crops: A review

Farmers are becoming increasingly interested in more comprehensive weed management programs that reduce weed populations over time and in the use of reduced herbicide doses that lower their production costs. Research indicates that there is good potential to reduce the number of herbicide applications and utilize lower herbicide doses within competitive cropping systems. Diverse crop rotations, competitive cultivars, higher crop seed rates, reduced row spacing, specific fertilizer placement, and cover crops have been identified as integral components of competitive cropping systems. This review paper explores the potential for successful use of reduced herbicide doses within competitive cropping systems that have a multiyear approach to weed management. The utilization of decision support systems or new methods of assessing active weed growth are discussed in light of further enhancing the successful use of reduced herbicide doses and advising farmers on when (and when not) they might be a viable option.     

Decision support systems: barriers and farmers’ need for support*

The highly complex knowledge of scientific disciplines makes nuanced analysis and modelling possible. However, the information produced often does not reach farmers because it is presented in a way that does not correspond to the way their work is carried out in practice. The decision support system Crop Protection Online is widely used by advisors and as a learning tool for students. Although the system has been validated in many field trials over the years and has shown reliable results, the number of end‐users among farmers has been relatively low during the last 10 years (approximately 1000 farmers). A sociological investigation of farmers’ decision‐making styles in the area of crop protection has shown that arable farmers can be divided into three major groups: (a) system‐orientated farmers, (b) experience‐based farmers and (c) advisory‐orientated farmers. The information required by these three groups to make their decisions varies and therefore different ways of using decision support systems need to be provided. Decision support systems need to be developed in close dialogue and collaboration with user groups.     

A mixed methodology framework for the assessment of the Voluntary Initiative

The Voluntary Initiative (VI) is a UK programme of measures aimed at reducing the adverse effects of pesticides on the environment. It was initiated in 2001 and will be evaluated during 2006 following a five-year trial period. To assess such a complex scheme, a mixed methodology approach is appropriate, encompassing the assessment of objective deliverables and issues raised by the farming community. A series of focus groups examined the perceptions of the VI by the farming community. Farmer attitudes to the VI appeared to be influenced by the belief that the UK government will, eventually, introduce some form of pesticide tax regardless of the outcome of the VI. Most farmers expressed that they already followed the principles of the VI. It was also evident that the scheme may become more acceptable and better understood as it becomes incorporated into existing farm assurance schemes. This paper proposes a framework for evaluation of the VI that takes into account these perceptions of the VI by the farming community. Based on the analysis of available data, key questions are identified that should be addressed within the final evaluation. These key questions cover the general themes of completion of VI targets and projects, uptake of the VI, environmental impact of the VI and economic implications. To answer the questions, four methods are proposed: a review of literature, a survey of farmers, questions to agencies and environmental modelling.     

Perspectives on transgenic,herbicide‐resistant crops in the United States almost 20 years after introduction

Herbicide‐resistant crops have had a profound impact on weed management. Most of the impact has been by glyphosate‐resistant maize, cotton, soybean and canola. Significant economic savings, yield increases and more efficacious and simplified weed management have resulted in widespread adoption of the technology. Initially, glyphosate‐resistant crops enabled significantly reduced tillage and reduced the environmental impact of weed management. Continuous use of glyphosate with glyphosate‐resistant crops over broad areas facilitated the evolution of glyphosate‐resistant weeds, which have resulted in increases in the use of tillage and other herbicides with glyphosate, reducing some of the initial environmental benefits of glyphosate‐resistant crops. Transgenic crops with resistance to auxinic herbicides, as well as to herbicides that inhibit acetolactate synthase, acetyl‐CoA carboxylase and hydroxyphenylpyruvate dioxygenase, stacked with glyphosate and/or glufosinate resistance, will become available in the next few years. These technologies will provide additional weed management options for farmers, but will not have all of the positive effects (reduced cost, simplified weed management, lowered environmental impact and reduced tillage) that glyphosate‐resistant crops had initially. In the more distant future, other herbicide‐resistant crops (including non‐transgenic ones), herbicides with new modes of action and technologies that are currently in their infancy (e.g. bioherbicides, sprayable herbicidal RNAi and/or robotic weeding) may affect the role of transgenic, herbicide‐resistant crops in weed management. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.     

The Potential Use of Herbicides in Tropical Peasant Agriculture

Abstract

The possible effects of herbicide use by peasant farmers are examined. It is considered that herbicides could be used for bush clearing but that their use should not be encouraged at present. It is concluded that herbicides can be used to control perennial weeds, to protect cereal crops from witchweed and to reduce the seasonal peak of labour demand.     

The current status of pesticide resistance in Australian populations of the redlegged earth mite (Halotydeus destructor)

BACKGROUND: The redlegged earth mite, Halotydeus destructor Tucker, is an important pest of broad‐acre farming systems in Australia, New Zealand and South Africa. In 2006, high levels of resistance to synthetic pyrethroids were discovered in this species in Western Australia. RESULTS: Between 2007 and 2010, the authors monitored resistance in field populations and found it had spread considerably within the state of Western Australia. Twenty‐six paddocks from 15 individual properties were identified with resistance, and these paddocks ranged over 480 km. To date, resistance has not been detected in any other Australian state. Resistance in H. destructor appears to be found across the entire pyrethroid group, but not to other chemical classes such as organophosphates and carbamates, or other chemistries with novel modes of action. CONCLUSION: The high levels of resistance occurring in Western Australia have caused considerable economic losses due to ineffective chemical applications and mortality of crop plants at seedling establishment. These findings highlight the need for a comprehensive resistance surveillance programme to be developed for H. destructor within Australia. Growers need to consider non‐chemical approaches for pest control and should be encouraged to implement pesticide resistance management programmes for H. destructor. Copyright © 2011 Society of Chemical Industry     

Basic substances: an opportunity for approval of low‐concern substances under EU pesticide regulation

Plant extracts and byproducts furnish various alternative products for crop protection and are traditionally used by farmers. However, the cost and timeframe for their registration as active substances are prohibitive for small companies and farmers' associations with the new Plant Protection Products (PPP) Regulation (EC) No. 1107/2009. However, there is now a possibility of registering light compounds as ‘basic substances’, a new category described in Article 23 and in ‘Whereas/Recital 18’. We developed a regulatory expertise on the approval of such products within the framework of the PPP regulation. A Draft Assessment Report in one volume was established, later transformed by EC Directorate into a Basic Substance Application Template, and subsequently used by the EC as a matrix for the corresponding Guidelines for applicants (SANCO 10363/2012 rev. 9). Here we provide further tools, consisting of methodological, linguistic and strategic recommendations in order to constitute a Basic Substance Application (BSA) and proceed to its registration. While the use of alternative agents for crop protection is increasing both in organic and conventional agriculture, these usages are still considered as ‘minor uses’. Our approach and tools are valuable to non‐PPP specialised applicants for simplifying and facilitating their submission of the BSA. © 2015 Society of Chemical Industry     

Developing Integrated Disease Management Strategies Against Non-persistently Aphid-borne Viruses: A Model Programme

There is a need to develop integrated disease management strategies that are comprehensive and can protect farmers from the economic hardship that arises when epidemics of non-persistently aphid-borne viruses damage their crops. The aim of this review is to provide a model for future programmes to use when developing such strategies for different combinations of non-persistently aphid-borne viruses and crops. The model programme described is a 15-year study to develop integrated management strategies against two non-persistently aphid-borne viruses causing damaging diseases of lupins and to get them adopted by farmers. The success of the programme depended on an interdisciplinary team approach, obtaining a detailed understanding of the factors favouring virus epidemics, field evaluation for virus resistance, and field experiments that determined the effectiveness of individual control measures. The strategies developed were designed to cause few additional labour demands, and minimal disruption to normal farming operations or extra expense.The programme devised integrated management strategies for the diseases caused by Cucumber mosaic virus (CMV) and Bean yellow mosaic virus (BYMV) in crops of narrow-leafed lupin (Lupinus angustifolius) under the conditions of low-input, dryland agriculture in the south-west Australian grainbelt, which has a Mediterranean-type climate. CMV is introduced into lupin crops by sowing virus-infected lupin seed while aphids spread BYMV into the growing crop from adjacent virus-infected, clover-based pastures. Grain yield losses are substantial when virus spread by aphids is sufficient to cause high incidences of infection within crops. The management strategies were gradually improved and expanded as understanding of the epidemiology of viruses in lupins improved and the results of field experiments involving potential control measures became available. The individual measures combined within the integrated management strategy for each virus were: sowing seed stocks with minimal virus contents, sowing cultivars with inherently low seed transmission rates and isolation from neighbouring lupin crops (CMV only); perimeter non-host barriers and avoiding fields with large perimeter : area ratios (BYMV only); nobreak promoting early canopy development, generating high plant densities, adjusting row spacing, direct drilling into retained stubble, sowing early maturing cultivars, maximising weed control and crop rotation (both viruses). Recommendations to apply insecticide were included solely for spraying high value seed crops (CMV only) or virus-infected pastures next to crops (BYMV only). The justification for selection of each individual control measure, its mode of action in either removing or minimising the virus infection source or suppressing virus spread by aphids and the extent to which it has been adopted by farmers is described. The approach used to transfer the strategies to farmers and the need to avoid complacency following the overall success of the work is emphasised. An integrated disease management strategy developed to clean up the lupin breeding programme from seed-borne virus infection and prevent release of infected seed stocks of new cultivars is also described. It can serve as an example of what is needed to tackle seed-borne virus contamination in other plant breeding or selection programmes.     

Assessment of leaf cover and crop soil cover in weed harrowing research using digital images

Objective assessment of crop soil cover, defined as the percentage of leaf cover that has been buried in soil because of weed harrowing, is crucial to further progress in post‐emergence weed harrowing research. Up to now, crop soil cover has been assessed by visual scores, which are biased and context‐dependent. The aim of this study was to investigate whether digital image analysis is a feasible method to estimate crop soil cover in the early growth stages of cereals. Two main questions were examined: (i) how to capture suitable digital images under field conditions with a standard high‐resolution digital camera and (ii) how to analyse the images with an automated digital image analysis procedure. The importance of light conditions, camera angle, size of recorded area, growth stage and direction of harrowing were investigated, in order to establish a standard for image capture and an automated image analysis procedure based on the excess green colour index was developed. The study shows that the automated digital image analysis procedure provided reliable estimations of leaf cover, defined as the proportion of pixels in digital images determined to be green, which were used to estimate crop soil cover. A standard for image capture is suggested and it is recommended that digital image analysis be used to estimate crop soil cover in future research. The prospects of using digital image analysis in future weed harrowing research are discussed.     

Dung‐inhabiting fungi: a potential reservoir of novel secondary metabolites for the control of plant pathogens

Coprophilous fungi are a large group of saprotrophic fungi mostly found in herbivore dung. The number of these fungi undergoing investigation is continually increasing, and new species and genera continue to be described. Dung‐inhabiting fungi play an important ecological role in decomposing and recycling nutrients from animal dung. They produce a large array of bioactive secondary metabolites and have a potent enzymatic arsenal able to utilise even complex molecules. Bioactive secondary metabolites are actively involved in interaction with and defence against other organisms whose growth can be inhibited, resulting in an enhanced ecological fitness of producer strains. Currently, these antibiotics and bioactive secondary metabolites are of interest in medicine in particular, while very little information is available concerning their potential use in agriculture. This review introduces the ecology of dung‐inhabiting fungi, with particular emphasis on the production of antibiotic compounds as a means to compete with other microorganisms. Owing to the fast pace of technological progress, new approaches to predicting the biosynthesis of bioactive metabolites are proposed. Coprophilous fungi should be considered as elite candidate organisms for the discovery of novel antifungal compounds, above all in view of their exploitation for crop protection. © 2015 Society of Chemical Industry     

Do plant trichomes cause more harm than good to predatory insects?

Plants use trichomes as a morphological defense against attacks from herbivores. The literature was reviewed to test the hypothesis that trichome‐bearing (pubescent) plants do not cause more harm than good to predators. Forty seven records on interactions between plant trichomes and predatory insects were found. Overall, the records reveal that trichomes have more harmful than beneficial effects on predators. Fortunately, most harmful effects are sublethal; they usually affect movement, development, oviposition and predation potential. In worst cases, sticky exudates from glandular trichomes entrap predators. The hooked tips on non‐glandular trichomes impale predators. Entrapped and impaled predators often die from desiccation or starvation. Plant cultivars with high (rather than low) trichome density cause the most harm, and trichomes on tomato and some beans often cause more harm than good to predatory beetles, true bugs and lacewings. Whether these harmful effects have a net negative effect on plant fitness is poorly known and ripe for study. When developing and testing cultivars with increased trichome‐based resistance to herbivory, the question as to whether these technologies are compatible with the functional role of those predators (single or combined species) capable of suppressing herbivore populations should be considered. Published 2014. This article is a U.S. Government work and is in the public domain in the USA     

Mass spectrometric techniques as aids in the diagnosis of gangrene in potatoes caused by Phoma exigua var. foveata

Current diagnosis of gangrene in potato tubers, caused byPhoma exigua var.foveata, is based on isolation and identification of the causal organism or on thin-layer chromatographic (TLC) detection of the anthraquinone pigment pachybasin (1-hydroxy-3-methylanthraquinone). In this paper alternative diagnostic approaches are described based on detection of specific ions by pyrolysis mass spectrometry (Py-MS), direct probe mass spectrometry (DIP-MS) and gas chromatography-mass spectrometry (GC-MS). The advantages and disadvantages of these methods are discussed in comparison with the TLC approach. GC-MS is a promising technique because of its high specificity, sensitivity and suitability for automation. Moreover, the MS approaches may lead to a reduction of total expertise time.Samenvatting De huidige diagnostiek van gangreen in aardappelknollen, veroorzaakt doorPhoma exigua var.foveata, is gebasserd op de isolatie en identifikatie van de schimmel of op de dunnelaag-chromatografische (TLC) bepaling van het pigment pachybasine (1-hydroxy-3-methylanthrachinon).In dit artikel worden nieuwe diagnostische benaderingen beschreven die gebaseerd zijn op de detectie van specifieke ionen door middel van pyrolyse-massaspectrometrie (Py-MS), direct-probe-massaspectrometrie (DIP-MS) en gaschromatografie-massaspectrometrie (GC-MS). De voor- en nadelen van deze methoden worden behandeld en vergeleken met de dunnelaag-chromatografische methode.GC-MS is een veelbelovende methode vanwege de grote specificiteit, gevoeligheid en geschiktheid voor automatisering. Op den duur kunnen de MS-methoden leiden tot een verkorting van de totale expertisetijd.     

Comparison of crop and weed height,for potential differentiation of weed patches at harvest

Weeds and weed control are major production costs in global agriculture, with increasing challenges associated with herbicide‐based management because of concerns with chemical residue and herbicide resistance. Non‐chemical weed management may address these challenges but requires the ability to differentiate weeds from crops. Harvest is an ideal opportunity for the differentiation of weeds that grow taller than the crop, however, the ability to differentiate late‐season weeds from the crop is unknown. Weed mapping enables farmers to locate weed patches, evaluate the success of previous weed management strategies, and assist with planning for future herbicide applications. The aim of this study was to determine whether weed patches could be differentiated from the crop plants, based on height differences. Field surveys were carried out before crop harvest in 2018 and 2019, where a total of 86 and 105 weedy patches were manually assessed respectively. The results of this study demonstrated that across the 191 assessed weedy patches, in 97% of patches with Avena fatua (wild oat) plants, 86% with Raphanus raphanistrum (wild radish) plants and 92% with Sonchus oleraceus L. (sow thistles) plants it was possible to distinguish the weeds taller than the 95% of the crop plants. Future work should be dedicated to the assessment of the ability of remote sensing methods such as Light Detection and Ranging to detect and map late‐season weed species based on the results from this study on crop and weed height differences.     

Diversity and pathogenicity of the Ceratocystidaceae associated with cacao agroforests in Cameroon

Knowledge of the diversity and ecology of plant pathogenic fungi in cacao agroforests and surrounding natural ecosystems can inform the development of sustainable management strategies for new cacao disease outbreaks. This study investigated the occurrence of fungi related to the Ceratocystidaceae and their nitidulid beetle vectors in cacao agroforests in Cameroon, under diverse agroecological conditions. The fungi and their vectors were collected from artificially induced stem wounds on cacao and associated shade trees. Collections were also made from abandoned cacao pod husks and other tree wounds within and around plantations. Fungal isolates were identified using DNA sequence‐based phylogenies and morphological comparisons, and two representatives of each species were evaluated for pathogenicity on cacao. Five species of Ceratocystidaceae were recovered, including Huntiella chlamydoformis sp. nov., H. pycnanthi sp. nov. and H. moniliformis, as well as Thielaviopsis cerberus and T. ethacetica. The incidence of these fungi appeared to be influenced by the prevailing agroecological conditions. Nitidulid beetles in the genus Brachypeplus were found to be their most common insect associates on cacao. Both T. ethacetica and H. pycnanthi produced extensive lesions after inoculation on branches of mature cacao trees, while T. ethacetica also caused pod rot. Although their impact remains unknown, fungi in the Ceratocystidaceae and their nitidulid beetle vectors are common and probably contribute to the parasitic pressure in Cameroonian cacao agrosystems.     

Practical experiences with a system for site-specific weed control in arable crops using real-time image analysis and GPS-controlled patch spraying

Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Primarily, spatial information allows a potential reduction in herbicide use, when post‐emergent herbicides are only applied to field sections with high weed infestation levels. This paper presents a system for site‐specific weed control in sugar beet, maize, winter wheat, winter barley, winter rape and spring barley. The system includes on‐line weed detection using digital image analysis, computer‐based decision making and Global Positioning System‐controlled patch spraying. In a 2‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 6–81% for herbicides against broad leaved weeds and 20–79% for grass weed herbicides. Highest savings were achieved in cereals followed by sugar beet, maize and winter rape. The efficacy of weed control varied from 85% to 98%, indicating that site‐specific weed management will not result in higher infestation levels in the following crops.     

基于多主体的传统村落文化遗产保护传承感知及提升模式

许多传统村落文化遗产面临着被破坏与消亡的威胁。文中以9个北京市首批市级传统村落为案例地,采用指标体系法、熵权法,分析村委会、村民、游客对传统村落文化遗产保护传承的感知评价。结果表明:1)村委会对文化遗产保护状况满意度较高,但非物质文化遗产缺乏良好的传承机制,文化遗产保护传承投入较低,旅游开发正逐步成为传统村落文化遗产保护传承和利用的重要途径。2)村民对非物质文化遗产的认同度较低,他们对文化遗产保护传承现状的满意度并不高,特别是其保护感知度偏低、参与度有限。3)游客对于传统村落非物质文化遗产保护传承现状满意度较高,其保护感知度逐渐上升。4)案例村落文化遗产保护传承度均处于较低水平,具有较大的提升空间。最后,从内容内涵、途径方式、参与主体、最终目标四个方面构建了传统村落文化遗产保护传承提升模式。