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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

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    Restyling Alternaria
    Woudenberg, J.H.C. - \ 2015
    Wageningen University. Promotor(en): Pedro Crous; Pierre de Wit, co-promotor(en): J.Z. Groenewald. - Wageningen : Wageningen University - ISBN 9789462574106 - 250
    alternaria - taxonomie - fylogenie - moleculaire taxonomie - plantenziekteverwekkende schimmels - alternaria - taxonomy - phylogeny - molecular taxonomy - plant pathogenic fungi

    The omnipresent dematiaceous hyphomycete genus Alternaria is associated with a wide variety of substrates including seeds, plants, agricultural products, humans, soil and even the atmosphere. It includes saprophytic, endophytic and pathogenic species, among which multiple plant pathogens, post-harvest pathogens, and human pathogens (causative agents of phaeohyphomycosis and hypersensitivity reactions). Molecular studies reveal that the Alternaria complex comprises nine genera. Within this complex several genera are non-monophyletic and Alternaria species cluster into multiple distinct species clades, which are not always correlated with species-groups based on morphological characteristics. The most commonly reported species in literature and type species of the genus Alternaria, A. alternata, also comprises one such species-group. The small-spored Alternaria species within this group are mainly described based on morphology and / or host-specificity, but are difficult to distinguish based on molecular techniques alone. As A. alternata is considered as one of the most prolific producers of fungal allergens and is reported as pathogen on over 100 host plants, correct species identification is of utmost importance. The research presented in this thesis discusses the taxonomic status of Alternaria and its related genera, with a further focus on the two biggest and most important species complexes; the large-spored A. porri and small-spored A. alternata species complexes. With the phylogenies and classifications presented in this thesis, more robust and understandable taxonomy and nomenclature in Alternaria and allied genera within the Alternaria complex are created.

    Chapter 1 gives a general introduction to the genus Alternaria and related genera. The history of the genus and its economic importance as plant pathogen, post-harvest pathogen, causative agent of phaeohyphomycosis and common allergen causing hypersensitivity reactions are summarized. The introduction of the morphological species complexes, based on characters of the conidia, the pattern of chain formation, and the nature of the apical extensions of conidia are treated. Molecular studies recognise seven Alternaria species-groups within the Alternaria complex. Besides Alternaria, eight other genera are assigned to the Alternaria complex based on molecular and morphological studies.

    Chapter 2 focusses on the relationship of Alternaria and its closely related genera within the broader Alternaria complex. The phylogenetic lineages within the Alternaria complex are delineated based on nucleotide sequence data of parts of the 18S nrDNA (SSU), 28S nrDNA (LSU), the internal transcribed spacer regions 1 and 2 and intervening 5.8S nrDNA (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), RNA polymerase second largest subunit (RPB2) and translation elongation factor 1-alpha (TEF1) gene regions. The phylogenetic data reveal a Stemphylium clade sister to Embellisia annulata and a big Alternaria clade. The Alternaria clade contains six monotypic lineages and 24 internal clades, which are treated as sections of Alternaria. In order to create a stable phylogenetic taxonomy, and supported by i) a well-supported phylogenetic node in multiple analyses, ii) a high-similarity of clades within Alternaria based on SSU, LSU and ITS data, and iii) variation in the clade order between the different gene phylogenies, 13 genera are placed into synonymy with Alternaria. Embellisia annulata is synonymized with Dendryphiella salina, and together with D. arenariae placed in the new genus Paradendryphiella. The sexual genera Clathrospora and Comoclathris, with asexual forms linked to Alternaria, cluster within the Pleosporaceae, as does Alternaria, but outside Alternaria s. str. The genus Alternariaster, described to accommodate Alternaria helianthi, clusters within the Leptosphaeriaceae.

    Chapter 3 describes the reappraisal of the genus Alternariaster. Alternaria helianthi, the causal agent of leaf spot on Helianthus annuus (sunflower) was segregated from Alternaria based on conidial morphology, and placed in the new genus Alternariaster. A multi-gene phylogeny of parts of the ITS, LSU, RPB2 and GAPDH gene regions placed a fungal pathogen associated with leaf spot on Bidens sulphurea (yellow cosmos) in Brazil in close relation with Al. helianthi. Based on the close phylogenetic relation to Al. helianthi, but distinct morphological and pathogenicity characters, the fungal pathogen associated with leaf spot on B. sulphurea is newly described as Al. bidentis.

    Chapter 4 treats the Alternaria species which form the largest section of Alternaria, sect. Porri. This section contains almost all Alternaria species with medium to large conidia with long beaks, some of which are important plant pathogens. A multi-gene phylogeny on parts of the ITS, GAPDH, RPB2, TEF1 and Alternaria major allergen (Alt a 1) gene regions, supplemented with morphological and cultural studies, forms the basis for species recognition in this section. The polyphasic data reveal 63 species in sect. Porri, of which 10 are newly described, and 27 names are synonymized.

    Chapter 5 treats the small-spored Alternaria species, which reside in sect. Alternaria. A lot of confusion around the naming of species within this section exists, since the naming is mostly based on morphology and host-specificity, although the molecular variation is minimal. Whole genome sequencing, combined with transcriptome profiling and multi-gene sequencing of nine gene regions, SSU, LSU, ITS, GAPDH, RPB2, TEF1, Alt a 1, endopolygalacturonase (endoPG) and an anonymous gene region (OPA10-2), is used to create a clear and stable species classification in this section. The nine sequenced Alternaria genomes range in size from 32.0 - 39.1 Mb. The number of repetitive sequences varies significantly, with a relative low percentage of repeats within sect. Alternaria. The genome identity within sect. Alternaria is high, compared to the genome identity for isolates from other sections to the A. alternata reference genome. Similarly, a relative low percentage of single nucleotide polymorphisms (SNPs) were observed in genomic and transcriptomic sequences between isolates from sect. Alternaria, compared to the percentage of SNP’s found in isolates from different sections compared to the A. alternata reference genome. A set of core proteins was extracted from the genome and transcriptome data, and primers were designed on two eukaryotic orthologous group (KOG) protein loci with a relatively low degree of conservation within section Alternaria. The phylogenies from these two gene regions, KOG1058 and KOG1077, could not distinguish the described morphospecies within sect. Alternaria better than the phylogenies based on the nine commonly used gene regions for Alternaria. Based on genome and transcriptome comparisons and molecular phylogenies, Alternaria sect. Alternaria consists of only 11 phylogenetic species and one species complex. Thirty-five morphospecies are synonymized under A. alternata. The subclades that are formed by these isolates are incongruent between the different gene regions sequenced; no two genes show the same groupings for any of the over 100 isolates. A sequence-based identification guide is provided for the species which are now recognized in sect. Alternaria. None of the genes sequenced in this study can distinguish all of the species recognized here on its own.

    Chapter 6 investigates the molecular diversity of indoor Alternaria isolates in the USA, with the help of a phylogeographic / population genetic approach. Isolates collected throughout the USA were identified using ITS, GAPDH and endoPG gene sequencing, followed by genotyping and population genetic inference of the sect. Alternaria isolates and 37 reference isolates, using five microsatellite markers. Phylogenetic analyses revealed that 98 % (153 isolates) of the indoor isolates consisted of species from Alternaria sect. Alternaria. The remaining 2 % (three isolates) represented one sect. Infectoriae and two sect. Pseudoulocladium isolates. From the 153 isolates that belonged to sect. Alternaria, one could be assigned to A. burnsii, 15 to the A. arborescens species complex and the remaining 137 isolates were identified as A. alternata. Based on the microsatellite data, no specific indoor population could be distinguished. Population assignment analyses of the A. alternata isolates suggested that subpopulations did not exist within the sample, which we thus divided into four artificial subpopulations to represent four quadrants of the USA. Genotypic diversity was extremely high for all quadrants and a test for linkage disequilibrium suggested that A. alternata has a cryptic sexual cycle. The SouthWest-USA population displayed the highest level of uniqueness, based on private alleles. Intriguingly, the highest amount of gene flow, between SouthWest-USA and SouthEast-USA, correlated with the west-to-east movement of the antitrade winds. This suggests that indoor A. alternata isolates, although extremely diverse, have a continental distribution and high levels of gene flow over the continent.

    Chapter 7 discusses the data presented in this thesis. The implications of the performed studies are placed in a broader context, with a focus on the relation between morphology and the new species classification based on molecular tools and the use of genome data in contrast to multi-gene data.

    Beheersing Alternaria in de teelt van aardappelen
    Evenhuis, A. ; Schepers, H.T.A.M. - \ 2015
    Wageningen : Praktijkonderzoek Plant & Omgeving, Business Unit AGV
    aardappelen - gewasbescherming - plantenziekteverwekkende schimmels - alternaria - fungiciden - chemische bestrijding - potatoes - plant protection - plant pathogenic fungi - alternaria - fungicides - chemical control
    Uit het onderzoek kwam naar voren dat de effectiviteit van beide referenties tegen Alternaria tegen viel. In hoeverre dit te maken heeft met resistentieontwikkeling binnen de Alternaria populatie is niet duidelijk. In elk geval is het wenselijk om bij de Alternaria bestrijding gebruik te maken van fungiciden met verschillende werkingsmechanismen. Met de toelating van Narita is er voor de Nederlandse telers een extra optie bijgekomen. Phytophthora middelen met een nevenwerking op Alternaria kunnen een goed onderdeel vormen van de bestrijdingsstrategie
    Beheersing Alternaria in de aardappelteelt
    Evenhuis, A. ; Schepers, H.T.A.M. - \ 2014
    Wageningen : Praktijkonderzoek Plant & Omgeving, Business Unit AGV - 14
    akkerbouw - aardappelen - gewasbescherming - alternaria - plantenziekteverwekkende schimmels - schimmelbestrijding - fungiciden - solanum tuberosum - arable farming - potatoes - plant protection - alternaria - plant pathogenic fungi - fungus control - fungicides - solanum tuberosum
    Uit het onderzoek kwam naar voren dat de effectiviteit van beide referenties tegen Alternaria tegen viel. In hoeverre dit te maken heeft met resistentieontwikkeling binnen de Alternaria populatie is niet duidelijk. In elk geval is het wenselijk om bij de Alternaria bestrijding gebruik te maken van fungiciden met verschillende werkingsmechanismen. Met de toelating van Narita is er voor de Nederlandse telers een extra optie bijgekomen. Phytophthora middelen met een nevenwerking op Alternaria kunnen een goed onderdeel vormen van de bestrijdingsstrategie.
    Novel Curvularia species from clinical specimens
    Madrid, H. ; Cunha, K.C. da; Gené, J. ; Dijksterhuis, J. ; Cano, J. ; Sutton, D.A. ; Guarro, J. ; Crous, P.W. - \ 2014
    Persoonia 33 (2014). - ISSN 0031-5850 - p. 48 - 60.
    internal transcribed spacer - allergic bronchopulmonary mycosis - antifungal susceptibility - bipolaris-australiensis - invasive sinusitis - genus curvularia - ribosomal dna - alternaria - cochliobolus - helminthosporium
    The fungal genus Curvularia includes numerous plant pathogens and some emerging opportunistic pathogens of humans. In a previous study we used morphology and sequences of the nuclear ribosomal internal transcribed spacer region (ITS) and the glyceraldehyde-3-phosphate dehydrogenase (gpd) gene to identify species within a set of 99 clinical Curvularia isolates from the USA. Seventy-two isolates could be identified while the remaining 27 isolates belonged in three unclassified clades that were tentatively labelled Curvularia sp. I, II and III. In the present study, we further assess the taxonomic placement of these isolates using sequences of ITS, gpd, the large subunit rDNA, and the second largest subunit of RNA polymerase II. DNA sequence comparisons with a set of 87 isolates representing 33 Curvularia spp. and members of the closely-related genera Bipolaris and Exserohilum revealed that Curvularia sp. I, II and III represent novel lineages in Curvularia. These lineages are morphologically different from the currently accepted species. In the phylogenetic tree, Curvularia sp. I and sp. III were each split into two distinct lineages. Morphology and phylogeny supported the proposal of five new species, to be named C. americana, C. chlamydospora, C. hominis, C. muehlenbeckiae and C. pseudolunata. The concatenated 4-locus phylogeny revealed the existence of six clades in Curvularia, which are associated with particular morphological features. They were named after representative species, namely americana, eragrostidis, hominis, lunata, spicifera and trifolii.
    Occurrence of Alternaria mycotoxins in food products in the The Netherlands
    Lopez Sanchez, P. ; Venema, D.P. ; Rijk, T.C. de; Kok, A. de; Scholten, J. ; Mol, J.G.J. ; Nijs, W.C.M. de - \ 2013
    alternaria - voedselveiligheid - voedselanalyse - mycotoxinen - analytische methoden - alternaria - food safety - food analysis - mycotoxins - analytical methods
    The objective of this research was: 1) adaptation of an existing LC-MS/MS method to determine 5 Alternaria toxins in various food commodities and 2) perform a survey (95 samples) to gain insight in the levels of Alternaria toxins in fresh apples, tomatoes, citrus, figs, olives, sunflower seeds, cereals, apple juices and tomato sauces, purchased in the Netherlands.
    Phytopathogenic Dothideomycetes
    Crous, P.W. ; Verkley, G.J.M. ; Groenewald, J.Z. - \ 2013
    Utrecht, The Netherlands : CBS-KNAW Fungal Biodiversity Centre (Studies in mycology 75) - ISBN 9789070351960 - 406
    dothideomycetes - plantenziekteverwekkende schimmels - taxonomie - fylogenie - gastheerreeks - alternaria - cercospora - phoma - pseudocercospora - septoria - nieuwe soorten - nieuw geslacht - dothideomycetes - plant pathogenic fungi - taxonomy - phylogeny - host range - alternaria - cercospora - phoma - pseudocercospora - septoria - new species - new genus
    This volume of Studies in Mycology is dedicated to the plant health officers of the world, who are constantly confronted by a range of plant pathogenic fungi that cause devastating diseases of agricultural and forestry crops. Five main groups of fungi are dealt with, namely Alternaria, Cercospora, Phoma, Pseudocercospora and Septoria. In the first paper Phoma sections Plenodomus, Heterospora and Pilosa were reinvestigated, resulting in the introduction of several novel genera and species. The second paper deals with the paraphyletic genus Pseudocercospora; host specificity was considered for 146 species of Pseudocercospora occurring on 115 host genera from 33 countries. From these results we concluded that the application of European and American names to Asian taxa, and vice versa, was often not warranted. The third paper deals with the genus Cercospora, which contains more than 5 000 different species. Isolates used in the molecular phylogeny were obtained from 161 host species, 49 host families and 39 countries. Although some species were found to host-specific, others were isolated from a wide host range. The fourth paper deals with phylogenetic lineages within the genus Alternaria, which was revealed to represent a well-supported node containing 24 internal clades and six monotypic lineages. Several genera were placed in synonymy with Alternaria, for which 16 new sections were proposed. Two papers deal with the genus Septoria, which was shown to be poly- and paraphyletic, leading to the introduction of 15 new genera, and more than 40 new species. Although some species were shown to be highly specific, other taxa were revealed to occur on hosts in more than six different plant families. For all taxa investigated multi-gene DNA data were deposited in GenBank and other databases to expedite future identification of these plant pathogenic fungi. No single locus was found to be the ideal DNA barcode gene for these taxa, and species identification will have to be based on a combination of gene loci and morphological characters.
    Bladval Golden eindelijk te tackelen (interview met Marcel Wenneker)
    Houweling, P. van; Wenneker, M. - \ 2011
    Nieuwe oogst / Magazine gewas 7 (2011)17. - ISSN 1871-093X - p. 10 - 11.
    alternaria - appels - plantenziekteverwekkende schimmels - fruitteelt - bladval - gewasbescherming - alternaria - apples - plant pathogenic fungi - fruit growing - leaf fall - plant protection
    Golden Delicious heeft in de zomer vaak last van veel bladval. Tientallen jaren zochten onderzoekers en telers naar oplossingen, maar zonder succes. Marcel Wenneker van PPO Randwijk ontdekte in de zomer van 2011 dat een bespuiting tegen de schimmelziekte alternaria uitstekend werkt tegen bladval.
    Ziek en Zeer : Verschillende soorten Alternaria veroorzaken bladvlekkenziekte in Zantedeschia
    Vink, P. - \ 2011
    BloembollenVisie 2011 (2011)223. - ISSN 1571-5558 - p. 21 - 21.
    zantedeschia - bloembollen - alternaria - schimmelziekten - bladvlekkenziekte - afwijkingen, planten - zantedeschia - ornamental bulbs - alternaria - fungal diseases - leaf spotting - plant disorders
    In dit artikel over het voortgezet diagnostisch onderzoek bij PPO dit keer een verslag van het basisonderzoek naar een bladvlekkenziekte in Zantedeschia. Daaruit is bekend geworden dat verscheidene Alternariasoorten in het gewas Zantedeschia zijn aangetroffen.
    Alternaria bladvlekkenziekte in bolgewassen
    Vink, P. - \ 2010
    PPO Bloembollen en Bomen - 13
    bladvlekkenziekte - alternaria - vuur (plantenziektekundig) - schimmelziekten - tulipa - tulpen - dahlia - lilium - lelies - diagnostische technieken - landbouwkundig onderzoek - teelt - gewasbescherming - nederland - leaf spotting - alternaria - blight - fungal diseases - tulipa - tulips - dahlia - lilium - lilies - diagnostic techniques - agricultural research - cultivation - plant protection - netherlands
    Bij de teelt van tulp, Dahlia en lelie komen de laatste jaren steeds vaker (in seizoen 2008 zelfs frequent) problemen voor van een plotseling optredende bladvlekkenziekte die er anders uitziet dan het bekende “vuur” veroorzaakt door de schimmel Botryis. Tot nu toe zijn daarbij steeds een keur aan gewasbeschermingsmiddelen ingezet om de aantasting te stoppen zonder dat bekend was tegen welk pathogeen de bestrijding gericht moest zijn. Vanuit bolgewassen met afwijkende bladvlekken zijn daarom bij Diagnostiekservice van PPO regelmatig isolaties gemaakt uit tulp, Dahlia en lelie waarbij regelmatig de schimmel Alternaia werd gevonden. Na determinatie bleek het steeds om de schimmel Alternaria alternata te gaan die ook bij het gewas Zantedeschia kan zorgen voor een bladvlekkenziekte te velde. Toch is vanuit praktijkervaring en onderzoek niet bekend of de schimmel Alternaia ook werkelijk primair in staat is om blad van tulp, Dahlia en lelie aan te tasten. Daarom is in het kader van het Voortgezet Diagnostisch Onderzoek geprobeerd om middels infectieproeven aan te tonen of de schimmel Alternaria alternaa ook werkelijk pathogeen is voor tulp, Dahlia en lelie en in staat is om bladvlekken in deze gewassen te veroorzaken.
    Alternaria in aardappel: een Europees alternatief
    Schepers, H.T.A.M. ; Evenhuis, A. - \ 2010
    Kennisakker.nl 2010 (2010)26-7.
    alternaria - geïntegreerde bestrijding - fungiciden - alternaria solani - alternaria alternata - aardappelen - symptomen - levenscyclus - beslissingsondersteunende systemen - akkerbouw - integrated control - fungicides - potatoes - symptoms - life cycle - decision support systems - arable farming
    Vroeger kwam Alternaria in Nederland op beperkte schaal voor, tegenwoordig komt Alternaria algemeen voor en kan het in sommige rassen en jaren flink schade veroorzaken. In dit artikel wordt daarom ingegaan op verschillende aspecten van Alternaria in aardappel: symptomen, factoren die aantasting beïnvloeden en beheersing en bestrijding van deze ziekte.
    Alternaria dauci in peen, projectjaar 2000
    Plentinger, M.C. ; Wanten, P.J. ; Schepers, H.T.A.M. - \ 2010
    Lelystad : Praktijkonderzoek voor de Akkerbouw en de Vollegrondsgroenten - 59
    groenteteelt - veldgewassen - daucus carota - gewasbescherming - schimmelziekten - chemische bestrijding - fungiciden - alternaria - proeven op proefstations - vegetable growing - field crops - daucus carota - plant protection - fungal diseases - chemical control - fungicides - alternaria - station tests
    In het jaar 2001 werden twee veldproeven uitgevoerd waarin fungiciden werden beproefd tegen Alternaria dauci in peen. De proefvelden werden op het PPO-AGV in Lelystad en in Meterik aangelegd. Het doel van het project was na te gaan of fungiciden die toegelaten zijn in andere gewassen of nog niet in Nederland zijn toegelaten, werkzaam zijn tegen Alternaria dauci in peen. Gewascontrole vond plaats door planten te beoordelen op een bladaantasting door Alternaria dauci. De aantasting werd regelmatig beoordeeld aan de hand van een ziekte-index. In dit tweede proefjaar werd gekeken naar de effectiviteit van de middelen op Alternaria en werden geen opbrengstgegevens verzameld.
    Pathogenicity of Stemphylium vesicarium from different hosts causing brown spot in pear
    Köhl, J. ; Groenenboom-de Haas, B.H. ; Goossen-van de Geijn, H.M. ; Speksnijder, A.G.C.L. ; Kastelein, P. ; Hoog, S. de; Ende, B.G. van den - \ 2009
    European Journal of Plant Pathology 124 (2009)1. - ISSN 0929-1873 - p. 151 - 162.
    pleospora-allii - causal agent - leaf-spot - disease - alternaria - california - infection - botryosum - inoculum - alfalfa
    Stemphylium vesicarium (teleomorph: Pleospora herbarum) is the causal agent of brown spot disease in pear. The species is also able to cause disease in asparagus, onion and other crops. Saprophytic growth of the fungus on plant debris is common. The objective of this study was to investigate whether isolates of S. vesicarium from different hosts can be pathogenic to pear. More than hundred isolates of Stemphylium spp. were obtained from infected pear fruits, dead pear leaves, dead grass leaves present in pear orchard lawns as well as from necrotic leaf parts of asparagus and onion. Only isolates originating from pear orchards, including isolates from dead grass leaves, were pathogenic on pear leaves or fruits in bioassays. Non-pathogenic isolates were also present in pear orchards. Stemphylium vesicarium from asparagus or onion, with one exception, were not pathogenic to pear. Analysis of the genetic variation between isolates using Amplified Fragment Length Polymorphism (AFLP) showed significant concordance with host plants. Isolates from asparagus or onion belonged to clusters separate from the cluster with isolates from pear or grass leaves collected in pear orchards. Multilocus sequencing of a subset of isolates showed that such isolates were similar to S. vesicarium.
    Voorkomen van Alternaria in de zaaizaadproductie van kool
    Köhl, J. ; Tongeren, C.A.M. van; Groenenboom-de Haas, L. ; Kastelein, P. ; Driessen, R. ; Heijden, L. van der - \ 2009
    biologische landbouw - vermeerderingsmateriaal - zaadproductie - koolsoorten - brassica - alternaria - gewasbescherming - biologische plantenveredeling - organic farming - propagation materials - seed production - cabbages - brassica - alternaria - plant protection - organic plant breeding
    Poster met onderzoeksinformatie naar effecten van bestrijdingsmiddelen tegen Alternaria beschikbaar voor de biologische teelt van bloemkolen
    Effectieve bestrijding combineren met lage milieubelasting
    Spruijt, J. ; Schepers, H.T.A.M. ; Evenhuis, A. ; Spits, H.G. - \ 2009
    phytophthora infestans - ziektebestrijding - aardappelen - fungiciden - dosering - alternaria - phytophthora infestans - disease control - potatoes - fungicides - dosage - alternaria
    Poster met informatie uit onderzoek naar de beste spuitstrategie voor de bestrijding van Phytophthora én Alternaria in de teelt van zetmeel-, poot-, en consumptieaardappelen
    Examples of breeding research for organic farming in the Netherlands
    Osman, A.M. - \ 2008
    alternaria - carrots - allium - cabbages - fusarium - mycotoxins - wheat - resistance breeding - organic plant breeding
    Kwaliteit van zaaizaad kool verbeteren
    Groot, S.P.C. - \ 2008
    BioKennis bericht Akkerbouw & vollegrondsgroenten 12 (2008).
    biologische landbouw - akkerbouw - vermeerderingsmateriaal - zaadproductie - koolsoorten - oogsttijdstip - rijpheid - ziektebestrijding - plantenpigmenten - zaadkieming - fusarium - alternaria - vollegrondsteelt - biologische zaden - organic farming - arable farming - propagation materials - seed production - cabbages - harvesting date - maturity - disease control - plant pigments - seed germination - fusarium - alternaria - outdoor cropping - organic seeds
    Kwalitatief goed biologisch zaaizaad voor koolsoorten is moeilijk te produceren. Oorzaken zijn de ongelijkmatige bloei en afrijping van het zaad. Daarnaast kunnen schimmels en bacteriën via het zaad de plant besmetten. In dit biokennis bericht informatie over onderzoek aan apparatuur die het optimale oogsttijdstip bepaalt of de zieke zaden eruit selecteert.
    Beheersing dode bloemknoppen bij peer binnen bereik
    Wenneker, M. ; Anbergen, R.H.N. ; Joosten, N.N. - \ 2008
    De Fruitteelt 98 (2008)19. - ISSN 0016-2302 - p. 9 - 9.
    boomgaarden - fruitteelt - fruitgewassen - peren - alternaria - deuteromycotina - plantenziekteverwekkende schimmels - bestrijdingsmethoden - spuiten - gewasbescherming - toelating van bestrijdingsmiddelen - orchards - fruit growing - fruit crops - pears - plant pathogenic fungi - control methods - spraying - plant protection - authorisation of pesticides
    Uit PPO-onderzoek blijkt dat Alternaria de primaire veroorzaker is van dode bloemknoppen bij peer. De mate van aantasting verschilt per perceel en per jaar. Met de toelating van Switch is een directe bestrijding van Alternaria mogelijk geworden
    Alternaria in het voetspoor van Phytophthora
    Schepers, H.T.A.M. - \ 2007
    Aardappelwereld 61 (2007)4. - ISSN 0169-653X - p. 23 - 25.
    aardappelen - alternaria - alternaria alternata - plantenziekteverwekkende schimmels - potatoes - plant pathogenic fungi
    Alternaria is een schimmelziekte die in opkomst is, zo bleek tijdens het Syngenta Alternaria symposium. De laatste jaren zijn de omstandigheden waaronder deze schimmel kan groeien verbeterd. Ingegaan wordt op de mogelijkheden om deze schimmel te bestrijden
    Vóór de bloei spuiten heeft geen zin (Alternaria in aardappel) (Interview)
    Schepers, H.T.A.M. - \ 2007
    Boerderij/Akkerbouw 92 (2007)5. - ISSN 0169-0116 - p. 19 - 19.
    alternaria - aardappelen - solanum tuberosum - spuiten - gewasbescherming - plantenziekteverwekkende schimmels - fungiciden - alternaria - potatoes - solanum tuberosum - spraying - plant protection - plant pathogenic fungi - fungicides
    Het algemene spuitadvies luidt: spuit tegen Alternaria ná de bloei. Praktijkonderzoek Plant & Omgeving (PPO) onderzocht of dit advies nog steeds opgaat. Voor de bloei starten met mancozeb tegen Alternaria heeft geen effect, blijkt uit dit onderzoek
    Alternariasporen zijn altijd aanwezig. (Interview)
    Schepers, H.T.A.M. - \ 2007
    Nieuwe oogst / Magazine gewas 3 (2007)5. - ISSN 1871-093X - p. 14 - 15.
    alternaria solani - alternaria - plantenziekteverwekkende schimmels - aardappelen - pootaardappelen - fungiciden - schimmelbestrijding - gewasbescherming - plant pathogenic fungi - potatoes - seed potatoes - fungicides - fungus control - plant protection
    Alternaria solani is samen met phytophthora wereldwijd een vaste begeleider van de aardappel. Beide ziektes infecteren het gewas na een bladnatperiode van vier tot zes uur. Alternaria solani tast, net als phytophthora, loof en knol aan. Alternaria solani veroorzaakt grote vlekken op blad en knol. Het kan een vatbaar gewas bij gunstige omstandigheden ernstig aantasten
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