Sint-Katelijne-Waver, Belgium
Sint-Katelijne-Waver, Belgium

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Vanhassel P.,Inagro | Bleyaert P.,Inagro | Van Lommel J.,Research Station for Vegetable Production | Vandevelde I.,Research Station for Vegetable Production | And 5 more authors.
Acta Horticulturae | Year: 2015

The physiological disorder tipburn remains a constant threat for growers of butterhead lettuce in greenhouses. In standard soil cultivation, tipburn is controlled reasonably well by using traditional growing methods, combined with the selection of tolerant cultivars. However, when applying novel growing techniques such as hydroponics, current practices to prevent tipburn show to be no longer sufficient. Therefore, a research project was started up, aiming at the development of a more rational tipburn prevention strategy. In the first year, tipburn occurrence was studied in successive soil-grown lettuce crops at two locations. Out of several environmental factors, which might induce tipburn according to literature, low nightly air humidity (RHn) appeared to be the most important one in commercial growing conditions. Several successive experiments with hydroponic lettuce (NFT) confirmed that maintaining RHn at a high level is an efficient measure to decrease tipburn occurrence. Whereas 60 to 100% of the control plants was affected by tipburn, maintaining RHn above 95% markedly reduced tipburn injury to 3 to 50%, respectively. This effect was associated with an improved Ca transport to the leaf margins (1 cm zone) of young lettuce leaves and values higher than 2-3 g Ca kg-1 DM were obtained. The most efficient technique to decrease tipburn occurrence by raising RHn was the combination of water spraying underneath the gullies with nebulization above the plants. Second best techniques were the mere spraying of water under the gullies and covering the plants with plastic foil.


Rombouts S.,Catholic University of Leuven | Rombouts S.,Belgium Institute for Agricultural and Fisheries Research | Volckaert A.,Vegetable Research Center | Venneman S.,Research Station for Vegetable Production | And 13 more authors.
Frontiers in Microbiology | Year: 2016

Pseudomonas syringae pv. porri, the causative agent of bacterial blight in leek (Allium porrum), is increasingly frequent causing problems in leek cultivation. Because of the current lack of control measures, novel bacteriophages were isolated to control this pathogen using phage therapy. Five novel phages were isolated from infected fields in Flanders (vB_PsyM_KIL1, vB_PsyM_KIL2, vB_PsyM_KIL3, vB_PsyM_KIL4, and vB_PsyM_KIL5), and were complemented with one selected host range mutant phage (vB_PsyM_KIL3b). Genome analysis of the phages revealed genome sizes between 90 and 94 kb and an average GC-content of 44.8%. Phylogenomic networking classified them into a novel clade, named the "KIL-like viruses," related to the Felixounalikevirus genus, together with phage phiPsa374 from P. syringae pv. actinidiae. In vitro characterization demonstrated the stability and lytic potential of these phages. Host range analysis confirmed heterogeneity within P. syringae pv. porri, leading to the development of a phage cocktail with a range that covers the entire set of 41 strains tested. Specific bio-assays demonstrated the in planta efficacy of phages vB_PsyM_KIL1, vB_PsyM_KIL2, vB_PsyM_KIL3, and vB_PsyM_KIL3b. In addition, two parallel field trial experiments on three locations using a phage cocktail of the six phages showed variable results. In one trial, symptom development was attenuated. These data suggest some potential for phage therapy in controlling bacterial blight of leek, pending optimization of formulation and application methods. © 2016 Rombouts, Volckaert, Venneman, Declercq, Vandenheuvel, Allonsius, Van Malderghem, Jang, Briers, Noben, Klumpp, Van Vaerenbergh, Maes and Lavigne.


Hanssen I.M.,Scientia Terrae Research Institute | Gutierrez-Aguirre I.,Slovenian National Institute of Biology | Paeleman A.,Scientia Terrae Research Institute | Goen K.,Research Center Hoogstraten | And 5 more authors.
Plant Pathology | Year: 2010

The potential of three mild Pepino mosaic virus (PepMV) isolates, belonging to the CH2, EU and LP genotypes, to protect a tomato (Solanum lycopersicum) crop against an aggressive challenge isolate of the CH2 genotype was assessed in greenhouse trials and PepMV symptoms were rated at regular time points. After challenge infection, enhanced symptom display was recorded in plants that were pre-inoculated with a protector isolate belonging to a different genotype (EU, LP) from the challenge isolate. A quantitative genotype-specific TaqMan assay revealed that in these plants, the accumulation of the challenge isolate only temporarily slowed down. By contrast, efficient cross-protection was obtained using the mild isolate of the CH2 genotype, and in this case the challenge isolate was barely detectable in the pre-inoculated plants. These results suggest that the interaction between PepMV isolates largely depends on RNA sequence homology and that post-transcriptional gene silencing plays an important role in cross-protection. © 2009 BSPP.


PubMed | Scientia Terrae Research Institute, Ghent University, Research Station for Vegetable Production, Tomato Research and Belgium Institute for Agricultural and Fisheries Research
Type: Journal Article | Journal: Pest management science | Year: 2016

The zoophytophagous predator Macrolophus pygmaeus Rambur (Hemiptera: Miridae) is a successful biocontrol agent against several pest species in protected tomato crops. This predator is considered to be harmless for the crop. However, in recent years, Heteroptera feeding punctures on tomato fruit in Belgian and Dutch greenhouses have been misinterpreted as Pepino mosaic virus (PepMV) symptoms. In this study, three hypotheses were tested: (1) M. pygmaeus causes fruit damage that increases with population density and surpasses economic thresholds; (2) the presence of prey or alternative prey reduces the damage; (3) an infection of the tomato plants by PepMV triggers or aggravates M. pygmaeus fruit damage.At increasing M. pygmaeus densities, the severity of fruit damage increased from a few dimples towards yellowish discoloration and deformed fruits. A correlation with an infection with PepMV was found. The severity of the symptoms was independent of the presence of prey. A minimum economic density threshold was estimated at 0.32 M. pygmaeus per leaf.M. pygmaeus can cause economic damage to tomato fruits at densities common in practice. An infection of the plants with PepMV enhances fruit symptoms significantly. Interacting plant defence responses are most likely the key to explaining this, although confirmation is required. 2015 Society of Chemical Industry.


Van Den Bulck N.,Flemish Institute for Technological Research | Coomans M.,Flemish Institute for Technological Research | Wittemans L.,Research Station for Vegetable Production | Hanssens J.,Ghent University | Steppe K.,Ghent University
Energy and Buildings | Year: 2013

Greenhouse cultivation is an intensive part of horticulture in Flanders in which large production volumes are accompanied by significant energy consumptions. Demand for energy efficient solutions is rising due to fluctuations and increases in energy prices, ongoing pressure from international competition and incentives from governments in the scope of climate change. Over a two-year period, a compact ventilation concept was monitored in a Belgian semi-closed greenhouse. The installation was one of the first ventilation concepts in Belgium and is based on intensive thermal screening in combination with controlled ventilation. Air flow rates, indoor and outdoor climatic parameters were monitored as well as the energy flows of the ventilation unit, the energy demand of the greenhouse and the crop results. The measured energy consumption of the concept was 9.6% higher than the reference case in 2010, partly due to its location within the greenhouse complex. However, during the second growing season of 2011, two more similar compartments were compared, showing the potential of the ventilation concept with a 12% energy saving. In addition, improved crop growing conditions become possible as the installation allows for a better control of the greenhouse climate. © 2012 Elsevier B.V.


Hanssens J.,Ghent University | De Swaef T.,Ghent University | Wittemans L.,Research Station for Vegetable Production | Goen K.,Horticulture Research Center Hoogstraten | And 3 more authors.
Acta Horticulturae | Year: 2012

Maintaining good plant water status is crucial for optimal production and quality of tomato in greenhouses. Various new climate control technologies have been introduced to make greenhouse cultivation more energy-efficient, resulting in a modified greenhouse climate. Recently, there has been growing interest in the use of plant-based methods to steer the climate. Monitoring stem diameter variations (SDV) has been extensively studied in tree species, but is also very promising for herbaceous crops. Stem and fruit diameter variations provide crucial information about plant water status, though unambiguous interpretation of these dynamics is often difficult. Mechanistic modelling can help to elucidate the mechanisms driving plant behaviour and is therefore an important tool for interpreting the dynamic response of the plants to changes in microclimate. In the present study, tomato plants (Solanum lycopersicum L.) were subjected to elevated air temperature (Ta) and vapour pressure deficit (VPD), while SDV, sap flow and fruit growth were continuously monitored. Results indicated that stem shrinkage became more pronounced and fruits shrank during periods of high Ta and VPD. Simulation results showed that reduced fruit growth resulted from both increased fruit transpiration and decreased phloem inflow. Moreover, xylem backflow appeared when Ta and VPD reached maximum values. It was demonstrated that the reduced fruit growth resulted mainly from changes in stem water potential, rather than fruit water potential.


Van Damme V.M.,Belgium Institute for Agricultural and Fisheries Research | Van Damme V.M.,Ghent University | Beck B.K.E.G.,Belgium Institute for Agricultural and Fisheries Research | Berckmoes E.,Research Station for Vegetable Production | And 8 more authors.
Pest Management Science | Year: 2016

BACKGROUND: Previous studies have indicated the control potential of entomopathogenic nematodes (EPNs) against Tuta absoluta. Here, the potential of Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora is studied when applied against larvae of T. absoluta inside leaf mines in tomato leaf discs by means of an automated spray boom. RESULTS: The studied EPN species were effective against all four larval instars of T. absoluta but caused higher mortality in the later instars (e.g. fourth instar: 77.1–97.4% mortality) than in the first instars (36.8–60.0% mortality). Overall, S. feltiae and S. carpocapsae yielded better results than H. bacteriophora. Steinernema carpocapsae and H. bacteriophora performed better at 25 °C (causing 55.3 and 97.4% mortality respectively) than at 18 °C (causing 12.5 and 34.2% mortality respectively), whereas S. feltiae caused 100% mortality at both temperatures. Under optimal spraying conditions and with the use of Addit and Silwet L-77 adjuvants, a reduced dosage of 6.8 infective juveniles (IJs) cm−2 yielded equally good control as a recommended dosage of 27.3 IJs cm−2. CONCLUSION: Under laboratory conditions, S. feltiae and S. carpocapsae showed good potential against the larvae of T. absoluta inside tomato leaf mines. Results need to be confirmed in greenhouse experiments. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry


Van Damme V.,Ghent University | Van Damme V.,Belgium Institute for Agricultural and Fisheries Research | Berkvens N.,Belgium Institute for Agricultural and Fisheries Research | Moerkens R.,Tomato Research | And 6 more authors.
Journal of Pest Science | Year: 2015

The South American tomato leafminer Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) is a devastating pest in tomato crops. After having spread rapidly in the Mediterranean area since its first detection in 2006, it has recently become established in greenhouses in Western Europe. It was assumed that the low temperatures commonly associated with the winters in this area would prevent this exotic species from successful overwintering. However, the observed presence of T. absoluta at the start of the growing season in Belgium sparked a study on its potential to overwinter in Western Europe. In this study, the insect’s cold hardiness and overwintering potential was assessed by determining: (1) the supercooling point (SCP) of larvae, pupae, and adults, (2) the lower lethal time (LT) for these stages at 0 and 5 °C, and (3) the reproductive diapause incidence, as indicated by the reproductive performance of females reared at two temperatures (18 and 25 °C) and two photoperiods [16:8 and 8:16 (L:D) h]. The mean SCP recorded for pupae (−16.7 °C) was significantly higher than for adults (−17.8 °C) and larvae (−18.2 °C). Based on estimates of the LT adults demonstrated better cold hardiness than larvae and pupae at both 0 and 5 °C with the median LT of adults averaging 17.9 and 27.2 days, respectively. No reproductive diapause was observed under the tested regimes. The results of this study indicate that T. absoluta is likely to successfully overwinter between two successive tomato crops in commercial greenhouses in Western Europe. © 2014, Springer-Verlag Berlin Heidelberg.


PubMed | Ghent University, Research Station for Vegetable Production, Tomato Research and Belgium Institute for Agricultural and Fisheries Research
Type: Journal Article | Journal: Pest management science | Year: 2016

Previous studies have indicated the control potential of entomopathogenic nematodes (EPNs) against Tuta absoluta. Here, the potential of Steinernema feltiae, S. carpocapsae and Heterorhabditis bacteriophora is studied when applied against larvae of T. absoluta inside leaf mines in tomato leaf discs by means of an automated spray boom.The studied EPN species were effective against all four larval instars of T. absoluta but caused higher mortality in the later instars (e.g. fourth instar: 77.1-97.4% mortality) than in the first instars (36.8-60.0% mortality). Overall, S. feltiae and S. carpocapsae yielded better results than H. bacteriophora. Steinernema carpocapsae and H. bacteriophora performed better at 25 C (causing 55.3 and 97.4% mortality respectively) than at 18 C (causing 12.5 and 34.2% mortality respectively), whereas S. feltiae caused 100% mortality at both temperatures. Under optimal spraying conditions and with the use of Addit and Silwet L-77 adjuvants, a reduced dosage of 6.8 infective juveniles (IJs) cm(-2) yielded equally good control as a recommended dosage of 27.3 IJs cm(-2) .Under laboratory conditions, S. feltiae and S. carpocapsae showed good potential against the larvae of T. absoluta inside tomato leaf mines. Results need to be confirmed in greenhouse experiments. 2015 Society of Chemical Industry.


Coomans M.,Flemish Institute for Technological Research | Allaerts K.,Flemish Institute for Technological Research | Wittemans L.,Research Station for Vegetable Production | Pinxteren D.,Research Center Hoogstraten
Energy Conversion and Management | Year: 2013

Horticulture is an energy intensive industry when dealing with cold climates such as Western Europe. High energy prices and on-going pressure from international competition are raising demand for energy efficient solutions. In search of reducing greenhouse energy consumption, this study investigates semi-closed systems combining controlled mechanical and natural ventilation with thermal screens. Ventilated greenhouse systems (semi-closed) have been implemented in the greenhouse compartments of two Belgian horticulture research facilities: the Research Station for Vegetable Production Sint-Katelijne-Waver (PSKW) and the Research Center Hoogstraten (PCH). Additionally, two reference compartments were included for comparison of the results. The greenhouses were part of a long-term monitoring campaign in which detailed measurements with a high time resolution were gathered by a central monitoring system. A large amount of data was processed and analysed, including outdoor and indoor climatic parameters, system controls and installation measurements. The ventilated greenhouses obtained energy savings of 13% and 28% for PSKW and PCH respectively, without substantial impact on crop production or indoor climate conditions when compared to the reference compartments. A considerable amount of heat was recovered by the heat recuperation stage in the ventilation unit of PCH, accounting for 12% of the total heat demand. In general, it was demonstrated that the greenhouse heat demand can be reduced significantly by controlled dehumidification with mechanical ventilation, especially during spring and autumn. © 2013 Elsevier Ltd. All rights reserved.

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