Comparison between two different pretreatment technologies of rice straw fibers prior to fiberboard manufacturing: Twin-screw extrusion and digestion plus defibration

The present work compares two different pretreatment technologies, i.e. twin-screw extrusion, and steaming digestion plus defibration, for producing a thermo-mechanical pulp from rice straw for fiberboard manufacturing. Five liquid/solid ratios from 0.43 to 1.02 were tested for twin-screw extrusion pretreatment, while liquid/solid ratios from 4 to 6 were used for digestion pretreatment. Energy consumption, and characteristics of the extrudates (twin-screw extrusion) and pulps (digestion) (including fiber morphology, chemical composition, thermal properties, apparent and tapped densities, as well as color) were the analyzed parameters for the resulting lignocellulosic fibers. The results showed that liquid/solid ratio had influence on energy consumption of the equipment for both defibrating methods For the twin-screw extrusion method, a lower liquid/solid ratio required more energy while for the digestion plus defibration the effect was the opposite. The corresponding total specific energy consumption ranged from 0.668 kW h/kg to 0.946 kW h/kg dry matter for twin-screw extrusion, and from 6.176 kW h/kg to 8.52 kW h/kg dry matter for digestion plus defibration. Thus, the pulping method consumed about nine times more energy than that of the twin-screw extrusion. In addition, for twin-screw extrusion, the liquid/solid ratio did not have a substantial effect on fiber characteristics with similar chemical compositions and thermal properties. For twin-screw extrusion, the energy consumption was 37% reduced when the liquid/solid ratio was increased from 0.43 to 1.02. Instead, for digestion plus defibration, the energy increase was 38% when the liquid/solid ratio increased from 4 to 6

Production of fiberboard from rice straw thermomechanical extrudates by thermopressing : influence of fiber morphology, water and lignin content

The objective of this study was to investigate the influence of fiber morphology and molding parameters on the mechanical and physical properties of fiberboards made from rice straw. The rice straw was thermomechanically treated with a twin-screw extruder. Three parameters were investigated: the amount of water added at molding (0–20%), lignin content (0–25%), and the liquid/solid ratio used for extrudate production (0.33–1.07). A Doehlert experimental design was used to evaluate the effects of these factors on fiberboard properties. A liquid/solid ratio of 0.4 at extrudate production, the addition of 5% water at molding, and a lignin content of 8.9% were found to be optimal for bending properties. The fiberboard produced in these conditions had a density of 1414 kg/m3 (i.e. the densest board). Maximum flexural strength and elastic modulus were 50.3 MPa and 8.6 GPa, respectively. A thickness swelling of 23.6% and 17.6% water absorption were observed. The statistical analysis suggested that a good compromise between density and flexural properties could be obtained with the addition of 0% water, a lignin content of 25% and a liquid/solid ratio of 0.33 at extrudate production. Polynomial models suggested that the fiberboards produced in such conditions would have a maximum flexural strength of 50 MPa, an elastic modulus of 6.0 GPa, a density of 1102 kg/m3, and a thickness swelling of 24%

Epidemiology sf Sharka disease in France

International audiencePlum pox virus was first detected in France in the 1960s. Both PPV-D and PPV-M strains are present but epidemics related to the PPV-M strain detected in the late 1980s are the most problematic. The two PPV strains have unequal distributions in peach and apricot orchards and different prevalences. More than 20 different aphid species have been identified as vectors of PPV but most of them do not colonize Prunus species. Thus, aphids involved in the spread of PPV in orchards are essentially visiting aphids. The main sources of inoculum for the vectors are leaves and fruits of infected stone-fruit trees. Spontaneous, wild and ornamental Prunus species such as Prunus dulcis, P. spinosa or P. pissardii are susceptible to PPV isolates found in France but their role as a reservoir in sharka epidemics is probably negligible. The disease spreads rapidly in orchards but the rate of progression may vary according to the identity of the PPV strain and the Prunus species. Analysis of spatial patterns of disease has shown that secondary spread by aphids frequently occurs over short distances in the orchards (aggregated patterns) but also that dissemination at longer distances (of several hundred metres) is a common event

Data on the life cycle of Cacopsylla pruni, Psyllidae vector of european stone fruit yellows phytoplasma, in France

International audienceA network was created in France to obtain data on the seasonal activity of the psyllid Cacopsylla pruni, vector of European stone fruit yellows phytoplasma. C. pruni was collected on Prunus plants by beating trays. The insect was found in every prospected area. The reimmigrants (adults that have overwintered) were found on Prunus from February to May and the new generation from May to June. Not any C. pruni was found on Prunus after July. Prunus spinosa appeared the preferred host plant compared to the other monitored Prunus. The data are discussed in relation to the control of the phytoplasma disease

L'enroulement chlorotique de l'abricotier : le point sur le vecteur Cacopsylla plruni et les implications relatives à la lutte contre la maladie

UMR BGPI Equipe 6 dossier abricot et pruneNational audienc

Influence de la vitesse et de la direction du vent sur la capture des pucerons ailes par un piege a fils englues

National audienceThe influence of wind speed on the trapping efficiency of a sticky fishing-line trap has been studied by the mean of double traps fixed on a rotating stand directed by a wind vane. Analysis of the catches of aphids released to windward of the traps showed a good linear negative correlation (R = 0.94) between the proportions of trapped aphids and the speed of the wind. The influence of the direction of the wind has been studied indirectly using traps with different spacing between the sticky threads. It is deduced that the relative proportions of the different species did not change, and that the number of trapped aphids is likely the same up to an angle of 43°, at least, of the wind relative to the plane of the trap. Some practical considerations about the use of the sticky fishing-line traps are deduced from these results

Aphids can acquire plum pox virus from infected fruits

UMR BGPI Equipe 6International audienceStone fruit trees can produce fruits even after Plum pox virus (PPV) infection. These fruits can be left in the orchard if unmarketable or marketed if symptomless, elsewhere and possibly thrown away at this new place. Hence, if infected fruits can be a virus source for aphids, they provide a way of dissemination of PPV. To test the hypothesis that PPV could be acquired from infected fruits, we used apricots and peaches produced from trees infected by PPV strains D and M and maintained under an insect proof screenhouse. Four stages of maturity were assessed, from the beginning of fruit formation to a post-maturity stage. Transmissions were carried out by Myzus persicae. Test plants were seedlings of Prunus persicae cv GF 305. We demonstrate that aphids can transmit PPV from infected apricots or peaches to peach seedlings, even from symptomless fruits. Both PPV strains were transmitted. Transmissions were obtained at all the stages of fruit ripening, even with rotting fruits. To demonstrate that aphids can land on fruits, healthy fruits were glued and exposed in trays under field conditions. Aphids belonging to several species (including known PPV vectors) were caught. Infected fruits can thus be a virus source for aphids and can provide a pathway for PPV dissemination

The behaviour of alate aphids inside a Prunus orchard : an element to take into account in Plum Pox Virus spread ?

National audienceAphid-borne viruses are depending on flight behaviour of their vectors for spreading. When spread takes place in orchards as it is the case for plum pox virus, the flight behaviour of aphids can be modified by the effect of the orchard on the wind. The aim of this experiment was to document both the effect of the orchard on wind speed and its consequence on aphid flight behaviour. Data on the wind speeds inside an apricot orchard demonstrated that the wind speed at the foliage level and at the bottom of the trees is decreased under the value of 1 m/s (speed limit for actively oriented aphid flight). As a consequence, aphids have the possibility to make actively oriented flights inside the orchard most of the time. This was confirmed by a capture-recapture experiment with marked aphids. It can be deduced from the results that the geometry of orchards should be taken into account for analysing spatial pattern of virus spread

Spatial Pattern and genetic structure of PPV-M in a delimited area of stone fruit orchards in southern France

International audienceThe spatial pattern and genetic structure of the Plum pox virus strain M have been studied in a delimited area of ca. 450 ha of stone fruit orchards. In this area, the Sharka disease spread undetected until its discovery in 2004. An exhaustive mapping of the diseased trees was performed using GIS technology in 2004 and 2005. Samples constituted by a pool of flowers or leaves were taken from each diseased tree. Analyses of the genetic structure of the virus populations have been initiated using Capillary Electrophoresis-Single Strand Conformation Polymorphism (CE-SSCP). Each haplotype detected by SSCP was further characterized by direct sequencing of the PCR products. The genetic diversity of PPV populations was low with one major haplotype representing 73% of the collected samples. Three other haplotypes from the 37 detected were found on more than 10 trees. Despite this low diversity, genetic variation had a clear spatial structure

Vector control of fruit tree viruses and phytoplasmas

BGPI : équipe 6.International audienceThis impressive new reference presents state-of-the-art biological, molecular, and immunological advances surrounding the causes and strategies for diagnosing and controlling virus diseases of stone fruits. The book’s vivid color images aid in the visual identification of symptomatology while distribution data and improved laboratory techniques provide reliable information and tools for higher diagnostic accuracy. It includes information on economic impact, biology, distribution, taxonomy, genomes, epidemiology, pathogenicity detection, and control measures. This will be an important resource for anyone working with these high-value crops