Agriculture biologique et verrouillage des systèmes de connaissances: Conventionalisation des filières agroalimentaire bio

La question de la co-existence entre deux systèmes bio, l’un porté par les acteurs historiques, l’autre par les nouveaux acteurs agroindustriels, selon un modèle de bifurcation, est traitée à travers l’hypothèse de conventionalisation. Nous utilisons le cas du système Blanc Bleu Belge et de l’élevage bovin bio belge pour montrer que le problème de la co-existence de ces deux systèmes est à la fois une question empirique et une question théorique. Notre argument est que le concept de « référentiel » (au sens de Jobert et Muller, 1987) est non seulement supérieur d’un point de vue théorique mais qu’il ouvre d’intéressantes perspectives pratiques et ceci pour deux raisons. D’abord parce qu’il permet de comprendre la question et l’enjeu de la co-existence de deux systèmes de connaissances différents, l’un alternatif et l’autre conventionnel. Ensuite parce qu’il permet de comprendre les effets d’irréversibilité qui rendent les systèmes conventionnel et biologique incompatibles l’un avec l’autre

Tavelure - Réduire ses traitements

«Bien positionner ses traitements au printemps est la clé pour maîtriser la tavelure avec un minimum de phyto », introduit Laurent Jamar, chercheur belge. Il est vrai que, pour pouvoir contaminer une feuille, une fleur ou un fruit, le champignon responsable de la tavelure a besoin de la présence d’un film d’eau pendant un certain laps de temps, variable selon la température : la protection phytosanitaire doit ainsi être ajustée aux conditions pédoclimatiques, définies si possible au niveau du verger. « Pour cela, deux outils sont essentiels : une station météo, qui enregistre les données localement heure par heure, et un modèle de simulation des infections, qui analyse les données météos enregistrées. Assurer une protection vis-à-vis des contaminations primaires évite ainsi toute intervention pendant l’été ! », poursuit le chercheur

The components of abstracts: The logical structure of abstracts in the areas of materials science and technology and of library and information science

Purpose – The purpose of this study was to examine whether the logical structure of abstracts in the areas of materials science and technology and library and information science comply with the ISO 214 or IMRAD formats, while also suggesting guidelines for components of abstracts. Design/methodology/approach – In the first part of the research the components of abstracts are analysed. The results showed that not all the proposed structural elements are present in the abstracts. Therefore also the improved prototypes and recommended abstracts are developed to examine the satisfaction of readers with different forms of abstracts. According to the results of satisfaction of readers with different forms of abstracts, uniform guidelines for the components of abstracts in accordance with the IMRAD format are proposed. Findings – The introduction (I) should include three sentences of background information. The method (M) should include three sentences of method. The results (R) should include three sentences of results. The discussion (D) should include two sentences of conclusions. The conclusions should present the implications of the results on subjects that were not part of the study, suggestions for possible application of the findings, suggestions for further research work and an evaluation of the research. Originality/value – It is important to emphasize that even if the guidelines for writing abstracts by the individual journal exist, authors do not always take them into account. Therefore, it is important that the abstracts that are actually published in journals were analysed. It is also important that the opinion of researchers was taken into account

Primary scab control using a "during-infection" spray timing and the effect on fruit quality and yield in organic apple production

Organic apple production in Europe depends to a great extent on the use of copper fungicides for scab control (Venturia inaequalis). The objective of this 6-year study (2003-2008) conducted in Belgium was to determine measures for reducing the use of copper fungicides in organic apple production. The effectiveness of a 'during-infection' spray strategy using wettable sulphur (with or without copper), lime sulphur, potassium bicarbonate, silicon and five natural plant extracts (orange peel, soapbark, tea seed, quinoa seed and grapefruit seed) for controlling primary scab was investigated in a split-plot field experiment. Four apple cultivars that express a gradient of partial scab resistance were included: a high scab-susceptible cultivar (cv. 'Pinova'), a medium scab-susceptible cultivar (cv. 'Pirouette') and two old cultivars expressing low to very low scab susceptibility (cvs. 'Reinette Hernaut' and 'Reinette des Capucins'). Apart from these cultivars, four monogenic Vf scab-resistant cultivars (cvs. 'Initial', 'Topaz', 'Zvatava' and 'JN 20/33/58') were also included in the experimental orchard. In order to reduce the amount of fungicide required, two strategies were used: a specific spray timing involving spraying during the infection processes, before fungal penetration, determined by the RIMpro software warning system, and a tunnel sprayer machine for optimal treatment applications. Depending on the year, a total of 8-12 applications were made annually. Under field conditions that were highly conducive disease, low rates of elemental sulphur (≤ 40 kg.ha-1 per year) combined with low rates of copper (≤ 2.1 kg.ha-1 per year) provided the best scab control and reduced scab severity on the leaves and fruits by 85-100%, depending on the year and cultivar, compared with the untreated control. In most cases, the lime sulphur spray treatment, which used more elemental sulphur but did not use copper, provided a similar level of scab control to the combined wettable sulphur and copper spray treatment. Sulphur, potassium bicarbonate and all plant extracts significantly reduced scab severity on leaves and fruits. In general, the treatments increased the yield of the high and medium scab-susceptible cultivars as well as that of the low and very low scab-susceptible cultivars. Under these experimental conditions, none of the treatments caused phytotoxicity, increased fruit russet or led to undesirable soil and fruit residues at harvest. The potential and limitations of "during-infection" spraying as a protection strategy against apple scab in organic farming are discussed

Estimation of starvation and diet variation of the RNA/DNA ratios in field-caught Sardina pilchardus larvae off the north of Spain

The aim of this study was to analyse the general larval condition, to determine the lncidence of starvation and to investigate the effect of time of day on RNA/DNA ratios among field-caught Sardina pilchardus (L.) larvae. The larvae were collected during 4 research cruises off northern Spain, during March, April, May and June 1992. A highly sensitive fluorometric method for nucleic acid quantification was applied to larvae of S. pilchardus. The means of the RNA/DNA ratio were relat~vely high, so the larvae collected off northern Spain were generally in good condition. Low percentages of starving larvae (RNA/DNA ratio less than 1.3), ranging from 0 to 3.23%, were found over the 4 mo. The RNA/DNA ratios were significantly correlated with zooplankton biomass. Larvae collected at night revealed higher RNA/DNA ratios compared to larvae caught during the day. This seems to indicate that there is some endogenous rhythm in the production of RNA. It would then follow that, if there are die1 changes in RNA concentrations, average RNA Indices can be unrepresentative if there IS any day/night bias in sampling

CREATION ET EXPERIMENTATION DE VARIETES DE POMMES ADAPTEES A L’AGRICULTURE BIOLOGIQUE

Our apple breeding program is based entirely on the results of our work to safeguard, evaluate and valorize the rich heritage of apple tree genetic resources in our regions. Since 1975, no fewer than 1800 introductions have been collected in our collections and, taking into account duplicates, errors and synonyms, this represents a total of about 850 distinct cultivars. These are systematically evaluated in experimental orchards that do not undergo any treatment. Some cultivars that are highlighted for their high level of resistance to the main diseases as well as for their agronomic and quality characteristics of trees and fruits are used as parents. Our priorities are mainly focused on the expansion of the apple's genetic base, polygenic resistance to the main diseases (scab, powdery mildew, canker) and a whole series of characteristics present in certain old and peasant varieties such as long natural conservation, rusticity, robustness, frugality, nitrogen efficiency, tree architecture and the nutritional qualities and properties of the fruit. These parents are then crossed with varieties, often more commercial, which offer advantages in terms of speed of fruiting, yield, flesh quality and tree architecture. The current plant breeding program is based on extensive methodological work that has been developed specifically to select materials with partial disease resistance that express good potential for adaptation to simple and 'low-input' crop conditions. About sixty elite selections from our work are currently being tested in organic farming and are compared with 48 other new commercial varieties in order to look for varietal alternatives that are much better adapted to organic production than those currently being grown. Partial results of about twenty selections and varieties are presented, including results relating to the sustainability of a panel of varieties carrying the Vf gene