Provincial Research and Advisory Center for Agriculture and Horticulture

Belgium

Provincial Research and Advisory Center for Agriculture and Horticulture

Belgium
SEARCH FILTERS
Time filter
Source Type

Declercq B.,Ghent University | Declercq B.,Provincial Research and Advisory Center for Agriculture and Horticulture | Devlamynck J.,Ghent University | de Vleesschauwer D.,Ghent University | And 4 more authors.
Journal of Phytopathology | Year: 2012

White tip, caused by Phytophthora porri, is a devastating disease in the autumn and winter production of leek (Allium porrum) in Europe. This study investigated the disease cycle of P. porri in laboratory and field conditions. Oospores readily germinated in the presence of non-sterile soil extract at any temperature between 4 and 22°C, with the formation of sporangia which released zoospores. The zoospores survived at least 7weeks in water at a temperature range of 0 till 24°C. Microscopic examinations revealed that zoospores encysted and germinated on the leek leaf surface and hyphae entered the leaf directly through stomata or by penetrating via appressoria. Oospores were formed in the leaves within 6days, while sporangia were not produced. By monitoring disease progress in fields with a different cropping history of leek, it could be deduced that P. porri survives in soil for up to 4years. Disease progress during three consecutive years was correlated with average daily rainfall in the infection period. Disease incidence on leek was reduced when rain splash was excluded by growing the plants in an open hoop greenhouse. Based on these findings, we propose a disease cycle for P. porri in which oospores germinate in puddles, and zoospores reach the leaves by rain splash and survive in water in the leaf axils, from where they infect the plant by direct penetration or via stomata. When conditions become unfavourable, oospores are produced in the leaves which again reach the soil when leaves decay. Secondary spread of the disease by sporangia does not seem to be important. © 2011 Blackwell Verlag GmbH.


Brusselman E.,Belgium Institute for Agricultural and Fisheries Research | Beck B.,Ghent University | Pollet S.,Provincial Research and Advisory Center for Agriculture and Horticulture | Temmerman F.,Provincial Research and Advisory Center for Agriculture and Horticulture | And 4 more authors.
Pest Management Science | Year: 2012

Background: The present study compared entomopathogenic nematode delivery at the base of savoy cabbage and cauliflower, at the lower side of savoy cabbage and cauliflower leaves and in leek stems and the ground deposition using a five-nozzle spray boom equipped with an ISO 08 flat fan, an air induction flat fan and Twinjet spray nozzles. Additionally, an air support system and a row application system were evaluated. Results: Approximately 40% of the applied nematodes did not reach the foot of the cabbage plants. The use of an air support system or a row application system improved nematode deposition at the savoy cabbage base. Relative nematode deposition on the lower side of savoy cabbage leaves was 27.20%, while only 2.64% of the applied nematodes reached the lower side of cauliflower leaves. After spraying leek with a standard boom, a low relative nematode deposition (26.64%) was measured in the leek stem. Nozzle type affected the distribution of nematodes in droplet spots. Conclusion: Nozzle type has a minor effect on the number of entomopathogenic nematodes delivered on difficult-to-reach targets. The use of modified spray application techniques directing the spray to the target site are necessary to increase the chances of contact of entomopathogenic nematodes with their target. © 2011 Society of Chemical Industry.


Holvoet K.,Ghent University | Sampers I.,Ghent University | Seynnaeve M.,Provincial Research and Advisory Center for Agriculture and Horticulture | Jacxsens L.,Ghent University | Uyttendaele M.,Ghent University
International Journal of Environmental Research and Public Health | Year: 2015

The aim of this study was to gain insight into potential differences in risk factors for microbial contamination in greenhouse versus open field lettuce production. Information was collected on sources, testing, and monitoring and if applicable, treatment of irrigation and harvest rinsing water. These data were combined with results of analysis on the levels of Escherichia coli as a fecal indicator organism and the presence of enteric bacterial pathogens on both lettuce crops and environmental samples. Enterohemorragic Escherichia coli (EHEC) PCR signals (vt1 or vt2 positive and eae positive), Campylobacter spp., and Salmonella spp. isolates were more often obtained from irrigation water sampled from open field farms (21/45, 46.7%) versus from greenhouse production (9/75, 12.0%). The open field production was shown to be more prone to fecal contamination as the number of lettuce samples and irrigation water with elevated E. coli was significantly higher. Farmers comply with generic guidelines on good agricultural practices available at the national level, but monitoring of microbial quality, and if applicable appropriateness of water treatment, or water used for irrigation or at harvest is restricted. These results indicate the need for further elaboration of specific guidelines and control measures for leafy greens with regard to microbial hazards. © 2014 by the authors; licensee MDPI, Basel, Switzerland.


Holvoet K.,Ghent University | Sampers I.,Ghent University | Seynnaeve M.,Provincial Research and Advisory Center for Agriculture and Horticulture | Uyttendaele M.,Ghent University
International Journal of Food Microbiology | Year: 2014

Eight Belgian lettuce farms located in the West Flanders were sampled to establish the relationships between levels of indicator bacteria, detection of enteric zoonotic pathogens and the temperature and precipitation during primary production. Pathogenic bacteria (PCR EHEC positives, Salmonella spp. or Campylobacter spp.) and indicator bacteria (total psychrotrophic aerobic plate count (TPAC), total coliforms, Escherichia coli, enterococci) were determined over a period of one and a half year from seedling leaves, peat-soil of the seedling, lettuce crops, field soil and irrigation water. Neither Salmonella isolates nor PCR EHEC signals were detected from lettuce although one out of 92 field soil samples contained Salmonella spp. and five soil samples provided PCR positives for EHEC virulence factors (vt1 or vt2 and eae gene). A low prevalence of Campylobacter (8/88) was noted in lettuce. It was shown that irrigation water is a major risk factor with regard to the bacterial contamination of the fresh produce as the water samples showed on a regular basis E. coli presence (59.2% of samples. ≥. 1. CFU/100. ml) and occasionally detection of pathogens (25%, n=30/120), in particular Campylobacter spp. The highest correlations between indicator bacteria, pathogens, temperature and the amount of precipitation were observed for the water samples in contrast to the soil or lettuce samples where no correlations were observed. The high correlations between E. coli, total coliforms and enterococci in the water implicated redundancy between analyses. Presence of elevated levels of E. coli increased the probability for the presence of pathogens (Campylobacter spp., EHEC and Salmonella spp.), but had a low to moderate predictive value on the actual presence of pathogens. The presence of pathogens and indicator bacteria in the water samples showed a seasonal effect as they tend to be more present during the months with higher temperature. © 2013 Elsevier B.V.


Brusselman E.,Belgium Institute for Agricultural and Fisheries Research | Beck B.,Ghent University | Temmerman F.,Provincial Research and Advisory Center for Agriculture and Horticulture | Pollet S.,Provincial Research and Advisory Center for Agriculture and Horticulture | And 4 more authors.
American Society of Agricultural and Biological Engineers Annual International Meeting 2010, ASABE 2010 | Year: 2010

Application technology for biological insecticides like entomopathogenic nematodes (EPN) has been a relatively neglected area. One of the major considerations involved with the selection and use of an application system should be the application distribution pattern. While completely uniform distribution of the nematodes is not entirely essential to their success in soil applications, because there the nematodes can move short distances on their own, a uniform distribution is more important in foliar EPN applications. The present study examined the volumetric distribution pattern of Steinernema feltiae beneath a single standard flat fan, air induction, deflector and twinjet spray nozzle. A comparison with the distribution of a chemical tracer was made to reveal possible distribution problems. Droplet size spectra of the nozzles were measured and linked with the distribution results. A theoretical calculation of the coefficient of variation of the nematode distribution beneath a spray boom was performed. Finally, the actual spray pattern of the EPN on a horizontal surface beneath a spray boom was studied. We can conclude that the volumetric distribution pattern of EPN is influenced by nozzle type and is different from the volumetric distribution pattern of a chemical compound. By the spray overlap using a spray boom, differences in nematode distribution are however decreased to an acceptable level. Nozzle type significantly influences the number of nematodes deposited on a horizontal Petri dish and their distribution within the droplets. Future experiments are needed to reveal if the measured differences in coverage due to nozzle type will result in significant differences in pest control.


Declercq B.,Ghent University | Van Buyten E.,Ghent University | Claeys S.,Ghent University | Cap N.,Vegetable Research Center | And 3 more authors.
European Journal of Plant Pathology | Year: 2010

White tip, caused by Phytophthora porri, is a destructive disease in the cultivation of European leek (Allium porrum). P. porri and closely related species such as P. brassicae, P. primulae and P. syringae belong to the phylogenetic clade 8b within the genus Phytophthora. The objectives of this study were to establish the position of P. porri and closely related species within the Phytophthora clade 8b; to study genetic variation among P. porri isolates from leek and closely related species and to test the hypothesis that host-driven speciation has occurred within this clade. AFLP analysis could clearly make a distinction between isolates of P. porri from Allium species and related Phytophthora species such as P. brassicae, P. syringae and P. primulae. DNA similarity and cluster analysis based on 353 markers demonstrated little genetic diversity within the P. porri population from Allium species although Belgian and Dutch P. porri isolates from leek could be distinguished from Japanese P. porri isolates from other Allium species and the P. porri isolate from carrot. Our results point to incipient speciation within the P. porri isolates, which could have been driven by the host plant or by geographic isolation. ITS sequence analysis confirmed the results obtained by AFLP and showed a close relationship between P. porri isolates from Allium and P. primulae and between the P. porri isolate from carrot and P. brassicae. We hypothesize that interspecific hybridization has occurred within this clade. © 2010 KNPV.


Cottyn B.,Belgium Institute for Agricultural and Fisheries Research | Baeyen S.,Belgium Institute for Agricultural and Fisheries Research | Pauwelyn E.,Provincial Research and Advisory Center for Agriculture and Horticulture | Pauwelyn E.,Ghent University | And 5 more authors.
Plant Pathology | Year: 2011

Midrib rot is an emerging disease in greenhouse production of lettuce caused by Pseudomonas cichorii, and probably introduced through contaminated irrigation water. Concentrations of 100CFUmL -1 are enough to induce the typical midrib rot symptoms. A sensitive real-time PCR assay was developed, based on a 90-bp amplicon from the pathogenicity gene cluster hrcRST and a Taqman Minor Groove Binding probe. Specificity of the assay was tested with 39 P. cichorii strains, including the type strain, and 89 strains from 83 other Pseudomonas species. The relationship between detection signals and P. cichorii DNA concentrations was linear over 6-logs. Detection threshold with excellent reproducibility was 500fg of DNA or about 70 genome copies. Sample preparation and DNA isolation were optimized to allow detection in 1L water samples. The assay was first evaluated with greenhouse irrigation water spiked with serial dilutions of P. cichorii. The calculated cell numbers obtained with real-time PCR were 10-fold lower than plate counts of actual spiked cells. However, the assay consistently detected 100CFU per reaction, corresponding to the detection of 1CFUmL -1 of irrigation water, which is well below the concentration needed for midrib rot infection. Finally, the assay proved to be valuable for detecting infective P. cichorii concentrations in the irrigation water of a commercial lettuce production greenhouse. © 2010 The Authors. Plant Pathology © 2010 BSPP.


Pauwelyn E.,Ghent University | Pauwelyn E.,Provincial Research and Advisory Center for Agriculture and Horticulture | Vanhouteghem K.,Ghent University | Vanhouteghem K.,Provincial Research and Advisory Center for Agriculture and Horticulture | And 5 more authors.
Journal of Phytopathology | Year: 2011

Bacterial midrib rot, caused by Pseudomonas cichorii, has become a serious threat to the production of greenhouse butterhead lettuce (Lactuca sativa L. var. capitata) in Belgium. Currently, there are no strategies for controlling this pathogen. Therefore, greenhouse experiments were conducted to obtain more knowledge about the epidemiology of P. cichorii on butterhead lettuce. Greenhouse butterhead lettuce becomes susceptible to lettuce midrib rot infections at head formation, and a single overhead irrigation with water containing 10 2CFU/ml P. cichorii was sufficient to cause disease. The use of surface drip irrigation instead of overhead sprinkler irrigation significantly reduced midrib rot incidence in the greenhouse. P. cichorii isolates can be divided into subgroups based on BOX-PCR genomic fingerprinting, with isolates belonging to subgroup C1 and C2 being more virulent than those of (or related to) subgroup C3. P. cichorii infections with distinct symptoms comparable to midrib rot have also been observed on field-grown crisphead lettuce in California and Japan which, respectively, are referred to as 'varnish spot' or 'tar'. We showed that symptom expression is strongly influenced by the lettuce cultivar group, irrespective of the P. cichorii isolate, resulting in varnish spot/tar on crisphead lettuce and midrib rot on butterhead or cutting group lettuce. © 2010 Blackwell Verlag GmbH.


PubMed | Provincial Research and Advisory Center for Agriculture and Horticulture and Ghent University
Type: | Journal: International journal of food microbiology | Year: 2013

Eight Belgian lettuce farms located in the West Flanders were sampled to establish the relationships between levels of indicator bacteria, detection of enteric zoonotic pathogens and the temperature and precipitation during primary production. Pathogenic bacteria (PCR EHEC positives, Salmonella spp. or Campylobacter spp.) and indicator bacteria (total psychrotrophic aerobic plate count (TPAC), total coliforms, Escherichia coli, enterococci) were determined over a period of one and a half year from seedling leaves, peat-soil of the seedling, lettuce crops, field soil and irrigation water. Neither Salmonella isolates nor PCR EHEC signals were detected from lettuce although one out of 92 field soil samples contained Salmonella spp. and five soil samples provided PCR positives for EHEC virulence factors (vt1 or vt2 and eae gene). A low prevalence of Campylobacter (8/88) was noted in lettuce. It was shown that irrigation water is a major risk factor with regard to the bacterial contamination of the fresh produce as the water samples showed on a regular basis E. coli presence (59.2% of samples1CFU/100ml) and occasionally detection of pathogens (25%, n=30/120), in particular Campylobacter spp. The highest correlations between indicator bacteria, pathogens, temperature and the amount of precipitation were observed for the water samples in contrast to the soil or lettuce samples where no correlations were observed. The high correlations between E. coli, total coliforms and enterococci in the water implicated redundancy between analyses. Presence of elevated levels of E. coli increased the probability for the presence of pathogens (Campylobacter spp., EHEC and Salmonella spp.), but had a low to moderate predictive value on the actual presence of pathogens. The presence of pathogens and indicator bacteria in the water samples showed a seasonal effect as they tend to be more present during the months with higher temperature.

Loading Provincial Research and Advisory Center for Agriculture and Horticulture collaborators
Loading Provincial Research and Advisory Center for Agriculture and Horticulture collaborators