Modeling the Main Fungal Diseases of Winter Wheat: Constraints and Possible Solutions

The first step in the formulation of disease management strategy for any cropping system is to identify the most important risk factors. This is facilitated by basic epidemiological studies of pathogen life cycles, and an understanding of the way in which weather and cropping factors affect the quantity of initial inoculum and the rate at which the epidemic develops. Weather conditions are important factors in the development of fungal diseases in winter wheat, and constitute the main inputs of the decision support systems used to forecast disease and thus determine the timing for efficacious fungicide application. Crop protection often relies on preventive fungicide applications. Considering the slim cost−revenue ratio for winter wheat and the negative environmental impacts of fungicide overuse, necessity for applying only sprays that are critical for disease control becomes paramount for a sustainable and environmentally friendly crop production. Thus, fungicides should only be applied at critical stages for disease development, and only after the pathogen has been correctly identified. This chapter provides an overview of different weather-based disease models developed for assessing the real-time risk of epidemic development of the major fungal diseases (Septoria leaf blotch, leaf rusts and Fusarium head blight) of winter wheat in Luxembourg

Effects of regional climate change on brown rust disease in winter wheat

Projected climate changes will affect wheat crop production both in the main processes of plant growth and development but also in the occurrences and severities of plant diseases. We assessed the potential infection periods of wheat leaf rust (WLR) at two climatologically different sites in Luxembourg. A threshold-based model, taking hourly values of air temperatures, relative humidity and precipitation during night-time into account, was used for calculating favourable WLR infection days during three periods throughout the cropping season. Field experiments were conducted during the 2003–2013 period at the selected sites. Projected climate data, from a multi model ensemble of regional climate models (spatial resolution 25 km) as well as an additional projection with a higher spatial resolution of 1.3 km, were used for investigating the potential WLR infection periods for two future time spans. Results showed that the infections of WLR were satisfactorily simulated during the development of wheat at both sites for the 2003–2013 period. The probabilities of WLR detection were close to 1 and the critical success index ranged from 0.80 to 0.94 (perfect score = 1 for both). Moreover, the highest proportions of favourable days of WLR infection were simulated during spring and summer at both sites. Regional climate projections showed an increase in temperatures by 1.6 K for 2041–2050 and by 3.7 K for 2091–2100 compared to the reference period 1991–2000. Positive trends in favourable WLR infection conditions occur at both sites more conducive than in the reference period due to projected climatic conditions

Performance of leaf wetness sensor used in winter wheat disease management

Wetness on crop leaves has particular epidemiological significance because many fungal diseases affect plants only when free moisture is present on leaves. The leaf wetness sensor detects the presence of wetness on a leaf’s surface, enabling researchers and producers to forecast disease and protect plant canopies, and consequently to optimize fungicide application and often reduce environmental load. This research project aimed at better understanding the leaf wetness duration and its influence in winter wheat disease. Measurement of surface wetness duration by three electronic flat-plate sensors (Model 237-Campbell Scientific, Inc) in wheat fields were compared with tactile and visual observations in replicated field experiments at the site of Arlon (Belgium) during the period May-July 2006 and April-July 2007. Performances of the sensor were evaluated against SWEB model outputs and visual observations of disease symptoms. On the field, dew-onset and dry-off of wetness on leaves were observed visually (with a flash light for dew-onset) at 15-minute intervals. Each sensor was placed close the flag leaf. For the three sensors, the two dew-onset and dry-off times measured in both 2006 and 2007 crop seasons gave a leaf wetness duration (LWD) which was on average one hour less than visual observations. In order to establish a relationship between the surface wetness periods and wheat foliar diseases, LWD was compared with the Septoria leaf blotch (SLB) development risk (main winter wheat disease). A minimal surface wetness duration favourable to infection for SLB was established.Weather-radar data ; Rainfall ; Septoria tritici ; Forecasting system ; Winter wheat ; Epidemiological model ; Surface wetness duration ; Spatializatio

Cinétique de décroissance de la surface verte et estimation du rendement du blé d'hiver

Estimating winter wheat yield through the decreasing phase of its green area. A large number of agrometeorological models for crop yield assessment are available with various levels of complexity and empiricism. However, the current development of models for wheat yield forecasting does not always reflect the inclusion of the loss of valuable green area and its relation to biotic and abiotic processes in production situation. In this study the senescence phase of winter wheat (Triticum aestivum L.) is monitored through the GAI (Green Area Index), calculated from digital hemispherical photographies taken over plots in Belgium, Grand-Duchy of Luxembourg and France. Two curve-fitting functions (modified Gompertz and modified logistic) are used to describe the senescence phase. Metrics derived from these functions and characterizing this phase (i.e. the maximum value of GAI, the senescence rate and the time taken to reach either 37% or 50% of the green surface in the senescent phase) are related to final grain yields. The regression-based models calculated with these metrics showed that final yield could be estimated with a coefficient of determination of 0.83 and a RMSE of 0.48 t·ha-1. Such simple models may be considered as a first yield estimates that may be performed in order to provide a better integrated yield assessment in operational systems. Indeed, estimation of cereal-crop production, particularly wheat, is considered as a priority in most crop research programs due to the relevance of food grain to world agricultural production

Rouille brune du blé, un modèle pour évaluer les risques

peer reviewedL’article présente un outil de prévision de la rouille brune au G.-D. de Luxembourg. De 2000 à 2003, cette maladie apparaissait à la fin de l’épiaison, mais depuis 2003, elle apparaît de plus en plus tôt (GS45 stade gonflement). Cette apparition précoce est probablement liée à des températures printanières supérieures par rapport à la normale 1971-2000. Une analyse des données météorologiques nocturnes et des données d’observation de la maladie sur quatre sites expérimentaux (Everlange, Christnach, Burmerange et Reuler) entre 2000 et 2003 a révélé une forte corrélation positive entre la prédiction de la maladie basée sur le critère d’au moins 12 heures consécutives avec une température comprise entre 8 et 16°C et une humidité supérieure à 60% et la maladie observée sur la F1 (R = 0.93 ; P < 0.05) et sur la F2 (R = 0.87 ; P < 0.05). Les sorties de ce modèle qui a été développé sur base d’une approche stochastique ont été utilisées dans les bulletins d’avertissements diffusés conjointement par le Centre de Recherche Public – Gabriel Lippmann et l’Université de Liège-Campus d’Arlon à partir de 2004. La mise en application de ce modèle a montré un taux de réussite oscillant entre 80 et 85% pour la simulation de la rouille brune au G.-D. de Luxembourg. L’effort se poursuit pour spatialiser les sorties du modèle sur tout le territoire luxembourgeois et faciliter son utilisation par tous les vulgarisateurs agricoles

Approche entrepreneuriale islamique : Singularité et intersections avec les approches entrepreneuriales coutumières

This theoretical publication, resulting from a constructive epistemological posture research using a qualitative study approached in a double sense: By the first qualitative sense relating to the theoretical component: the aim is to develop concepts that will help us better understand customary and Islamic approaches, in entrepreneurial contexts; and by the second qualitative sense relating to the empirical aspect: According to Eisenhardt (1989), for whom, a qualitative approach is necessary and useful when the phenomenon is not sufficiently known and the objective of research is to build rather than test. Notably, entrepreneurship in an Islamic approach, as we discuss in a forthcoming publication, is only presented by a few studies; this sense presents a point of junction with the constructive approach attempting to build an effective entrepreneurial model in an Islamic approach M.E.E.A.I. The objective of this theoretical article is to make a comparison between the practices of the Islamic entrepreneurial approach and its same practices among customary approaches to identify the points that reconcile the two categories of approaches. Then, we accentuate the distinctive aspect of the Islamic approach. The Islamic approach, continued for more than 15 centuries to hold its place in the business world; while preserving the same sources of its legislation 'these sources, and to take into consideration the sphere in which they are applied, have been readjusted and revised through Islamic jurisprudence without departing from the framework of the Shari’a Islamic. Other customary approaches have had to go through centuries to come close to this Islamic approach, in terms of socially responsible entrepreneurship, female entrepreneurship, and the setting up of institutions that ensure the proper functioning of entrepreneurship. &nbsp; &nbsp; JEL Classification: B59 Paper type: Theoretical ResearchCe manuscrit théorique est un complément d’un travail de recherche de posture épistémologique constructive, moyennant une méthodologie de recherche qualitative. Cette dernière se réalise, d’une part, par une revue documentaire liée aux approches entrepreneuriales coutumières et islamiques&nbsp;; et d’autres parts par la construction d’un modèle entrepreneurial effectual dans une approche islamique M.E.E.A.I L’objectif de cet article théorique, est de procéder par une comparaison entre les pratiques de l’approche entrepreneuriale islamique et ces mêmes pratiques chez les approches coutumières pour relever les points qui les réconcilient. Ensuite, accentuer l’aspect distinctif de l’approche islamique. L’approche islamique continue depuis plus de 15 siècles de garder une place dans le monde des affaires&nbsp;; tout en préservant les mêmes sources de sa législation. Et pour prendre en considération la sphère dans laquelle elles sont appliquées, ces sources, ont été réajustées et revues par le biais de la jurisprudence islamique sans sortir du cadre de la Chari’a islamique. D’autres approches coutumières ont dû parcourir des siècles pour avoir un voisinage de cette approche islamique, en matière d’entrepreneuriat socialement responsable, entrepreneuriat féminin, et le montage d’institutions qui assurent le bon fonctionnement de l’entrepreneuriat. &nbsp; &nbsp; Classification JEL : &nbsp;B59 Type de l’article&nbsp;: Article théorique

Asymptotic analysis of pollution filtration through thin random fissures between two porous media

We describe the asymptotic behaviour of a filtration problem from a contaminated porous medium to a non-contaminated porous medium through thin vertical fissures of fixed height h>0, of random thinness of order {\epsilon} and which are $\epsilon$-periodically distributed. We compute the limit velocity of the flow and the limit flux of pollutant at the interfaces between the two porous media and the intermediate one

Microbial Consortia as Plant Biostimulants: Definition, Concept, Categories, and Regulation.

peer reviewedMicrobial consortia include cellulolytic bacteria, fungi, yeasts, and microbial-based biofilms which can be found in, or constituents of, food products, soils, wastewater, etc. flourishing in nature. The characterization, design, and management of these consortia are feasible, and their application in diverse fields, such as agriculture, is under research. During the last decades, considerable attention has been paid to microbial consortia as plant bio stimulants. They are an ecological alternative for sustainable agriculture and a win-win strategy to grow valuable plants without releasing fertilizers and/or pesticides into the environment. Plant biostimulants are natural preparations, of a diverse class of substances and/or micro-organisms, which positively affect plant growth conditions, stimulate natural processes, improve yield and chemical composition, and increase tolerance to biotic and abiotic stress. The purpose of this chapter is to provide an up-to-date overview of microbial consortia used as plant biostimulants. Aiming to describe the emerging definitions of plant bio stimulants, their concept, the functional categories, and their potential application as a significant tool for modern eco-friend agriculture. The chapter focuses also on reporting the regulatory framework and the current market situation of plant bio stimulants, as well as their advances in research

Assessing the Interplay between Weather and Septoria Leaf Blotch Severity on Lower Leaves on the Disease Risk on Upper Leaves in Winter Wheat

peer reviewedSeptoria leaf blotch (SLB) is among the most damaging foliar diseases of wheat worldwide. In this study, data for seven cropping seasons (2003–2009) at four representative wheat-growing sites in the Grand-Duchy of Luxembourg (GDL) were used to assess SLB risk on the three upper leaves (L3 to L1, L1 being the flag leaf) based on the combination of conducive weather conditions, simulated potential daily infection events by Zymoseptoria tritici, and SLB severity on lower leaves between stem elongation and mid-flowering. Results indicated that the variability in SLB severity on L3 to L1 at soft dough was significantly (p < 0.05) influenced by the disease severity on the lower leaf L5 at L3 emergence and the sum of daily mean air temperature between stem elongation and mid-flowering. Moreover, analyzing the predictive power of these variables through multiple linear regression indicated that the disease severity on L5 at L3 emergence and mild weather conditions between stem elongation and mid-flowering critically influenced the progress of SLB later in the season. Such results can help fine tune weather-based SLB risk models to guide optimal timing of fungicide application in winter wheat fields and ensure economic and ecological benefits