Biografi

Arbeidsområde:
Ledelse og administrasjon av Divisjon for bioteknologi og plantehelse
 
Tidligere arbeidsområde:
Forskning innen soppsjukdommer i grønnsaker og potet: diagnostikk, biologi og bekjempelse
 

Les mer

Sammendrag

Avslutningsseminar for prosjektet: Improved quality of Norwegian fruits, potatoes and vegetables after long- and short-term storage (2010-2014).

Sammendrag

Initial sources of inoculum of Phytophthora infestans were investigated in ten potato fields with early outbreaks of potato late blight. Infected plant samples and isolates from these fields were examined with respect to mating type prevalence, fungicide resistance and genotypes based on microsatellites A high proportion (91 %) of the isolates recovered were of mating type A1. However, both mating types were found in 3 of 9 fields with more than one isolate recovered, and sometimes both mating types were found on the same plant. Most of the isolates recovered from fields treated with metalaxyl-M prior to sampling had reduced sensitivity or were resistant to metalaxyl-M, and most of the isolates recovered form fields without metalaxyl treatment were sensitive. The isolates recovered from fields treated with propamocarb prior to sampling had a higher frequency of reduced sensitivity to propamocarb than isolates from fields without propamocarb treatment. We found that most plants contained more than one P. infestans SSR-genotype. Clustering analysis of the infected samples revealed that most samples clustered together according to fields. By combining information from P. infestans isolates and DNA extracts from the leaf lesions we found examples of both mating type A1 and A2 having the same multilocus genotype. This result indicates that both of these genotypes have a common ancestor, hence the inoculum originates from oospores. Although this a minor study of only 10 fields with a limited amount of isolates and plant samples, the results indicate oospores in the soil is an inoculum source. Hence the forecasting model to predict outbreaks of potato late blight should be modified to include this.       

Til dokument

Sammendrag

Specific PCR primers were developed for identifying two post harvest pathogens, Mycocentrospora acerina and Fibularhizoctonia carotae, which cause liquorice rot and crater rot respectively, during prolonged low temperature storage of carrots. The methods allow routine detection of less than 0.3 pg of M. acerina DNA and less than 0.03 pg F. carotae DNA, even in the presence of large excess of plant or soil DNA. Standard PCR and quantitative PCR gave similar results and either method could be used in a practical situation.  Experiments were carried out testing these methods on different types of carrot tissue- and soil- samples. Soil was sampled before sowing, and soil adhering to the roots or root tissue was sampled at different times during the growing season or at harvest. Soil adhering to the carrots at harvest had the best predictive ability for liquorice rot development during storage (R2predicted 74.9 % using standard PCR), but samples taken during the growing season also gave reasonably good predictive ability values.  PCR data from soil samples taken in the spring were not as good as a predictor for thisdisease. A dense sampling strategy using 20 m between sampling points generally gave better orrelation between PCR data and disease data than using 40 m between the sampling points.  Use of the developed methods in an IPM strategy for liquorice rot is discussed. For crater rot the correlation between PCR data and disease data was generally poor for all types of samples. These results are discussed in relation to the biology of F.carotae.  

Sammendrag

Downy mildew, caused by Hyaloperonospora parasitica s.l., represents an increasing threat to Norwegian production of cruciferous vegetable crops. Although the pathogen has been present in Norway for over a century, the intensified production regimes of field vegetables has contributed to an increase in disease incidence and severity. The project “Effective and sustainable control strategies for downy mildew in rocket, broccoli and cauliflower” were initiated by vegetable growers and financed by the Norwegian Research Council, “Jordbruksavtalen”, “Fondet” and vegetable growers for the period 2009-2011. As part of the project we have surveyed the presence of downy mildew in cruciferous crops and weeds, tested possible cross inoculation between different cruciferous crops and weeds, and tested how long detached spores can survive in air.   The survey of downy mildew incidence in cruciferous crops (mainly rocket, broccoli and cauliflower) and weeds were performed by local extension officers in the Counties Buskerud, Rogaland, Vestfold, østfold, and Hedmark. In addition, 65 growers were asked to survey and report findings in their fields. During the project period downy mildew incidence was mainly observed in wild rocket (Diplotaxis tenuifolia) and broccoli, while a few incidences of downy mildew were reported in swede, oil seed rape and the weed Sheperd’s purse (Capsella bursa-pastoris). The host range of isolates collected in the survey was assessed on a selection of cruciferous species.  Seedlings of wild rocket (‘DI902’), cultivated rocket (Eruca sativa), cauliflower (‘Freedom’), broccoli (‘Ironman’), oil seed rape (‘Valo’) and swede (‘Vige’) were inoculated by spraying the cotyledons with a spore suspension. One week after inoculation, the seedlings were incubated over-night at high RH and scored for positive infections by observation of visible sporulation on the cotyledons. Preliminary results show that downy mildew from oil seed rape can infect swede, cauliflower and broccoli. Isolates from broccoli were partly virulent on cauliflower. An isolate from swede were virulent on broccoli, while an isolate from rape were virulent on cauliflower, broccoli and swede. An isolate from Sheperd’s purse was virulent on broccoli. Isolates from wild rocket were not virulent on any of the other plants in the trial. The results indicate a risk of cross infection between different cruciferous species, although also supporting the ongoing discussions on dividing H. parasitica into separate species. The possibility of long distance dispersal of viable spores depends on how long the spores can survive in free air. Spores from freshly sporulating rocket seedlings were transferred to filter paper and exposed to solar radiation or in shade. Preliminary results show that spores were not able to germinate after 6 hours exposure to the sun, while shaded spores were able to survive for 24 hours or more. These results will be included in the development of a forecasting model for downy mildew on cruciferous crops.  

Sammendrag

The effects of soil conditions and cultural control methods on development of skin blemish diseases were studied in three different field experiments dur­ing two years. All studies included the cultivars Satur­na and/or Asterix. Experiment 1 included effects of fertilizers and soil compaction, mainly on Streptomyces ssp (common scab), while experiment 2 studied effects of soil humidity on various skin blemish diseases. Experiment 3 studied effects of harvest, curing and storage strategies on silver scurf (Helminthosporium solani), but also on powdery scab and black scurf.

Sammendrag

Bioforsk had the pleasure of hosting the Nordic Baltic Potato Tuber-Disease Workshop 2011 (PTDW 2011) at Hamar, Norway 16-18 November 2011. The workshop was mainly aimed at potato advisors, including the potato industry, and scientists from the Nordic and Baltic countries. In addition, we also had participants that are plant breeders, students, and and other people interested in potato quality. In totalthere were about 60 participants at the workshop from the Nordic countries, UK, Switzerland, USA and China. This Workshop was an activity in Bioforsk project: “Improved potato quality by reduced skin blemishdiseases (scab and scurf) in Norwegian potato production” (2008-2012). This project was financed by grants from the Research Council of Norway, the Foundation for Research Levy on Agricultural Products, the Agricultural Agreement Research Fund, and Norwegian potato growers and food industries; Gartnerhallen, Bama, ICA-Norge, NF-Grønt, KiMs and Maarud. The foreign experts attached to this project, Alison Lees (UK), Leslie Wanner (USA) and Jari Valkonen(Finland), were contributors in the workshop. In addition invited speakers were Lv Dianqiu from Chinaand Ueli Merz from Switzerland. The workshop had 5 different sections, in which the 3 first had presentations from the project:1. Occurrence of skin blemish diseases in the Nordic and Baltic countries2. Diagnosis and biology of different skin blemish pathogens3. Control of skin blemish diseases4. Research activities on other potato tuber diseases in Nordic and Baltic countries5. Future challenges In the table of contents, the abstracts are presented in the same order as found in the program. The scientific workshop committee consisted of Jari Valkonen (Finland), Björn Andersson (Sweden), BentJ. Nielsen (Denmark) and Arne Hermansen (Norway).

Sammendrag

Norwegian onion growers have in recent years complained about bacteria like disease problems of bulb onion, Allium cepa L., both in the field and in storage.  In order to find out which bacteria that are involved in theses rotting symptoms, a small survey was carried out on diseased onions from different parts of the country. Biochemical- and pathogenicity tests and fatty acid profiling showed that there was a lot of different bacteria present in the diseased onions. Many of them were ordinary water- and soil residents, which are not known to cause diseases of onion, such as Enterococcus, Salmonella, Cedecea, Stenotrophomonas, Chryseobacteruim and Curtobacterium. But there were also bacteria present which are known to cause diseases of onion in other countries, such as Burkholderia gladioli pv alliicola, Pseudomonas viridiflava, Enterobacter chloacae and Pantoea agglomerans. This is the first report of Burkholderia gladioli pv alliicola in Norway.

Sammendrag

Gjennom prosjektet "Sikker og miljøvennlig bekjempelse av bladskimmel i løk, salat og agurk i Norge" har vi i perioden 2006 til 2009 hatt som hovedmål å få til effektiv og miljøvennlig bekjempelse av bladskimmel ved å utvikle varslingsstrategier for disse sjukdommene.  Prosjektet har vært finansiert av Norges forskningsråd, Fondet for forskningsavgift på landbruksprodukter, Forskningsmidler over Jordbruksavtalen og dyrkermiljøene for isbergsalat, vårløk, kepaløk og frilandsagurk. Forekomst av bladskimmel er vanskelig å forutse og varierer fra år til år, både i utbredelse og tidspunkt for når angrepene oppstår. Problemene med bladskimmel er størst på ettersommeren og vanligst forekommende i områder med intensiv produksjon. Relativt små angrep av bladskimmel kan medføre store tap i kulturer hvor bladene utgjør en viktig del av avlingen, som i salat og vårløk.  I agurk og kepaløk kan angrep av bladskimmel medføre at bladene visner, og dermed føre til store avlingstap.  Bladskimmel forårsakes av sopplignende organismer som er svært vertsspesifikke og sjelden smitter mellom ulike plantefamilier. Alle arter av bladskimmel produserer ukjønna sporer som spres i lufta. Vi har vist i forsøk at sporer fra salat- og agurkbladskimmel har ulik evne til å overleve i luft. Etter tre timers eksponering i sol var alle sporene fra salatbladskimmel drept, mens sporene kunne overleve ca ett døgn i skygge. Sporer fra agurkbladskimmel overlevde ca ett døgn i sol, mens sporene kunne overleve i flere døgn i skyggen. Det er derfor sannsynlig at levedyktige sporer av agurkbladskimmel kan spres i luft over lange avstander. De fleste arter av bladskimmel kan også danne hvilesporer som kan overleve flere år i jorda. Slike hvilesporer har trolig liten betydning som smittekilde for agurkbladskimmel i Norge, mens det er mer usikkert hvor viktig dette er i løk. I salat anses hvilesporer å være av større betydning. Vekstskifte bør derfor utgjøre en viktig del av bekjempelsesstrategien mot bladskimmel. Bladskimmel har en svært god tilpasningsevne både når det gjelder å bryte resistens i vertplanter og ved å utvikle resistens mot kjemiske preparater. Det vil derfor være viktig å begrense angrep av bladskimmel samtidig som unødvendig bruk av kjemiske preparater unngås. En rekke feltforsøk med utprøving av fungicider mot bladskimmel er gjennomført av Norsk landbruksrådgiving hos lokale produsenter, og flere av de prøvde midlene hadde god effekt mot bladskimmel i salat, vårløk og agurk. Det er imidlertid påvist en tydelig tendens til redusert effekt av Aliette 80 WG og det plantestyrkende preparatet Resistim i enkelte isolater av salatbladskimmel, noe som indikerer at resistensproblemer er i ferd med å oppstå. Flere varslingsmodeller for salatbladskimmel og løkbladskimmel er testet i prosjektperioden, og to modeller er nå tilgjengelige i VIPS (http://www.vips-landbruk.no/).  Varsling av bladskimmel er basert på å forutse perioder med klimatiske forhold som er gunstige for sporulering og infeksjon av patogenet. Varslingsmodellene kan brukes til å vurdere når en bør intensivere overvåking av felt med hensyn på angrep av bladskimmel, og til å bestemme når og hvor ofte det vil være behov for å sprøyte mot bladskimmel. For agurkbladskimmel finnes det ikke noen aktuell modell, men for denne sjukdommen vil overvåkning av når smitten først kommer inn i et område med agurkproduksjon være mer hensiktsmessig enn å bruke en varslingsmodell til å vurdere sprøytetidspunkt. Ved bruk av sporefeller som suger inn luft kan eventuell luftbåren smitte fanges og identifiseres ved bruk av PCR.  I flere tilfeller har det lykkes å påvise DNA fra agurkbladskimmel i sporefellene før sjukdommen ble påvist i felt.  

Sammendrag

Kartlegging av hvilke arter av Streptomyces som forårsaker flatskurv i potet i Norge er et av målene i "skurvprosjektet" ved Bioforsk Plantehelse. Så langt har Streptomyces scabies/ Streptomyces europaeiscabiei og Streptomyces turgidiscabies blitt isolert fra om lag 200 prøver fra 13 fylker i Norge.

Sammendrag

Bakteriell råte i kepaløk har de siste årene økt i omfang uten at man vet hvilke bakterier som er årsak til skadene. For å skaffe et kunnskapsgrunnlag for problemstillingen ble det utført en kartlegging av bakterier som forekommer i løk med råtesymptomer.

Sammendrag

En forbedret tørråtevarslingsmodell er utviklet basert på forsøk med sporefelle og fangstplanter. Modellen beregner risikoen for sporeproduksjon med påfølgende sporespredning, overlevelse og infeksjon ut fra klimadata på timebasis, forutsatt at det er tørråtesmitte i området.

Sammendrag

Skadedyr, ugras og sopper som er blitt resistente mot plantevernmidler er blitt et stadig økende problem i flere viktige jord- og hagebruksvekster de siste årene. Hvordan kan vi snu denne utviklingen?

Sammendrag

In 1996, a survey on cavity spot started in Norway. Among the Pythium species isolated from the lesions a pathogenic Pythium was found that could not be identified neither by morphological nor by molecular methods (ITS sequencing). This Pythium sp. was repeatedly detected using specific primers developed for this propose and in many cases isolated from cavity spots lesions. The isolates from the new species do not produce zoospores. Oogonia are smooth walled and mostly intercalary with an average size about 20µm. Oospores are aplerotic with an average diameter approximately 17 µm and wall less then 2 µm thick. Antheridia are mostly monoclinous with a sort stalk or sessil, but diclinous antheridia are also common. The modal number of antheridia per oogonium is one or two. Some differences are observed between the isolates studied. Some isolates have a daily growth rate of ca 23 mm on PCA at 25 °C while others have a growth rate around 28 mm. The isolates that grow slower have a tendency to produce one antheridium per oogonium while the isolates with higher growth rates normally produce two. These two groups could also be differentiated based on their ITS sequences which showed 97.8% identity in the 955 base pair rDNA fragment. By using the developed PCR primers it is possible to detect isolates that do not produce the sexual stage in single cultures. These isolates have the same ITS sequence and a similar growth rate and pattern than the fast growing fertile ones.

Sammendrag

Late blight forcasting in VIPS i s presented. Validation trials have show acceptable results regarding late blight control

Sammendrag

A new potato late blight forecasting model based on hourly weather date is developed based on trials with spore traps and trap plants. The model is built up of sub models for for the different steps in the epidemiological cycle, spore production, release, survival and infection. Long humid periods are suitable for spore production, at moderate humidity the process goes slower. The amount of viable attached sporangia is reduced by drought, and some spores are washed off during rain. Spores are released into the air by a drop in humidity or increased radiation, but the release is inhibited at high leaf wetness. The amount of viable released spores is strongly inhibited by solar radiation. The spore load is also reduced by precipitation and by germination. The leaf wetness duration have to sufficient for the spores to germinate and infect. The risk of blight development is a function of the amount of viable released spores and the duration of leaf wetness.

Sammendrag

Downy mildews represent some of the most important plant diseases in the production of several field vegetable crops in Norway. Disease outbreaks are difficult to predict since severity of the diseases and the first appearance of the pathogens can differ substantially between seasons. As part of an ongoing project, the initial sources of inoculum for downy mildews of onion (Peronospora destructor), lettuce (Bremia lactucae) and cucumber (Pseudoperonospora cubensis) is investigated to ensure the use of appropriate control measures for these diseases in Norway. Necrotic leaf tissue from infected plants has been examined for the presence of oospores. Oospores have so far been found profusely in lettuce and sparsely in onion, but not in cucumber. Other aspects that are surveyed are the distribution of spores in air. Spore traps are used to identify both the initial appearance of inoculum, and the presence and amount of spores over a field. To determine spore quantities, real-time PCR has been applied to analyze daily spore catch. These results were compared to data from parallel spore traps where hourly numbers of spores are enumerated by use of microscope. An attempt to backtrack an early infection of P. cubensis was made by producing trajectories to show where possible sources of infection may be located in the case of long distance distribution of spores by air. This work will be continued in 2008 and 2009, and the results will be used for better forecasting of downy mildew pathogens in Norway.

Sammendrag

Bladskimmel utgjør noen av de viktigste plantesjukdommene i norske frilandsgrønnsaker. Sjukdomsutbrudd er vanskelige å forutse siden angrepsgrad og tidspunkt for første funn av patogenene kan variere fra sesong til sesong. Som del av et pågående prosjekt har smittekilder for bladskimmel i løk (Peronospora destructor), salat (Bremia lactucae) og agurk (Pseudoperonospora cubensis) blitt undersøkt for å sikre at riktige tiltak for kontroll gjennomføres. Forekomst av oosporer i blad og fordeling av sporer i luft har vært undersøkt. Dette arbeidet fortsettes i 2008 og 2009, og resultatene skal brukes til utvikling av bedre varsling av bladskimmelpatogener i Norge.

Sammendrag

Downy mildews represent some of the most important plant diseases in the production of several field vegetable crops in Norway. Disease outbreaks are difficult to predict since severity of the diseases and the first appearance of the pathogens can differ substantially between seasons. As part of an ongoing project, the initial sources of inoculum for downy mildews of onion (Peronospora destructor), lettuce (Bremia lactucae) and cucumber (Pseudoperonospora cubensis) is investigated to ensure the use of appropriate control measures for these diseases in Norway. Necrotic leaf tissue from infected plants has been examined for the presence of oospores. Oospores have so far been found profusely in lettuce and sparsely in onion, but not in cucumber. Other aspects that are surveyed are the distribution of spores in air. Spore traps are used to identify both the initial appearance of inoculum, and the presence and amount of spores over a field. To determine spore quantities, real-time PCR has been applied to analyze daily spore catch. These results were compared to data from parallel spore traps where hourly numbers of spores are enumerated by use of microscope. An attempt to backtrack an early infection of P. cubensis was made by producing trajectories to show where possible sources of infection may be located in the case of long distance distribution of spores by air. This work will be continued in 2008 and 2009, and the results will be used for better forecasting of downy mildew pathogens in Norway.

Sammendrag

Sykdommen klumprot ble beskrevet som et problem allerede på 1200-tallet i Europa, og den er fortsatt et stort problem ved dyrking av korsblomstra vekster over hele verden. Årsak til sykdommen er parasitten Plasmodiophora brassicae som tidligere ble regnet som en sopp, men som etter nyere analysemetoder er definert til rike Protozoa. Parasitten angriper røttene på de fleste arter i korsblomstfamilien, både grønnsaker, prydplanter og viltvoksende planter inkludert en del ugras. Angrepet kan i enkelte tilfeller føre til tap av hele avlinger, og parasitten er meget vanskelig å bli kvitt hvis man først har fått den inn i hagen.

Sammendrag

Kålbladskimmel, forårsaket av Hyaloperonospora parasitica (Pers.) Constant., er utbredt i alle deler av verden hvor det dyrkes kålplanter. De første symptomene på kålbladskimmel viser seg vanligvis først på blader og blomsterstander, men alle overjordiske deler av planten kan bli infisert. Frøplanter vil lettere dø som resultat av en infeksjon enn eldre planter. Effekten av patogenet på senere vekststadier er generelt ikke så alvorlig, men kan medføre svekket kvalitet eller redusert avling. Kålbladskimmel er vanlig forekommende på en lang rekke kultur-, ugress- og prydplanter innen korsblomstfamilien (Brassicaceae), men det er noe uklart hvor stor vertsspesialiering patogenet har innen de ulike slekter og arter. Bladskimmelinfeksjoner er polysykliske og danner mange generasjoner med ukjønna konidiesporer i løpet av en sesong. I tillegg kan kålbladskimmel danne hvilesporer (oosporer) som bidrar til at patogenet kan overleve lenge i jord. Hvert trinn i livssyklusen, for eksempel sporespiring, infeksjon, latenstid og sporulering påvirkes av klimatiske forhold. En generell tommelfingerregel for kålbladskimmel er at sjukdommen er mest problematisk i felt ved temperaturer mellom 10 og 15 °C og høy luftfuktighet. Sporulering skjer hovedsakelig om natta og sporene slippes om morgenen når tørkende konidioforer vrir seg kraftig og slynger konidier ut i lufta. De første symptomene på kålbladskimmel kan være synlige allerede 3 til 4 døgn etter infeksjon av konidiene. Konidier av H. parasitica spres med vind og vannsprut lokalt i åkeren og mellom felt som ligger i samme dyrkingsområde. Det er også mulig at konidiene kan fraktes over lengre avstander med luftstrømmer i atmosfæren, men det er uklart hvor langt konidier av H. parasitica kan transporteres og fremdeles være spiredyktige. Dersom oosporer dannes kan disse overleve i planterester og i jord og opptre som primær smittekilde. Kålbladskimmel kan overvintre i vinterettårige, toårige eller flerårige korsblomstra vertplanter. Det er imidlertid noe uklart hvor stor betydning slike vertplanter har som smittekilde for grønnsakvekster. Forebyggende bekjempelse av kålbladskimmel innebærer fjerning av planterester, vekstskifte med ikke korsblomstra vekster og ugresskontroll for å begrense smittekilder lokalt. Systemer som varsler om klimaforhold som fremmer sporulering og infeksjon kan være et godt hjelpemiddel til å vurdere faren for utvikling av bladskimmel og finne riktig sprøytetidspunkt.

Sammendrag

Kålbladskimmel har de siste årene ført til problemer for dyrkere av korsblomstra grønnsaker, spesielt ruccola og brokkoli. I 2007 har det vært gjennomført et forprosjekt hvor en blant annet har kartlagt sjukdommen i sesongen, sett på effekten av ulike fungicider og gjennomført et litteraturstudium.

Sammendrag

Phytophthora infestans is an important pathogen on potato and tomato during the winter seasons in the north of Vietnam and all the year around in Lam Dong province in the south of Vietnam. Data from earlier studies of isolates of P. infestans collected in 2002-2003 showed that the P. infestans population on tomato and potato from Vietnam still consist of the "old" population. However preliminary studies of P. infestans samples from 2007 indicate that this situation has started to change. Data from aggressiveness tests of P. infestans isolates on tomato and potato showed that the majority of isolates collected from tomato could not infect potato. All tested isolates originating from potato infected both hosts. From 2005-2007, field experiments in tomato and potato using IPM strategies for controlling late blight have been carried out in Lam Dong province and in Hanoi area (north of Vietnam). In these experiments, cultivars with different levels of late blight resistance and different fungicide dosages have been tested. Simple forecasting methods and sanitation procedures were also included in some of the experiments. In Lam Dong, strategies including 7 days fixed spray intervals with full dose of the fungicide mancozeb did not control late blight properly in tomato, and all 4 tomato experiments were terminated early. In the potato experiments use of a more modern fungicide could control late blight using reduced dosages. In the tomato experiments in the north no natural infection of late blight occurred during the experimental period.

Sammendrag

Phytophthora infestans is an important pathogen on potato and tomato during the winter seasons in the north of Vietnam and all the year around in Lam Dong province in the south of Vietnam. Data from earlier studies of isolates of P. infestans collected in 2002-2003 showed that the P. infestans population on tomato and potato from Vietnam still consist of the "old" population. However preliminary studies of P. infestans samples from 2007 indicate that this situation has started to change. Data from aggressiveness tests of P. infestans isolates on tomato and potato showed that the majority of isolates collected from tomato could not infect potato. All tested isolates originating from potato infected both hosts. From 2005-2007, field experiments in tomato and potato using IPM strategies for controlling late blight have been carried out in Lam Dong province and in Hanoi area (north of Vietnam). In these experiments, cultivars with different levels of late blight resistance and different fungicide dosages have been tested. Simple forecasting methods and sanitation procedures were also included in some of the experiments. In Lam Dong, strategies including 7 days fixed spray intervals with full dose of the fungicide mancozeb did not control late blight properly in tomato, and all 4 tomato experiments were terminated early. In the potato experiments use of a more modern fungicide could control late blight using reduced dosages. In the tomato experiments in the north no natural infection of late blight occurred during the experimental period.

Sammendrag

A total of 743 single-lesion isolates of Phytophthora infestans were collected in summer 2003 from Denmark, Finland, Norway and Sweden. Most of the isolates were tested for mating type, snd subsets for sensitivity to fungicides and virulence (host specific pathogenicity). Approximately 60 % of the isolates were A1 mating type in each country. Both mating types were present in 40 % of the fields where more than one isolate was tested,indicating strong potential for sexual reproduction. The proportion of metalaxyl-resistant isolates dropped under 15 % from the 60% observed in the early 1990s in Norway and Finland, possibly due to lower selection pressure because of decreased use of metalaxyl. PropamocarbHCl sensitivity remained unchanged in the Nordic countries compared to the situation in 1997-2000 in Finland. Four isolates collected from Finland and Sweden were able to sporulate in the presence of this fungicide at a concentration of 1000 mg L-1. In Norway and Finland the frequencies of virulence factors and pathotypes remained nearly unchanged since 1990s, but the mean number of virulence factors per isolate increased from 5.6 to 6.3. In Denmark and Sweden virulence factors 2 and especially 6 were more common than in Norway and Finland. In addition, in the Swedish population the frequencies of pathotypes were quite even while in other countries pathotype 1.3.4.7.10.11 was most prevalent.

Sammendrag

Influence of weather conditions on sporangia production, release and infection of P. infestans was investigated in Denmark, Norway and Finland using Burkard spore traps and trap plants exposed in field plots. Results from field trials show that P. infestans normally forms its sporangia during humid periods at night and that they are released by a drop in the humidity in the morning. The infection can occur in the morning if there are dew drops remaining on the canopy while sporangia are being released. Sporangia released into the air can only infect if they make contact with free water from either dew or precipitation within very few hours. The studies also showed that the newly formed sporangia can remain in the lesions during overcast weather conditions and be dispersed over at least 2-3 days. By coupling the sporangia formation with a model of sporangia survival as affected by global radiation, a better correlation was achieved between infection on trap plants and dispersed sporangia than if only the index of sporangia formation was used as a predictor. The involvement of the survival model will reduce the number of false warnings, and thus reduce fungicide consumption.

Sammendrag

Influence of weather conditions on sporangia production, release and infection of P. infestans was investigated in Denmark, Norway and Finland using Burkard spore traps and trap plants exposed in field plots. Results from field trials show that P. infestans normally forms its sporangia during humid periods at night and that they are released by a drop in the humidity in the morning. The infection can occur in the morning if there are dew drops remaining on the canopy while sporangia are being released. Sporangia released into the air can only infect if they make contact with free water from either dew or precipitation within very few hours. The studies also showed that the newly formed sporangia can remain in the lesions during overcast weather conditions and be dispersed over at least 2-3 days. By coupling the sporangia formation with a model of sporangia survival as affected by global radiation, a better correlation was achieved between infection on trap plants and dispersed sporangia than if only the index of sporangia formation was used as a predictor. The involvement of the survival model will reduce the number of false warnings, and thus reduce fungicide consumption.

Sammendrag

Aerial dispersal of inoculum is critical to the spread of many plant diseases; including potato late blight (Phytophthora infestans (Pi)), lettuce downy mildew (Bremia lactucae (Bl)) and cucurbit downy mildew (Pseudoperonospora cubensis (Pc)). In addition to relative humidity and temperature, spore survival during aerial dispersal is affected by solar irradiation (SI), in particular during long-distance transport at higher altitudes. We evaluated the potential survival of spores in air by placing detached spores of Pi, Bl and Pc on filter paper in either direct sun or shade at time intervals from 0.5 to 3 h (Pi and Bl), or up to 42 hours (Pc). Thereafter, the filter papers were placed in moist chambers for 15 min prior to incubation on pea agar (Pi) or water agar (Bl and Pc) for 24 h, before the viable spores were enumerated. Spores were considered viable if they exhibited a germ tube or released zoospores. Preliminary results show that no spores of Pi, Bl and Pc germinated after 1, 3 and 30 h exposure to direct sun, with critical SI doses near 700, 2000 and 8500 Wm-2, respectively. In shade, no Pi spores germinated after 3 h, while spores of Bl and Pc were still viable after 3 and 42 h, respectively. In Norway, the potential for long distance distribution of Pi is restricted, but more likely for Bl and Pc. Further experiments will be conducted to find the maximum survival time for spores of these pathogens under Norwegian climatic conditions.

Sammendrag

The existing potato late blight forecast and decision support systems used in the Nordic countries are based on data from the 1930s and the 1950-60s on how temperature and humidity influence Phytophthora infestans epidemiology. Influence of weather conditions on sporangium production, release, viability and infection of P. infestans was investigated in Denmark, Norway and Finland using Burkard spore traps and exposure of trap plants in field plots in 2005-2007. Large amounts of sporangia were trapped after nights with long periods with high humidity. Sporangia produced in one humidity period were mainly released at the first humidity drop in the morning hours, but there were also some periods with delayed sporangium release. Local new infections occurred mainly during the morning hours when leaves were still wet. On many days sporangia did not survive until the afternoon and the results indicate that conditions for survival of sporangia and infection are major bottlenecks for the spread and development of the disease. These results have important implications for practice. Survival of sporangia and infection must be better integrated into the calculation of "risky days" in late blight forecasting systems.

Sammendrag

The existing potato late blight forecast and decision support systems used in the Nordic countries are based on data from the 1930s and the 1950-60s on how temperature and humidity influence Phytophthora infestans epidemiology. Influence of weather conditions on sporangium production, release, viability and infection of P. infestans was investigated in Denmark, Norway and Finland using Burkard spore traps and exposure of trap plants in field plots in 2005-2007. Large amounts of sporangia were trapped after nights with long periods with high humidity. Sporangia produced in one humidity period were mainly released at the first humidity drop in the morning hours, but there were also some periods with delayed sporangium release. Local new infections occurred mainly during the morning hours when leaves were still wet. On many days sporangia did not survive until the afternoon and the results indicate that conditions for survival of sporangia and infection are major bottlenecks for the spread and development of the disease. These results have important implications for practice. Survival of sporangia and infection must be better integrated into the calculation of "risky days" in late blight forecasting systems.

Sammendrag

Aerial dispersal of inoculum is critical to the spread of many plant diseases; including potato late blight (Phytophthora infestans (Pi)), lettuce downy mildew (Bremia lactucae (Bl)) and cucurbit downy mildew (Pseudoperonospora cubensis (Pc)). In addition to relative humidity and temperature, spore survival during aerial dispersal is affected by solar irradiation (SI), in particular during long-distance transport at higher altitudes. We evaluated the potential survival of spores in air by placing detached spores of Pi, Bl and Pc on filter paper in either direct sun or shade at time intervals from 0.5 to 3 h (Pi and Bl), or up to 42 hours (Pc). Thereafter, the filter papers were placed in moist chambers for 15 min prior to incubation on pea agar (Pi) or water agar (Bl and Pc) for 24 h, before the viable spores were enumerated. Spores were considered viable if they exhibited a germ tube or released zoospores. Preliminary results show that no spores of Pi, Bl and Pc germinated after 1, 3 and 30 h exposure to direct sun, with critical SI doses near 700, 2000 and 8500 Wm-2, respectively. In shade, no Pi spores germinated after 3 h, while spores of Bl and Pc were still viable after 3 and 42 h, respectively. In Norway, the potential for long distance distribution of Pi is restricted, but more likely for Bl and Pc. Further experiments will be conducted to find the maximum survival time for spores of these pathogens under Norwegian climatic conditions.

Sammendrag

Norge deltok i EU-prosjektet Blight-MOP i perioden 2001-2005 med mål å redusere tørråte i økologisk potetproduksjon uten bruk av kobberpreparat. Sluttrapporten ble ferdigstillt i 2007 og denne publikasjon er en oppsummering. Prosjektet har sett på tørråteproblemet fra flere hold og i et bredt systemperspektiv.

Sammendrag

A series of field trials combining cultivars with different levels of resistance to Phythophtora infestans and different haulm killing methods was conducted in 1997, 1998 and 1999 to assess the contamination potential of the haulm. In addition, the frequency of tubers with late blight was assessed after harvest and storage, combining effects of pretreatment infection, infection by the haulm at harvest and the development of the disease during storage. Haulm killing was performed by diquat (200, 400, 600 g a.i. ha-1), half cutting of the haulm in combination with diquat (100, 200, 300 g a.i. ha-1) or full cutting of the haulm. In those treatments where haulm killing was performed purely chemically the haulm remnants" contamination potential tended to increase at reduced doses. Full mechanical destruction gave as low a contamination potential as application of the full dose of chemical haulm killer. However, there were no consistent differences between the haulm killing treatments in the frequency of blighted tubers after harvest and storage. This indicates that the input of chemical haulm killers may be reduced. There was a large difference between years in tuber blight after harvest and storage, which confirms that climatic factors are of major importance for tuber infection. The large difference found between the cultivars in the frequency of tuber blight indicates that tuber resistance should be an important part of integrated late blight disease management.

Sammendrag

Experiments of the effect of haulm killing and different other treatments during end of season on tuber blight of potato were presented

Sammendrag

The effect of different end of season treatements of the haulm on tuber blight has beeen investigated in a five year project. Haulm killing reduced the amount of inoculum in the haulm and soil and the amount of tuber blight compared to harvest on green haulm treated with fungicide. The infectivity of the soil was reduced to about the half in three weeks and the infectivity persistes longer in dry soil than in wet soil. Most of the inoculum washed down from the haulm remaines in the top soil, at 15 mm precipitation in pot experiments.

Sammendrag

The prediction of infection periods for lettuce downy mildew (Bremia lactucae) is based on the assumption that spores are produced at night and released in the early morning. The divergent light conditions at Nordic latitudes might affect both sporulation and spore release. Therefore, we monitored release of B. lactucae spores in relation to the climatic conditions in lettuce fields to evaluate the performance of existing forecasting models in timing of fungicide applications for management of lettuce downy mildew in Norway.  In 2005, epidemics were created at two field locations that had no previous lettuce production, and a total of 59 days of spore trapping permitted the study of spore release under natural conditions. Sporulation events were compared to predicted spore production events in Modell-Analys (MA). At the two locations, 76 % and 74 % of the spores were trapped between 08.00 and 16.00, respectively. Spore concentration icreased with decreasing relative humidity (RH), ofting coinciding with increasing solar radiation and temperature. Spore production events predicted by MA were correct at 66 % of the days. However, when the criteria for spore production were adjusted, 78 % of the days were correctly predicted.

Sammendrag

Several models for prediction of infection periods for lettuce downy mildew (Bremia lactucae) are based on the assumption that spores are produced at night and released in the early morning. The divergent light conditions at Nordic latitudes might affect both sporulation and spore release. Therefore, during the period 2001 to 2005 a total of 13 field trials were established in late season lettuce fields to evaluate efficacy of fungicide applications made according to the models PlantPlus (PP) and Modell-Analys (MA) in Norway. Disease severity varied from 0 to 89.4 % in unsprayed control plots at harvest. Fungicide treatments had a significant effect compared to untreated control in all but two of the field trials with disease incidence over 1 % at harvest. Fungicide applications at 10-day intervals and according to PP and MA resulted in an average of 3, 2.5 and 3.3 applications, respectively. There were no significant differences in disease severity at harvest between treatments according to 10-day interval, PP and MA for any of the field trials. Epidemics were created at two field locations that had no previous lettuce production, and a total of 59 days of spore trapping permitted the study of spore release under natural conditions. Spore production events predicted by MA were correct at 66 % of the days. However, when adjusting the criteria for spore production, 78 % of the days were correctly predicted.

Sammendrag

Models for prediction of diseases and pests in fruits and vegetables are important tools in the decision of crop management strategies. In the Nordic countries several models are currently available for the farmers and extension services on the Internet. The most widespread pests and diseases which are forecasted and/or monitored include apple scab (Venturia inaquealis) and apple fruit moth (Argyresthia conjugella) in apples, cabbage root fly (Delia brassicae) and turnip root fly (D. floralis) in Brassica vegetables, carrot root fly (Psila rosea) in carrots, and downy mildews in lettuce (Bremia lactucae) and onion (Peronospora destructor).

Sammendrag

Genetic variation and pathogenicity of Phytophthora infestans isolates collected from organic potato crops of the susceptible cv. Bintje and the moderately resistant cv. Santé were assesed in France, Norway, and the United Kingdom in 2001 and in Switzerland in 2001 and 2002. Population structures differed considerably between the four P. infestans populations. Those from France, Switzerland and the UK were mainly clonal populations showing restricted levels of genetic diversity, whilst those from Norway were mixed A1 and A2 mating type populations with high levels of genetic diversity, suggesting periodical sexual reproduction. Isolates collected from cv. Bintje were on average more aggressive than or comparable to isolates from cv. Santé. Race complexity varied considerably between the regional P. infestans populations with isolates from France and Switzerland showing the highest number of virulence factors. In all pathogen samples but the French, isolates collected from cv. Santé were more complex than isolates collected from cv. Bintje. No directional selection towards increased aggressiveness towards the more resistant cultivar Santé was observed. This suggests that there is no shift towards increased level of pathogenicity in P. infestans populations following the large-scale introduction of more resistant potato varieties in organic production systems in Europe.

Sammendrag

Studies of genetic variation of the late blight pathogen among isolates collected in 2003  in the Nordic countries were presented

Sammendrag

Phytophthora infestans was isolated from potato leaves collected from 200 fields located in different parts of Finland, Denmark, Sweden and Norway in 2003. Sampling was carried out relatively late in the epidemic. The SSR analysis was carried out in Norway. Nine SSR markers were tested; Pi4B, Pi4G, PiG11, Pi02, Pi04, Pi16, Pi26, Pi33 and D13. Based on only 7 SSR markers 190 genotypes were found. Six genotypes occurred twice and one genotype occurred six times. The high genetic variation indicates sexual reproduction in the Nordic late blight population

Sammendrag

Resultater fra isolering av gropflekk fra Hedmark fra sesongen 2006 og PCR data fra Carrotech ble presentert

Sammendrag

We evaluated direct and interactive effects of light quality and intensity, temperature and light, diurnal rhythms, and timing of high relative humidity during long day lengths on sporulation of Bremia lactucae, the causal agent of lettuce downy mildew, using inoculated lettuce seedlings and detached cotyledons. Suppression of sporulation by light was strongly dependent upon temperature and there was little suppression at "10°C. The most suppressive waveband was in the range from 400 to 450 nm, although a lesser effect of wavebands from 450 to 500 and 500 to 550 nm could be detected. At 15°C, near the lower threshold for suppression of sporulation by light, a clear diurnal pattern of sporulation was observed independent of light and darkness. This diurnal rhythm potentially could interact with light and temperature to confound the results of controlled environment studies, and may be the controlling factor in timing of sporulation at low temperatures. Forecasting models that currently use sunrise and sunset to delimit periods conducive to sporulation can be adapted to short nights and extended twilight conditions by incorporating the effects reported herein. Additionally, models of sporulation could be adapted to better reflect a decrease or absence of the suppressive effect of light at

Sammendrag

Bioforsk Plantehelse, sammen med norsk gartnernæring, har utviklet en ny metode som kan påvise klumprot. Metoden har verdi både til å kvalitetssikre småplanteproduksjonen og for å angi smittepress i dyrkingsjord.

Sammendrag

Potettørråte vil også i 2007 kreve en aktiv bekjempelse. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikkel fra i fjor.

Sammendrag

Potettørråte ble i 2006 et lang større problem for mange dyrkere på Østlandet enn det en kunne forvente ut fra klima i juli. Feltforsøk i ulike områder av landet viste at både sprøyting etter ulike varsler og ved faste intervall med dynamiske doser er aktuelle strategier

Sammendrag

Potettørråte ble i 2006 et lang større problem for mange dyrkere på Østlandet enn det en kunne forvente ut fra klima i juli. Feltforsøk i ulike områder av landet viste at både sprøyting etter ulike varsler og ved faste intervall med dynamiske doser er aktuelle strategier.

Sammendrag

Carrot roots with cavity spot lesions from 8 different counties in Norway were sampled and Pythium species were isolated on selective medium. Pythium spp. were characterised morphologically and by species-specific PCR. Laboratory experiments with inoculations of carrot roots were performed. A total of 130 isolates out of 230 Pythium-like isolates tested with PCR were identified as pathogenic species of Pythium. These were P. intermedium (29 %), P. sulcatum (23 %), P. sylvaticum (16 %), P. violae (15 %) and a possible new Pythium species designated P. "vipa" (18 %). There were some difference between geographical regions and ages of cavities regarding the frequency of the different species isolated. When rating sunken lesions in the laboratory inoculation experiments, P. "vipa" was the most aggressive and P. violae the least aggressive species. P. intermedium and P. "vipa" caused more discolouration of the infected carrot tissue than the other species. The importance of the different Pythium spp. as agents of cavity spot in Norway is discussed.

Sammendrag

I to års forsøk med beising av settepoteter med ulik smittegrad av svartskurvsoppen har beising bare ført til litt raskere spiring, og ingen sikre effekter på avlingsmengden og tørrstoff. Settepoteter med lavt smittenivå av svartskurv spirte raskest. Mengsen svartskurv-sklerotier på knollene ble redusert ved beising, men frekvensen av knoller med svartskurv-sklerotier ble ikke redusert. Det ble ikke sikre forskjeller i virkningen av beisemidlene eller påføringsmetodene på avling eller kvalitet.

Sammendrag

Influence of weather conditions on sporangia production, release, viability and infection of potato late blight (Phytophthora infestans) was investigated in Denmark, Norway and Finland using Burkard spore traps and exposure of trap plants in field plots. High amounts of sporangia were trapped after night with long periods with high relative humidity. Sporangia produced in one humidity period were mainly released at the first humidity drop in the morning hours, but there were also some "delayed sporangia release". Local new infections occurred mainly during the morning hours when the leaves were still wet. On many days sporangia did not survive until the afternoon and the results indicate that conditions for survival of sporangia and infection are major bottlenecks for the spread and development of the disease

Sammendrag

Virulence characteristics of Bremia lactucae populations from lettuce crops in the southeast and southwest of Norway from 2001 to 2005 were studied in relation to virulence factors (v-factors) and virulence phenotypes (v-phenotypes). The frequencies of 19 v-factors were analysed, and phenotypic diversity was calculated in relation to v-factors and v-phenotypes. A total of 39 different v-phenotypes were identified from the 58 samples analysed. Four of these were identical with the previously denominated races Bl:17, 18, 22 and 24. The most commonly occurring v-factors were v1, v2, v4, v5/8, v6, v7, v10, v11, v12, v13 and v18. V-factor v17 was not present in any of the tested isolates and v36 was found only once. V-factor v38 was first seen in 2004, coinciding with the observations of broken resistance in many cultivars. The population of B. lactucae in Norway was diverse, but not considerably different from other European populations of this pathogen.

Sammendrag

The Concerted Action on potato late blight `Eucablight" (www.eucablight.org) was launched in 2003 to promote collaboration between researchers across Europe and to collate the previously fragmented data on host resistance to late blight and characterization of its causal pathogen, Phytophthora infestans. Central to the project was the development of standardized protocols, databases and data collection tools with which data from across Europe could be centralized. The ultimate aim was to capitalize on the vast resource of data available in order to allow a pan-European analysis to be conducted. The P. infestans database is currently populated with information relating to over 13,800 isolates from 20 European countries. The host resistance database holds primary disease data and derived statistics from more than 50 field trials assessing mainly foliage blight resistance. The use of seven standard cultivars in these trials facilitated the comparison of resistance information across years and regions. The host database is structured, and made accessible, in such a way that DSS builders can access the model parameters they need to construct locally adapted forecasting systems. In this presentation we describe the data collection and data analyzing tools that have been developed in this project and how they are directly applicable to other host-pathogen systems.

Sammendrag

Because light is assumed to suppress sporulation of many downy mildews (DM), it is a common component in forecast models. We evaluated effects of light intensity and quality, temperature, and diurnal periodicity on sporulation of Bremia lactucae, the causal agent of lettuce DM. We found that suppression of sporulation by light was strongly dependent upon temperature; with little suppression by light below 10 ºC. The greatest suppression of sporulation occurred at 400-450 nm, although a lesser effect was detected at 450-550 nm. At 15 ºC, a diurnal pattern of sporulation was observed independent of light and darkness. Current forecast models for lettuce DM use sunrise and sunset to delimit the hours during which leaf wetness and high RH can induce sporulation. Our results indicate that effects of short nights and extended twilight conditions, as in Nordic countries, should be incorporated into forecast models. Also, temperature should modify model predictions of sporulation, as the suppression of sporulation by light may be greatly reduced at temperatures below 15-20 ºC. The diurnal rhythm could interact with light and temperature to confound the results of controlled environment studies, and may be the controlling factor in timing of sporulation at low temperatures.

Sammendrag

Late blight of potatoes, caused by Phytopthora infestans, is particularly difficult to prevent or control in organic agriculture. In this study, the host resistance of selected varieties to foliar and tuber blight and their yield under organic growing conditions were assessed in trials carried out in four countries (Switzerland, France, England and Norway) in 2001 and 2002. The objective was to identify new, more resistant varieties, which might replace some of the more susceptible varieties which are currently grown in organic agriculture. In each country, five test varieties were compared with two reference varieties, identical for all sites, and two local popular varieties. In addtion, the effect of copper fungicides was assessed for all varieties in England. Several new potato varieties (Appell, Derby, Innovator and Naturelle in Switzerland; Derby, Eden, Escort and Naturella in France; Sarpo Axona, Eve Balfour, Lady Balfour, Sarpo Mira and Sarpo Tomina in England; N89-1756 and N92-1538 in Norway) proved far less susceptible to foliar and tuber blight than most of the varieties currently grown. However, market requirements could restrict their introduction into practice. The copper fungicide treatment reduced foliar blight severity in all varieties tested in England and in both years, by 27 % on average, and increased yield by 20 % on average, but did not affect tuber blight. In organic farming, a shift towards the use of blight resistant varieties should be strongly encouraged, although this is unlikely to eliminate the need to use copper fungicides.

Sammendrag

Cavity spot (Pythium spp.), liquorice rot (Mycocentrospora acerina) and crater rot (Fibularhizoctonia carotae) are important carrot diseases. Cavity spot develops during the growing season, while the latter two are post harvest diseases. Five Pythium "species" were identified as agents of cavity spot in Norway; P. intermedium, P. sulcatum, P. sylvaticum, P. violae and P. "vipa" (probably a new species). Based on unique sequence regions in the ITS, PCR primers were designed to identify the five Pythium "species" and the two post harvest pathogens. PCR detection was species-specific with no cross-reaction to other Pythium species or to other fungal isolates from carrots. At different points in the growing season, soil and carrots were sampled from farm fields in Norway. PCR assays allowed detection of pathogens in both soil and carrot tissue. PCR results from samples of soil adhering to roots late in the growing season corresponded well with the incidence of cavity spot and liquorice rot on carrots after 6 months storage. PCR assay data from soil samples taken within 14 days after sowing carrots also predicted cavity spot incidence reasonably well. There was little incidence of crater rot during the experimental period, which did not allow proper evaluation of the test for F. carotae. Commercial testing of carrot soils is now available through the company "Carrotech" and work is in progress to implement quantitative PCR.

Sammendrag

Potetene vil også i 2006 krever riktig tørråtebekjempelse for å unngå redusert avling og kvalitet. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikkel fra i fjor.

Sammendrag

Light is a common component of forecasting models for downy mildews because its presence is assumed to suppress sporulation. Our objectives were to evaluate the effects of light intensity and quality, temperature, and diurnal periodicity on sporulation of Bremia lactucae, the causal agent of lettuce downy mildew. We found that the suppressive effect of light on sporulation was strongly dependent upon temperature; there was little suppression of sporulation by light at " 10 ºC. At temperatures where light suppressed sporulation, light in the range from 450-500 nm had the most suppressive effect, although a lesser effect of the wavebands from 450-500 nm was detected. At 15 ºC, a diurnal pattern of sporulation was observed independent of light and darkness. In current forecasting models, the time of sunrise and sunset are used to delimit the dark period when leaf wetness and high RH can induce sporulation. In Nordic countries the effects of short nights and extended twilight conditions should be incorporated into forecasting models. Also, since sporulation may be greatly reduced by light at temperatures above 15-20 ºC, this should be used to modify model predictions of sporulation during the time of day when sporulation can occur. The diurnal rhythm could interact with light and temperature to confound the results of controlled environment studies, and may be the controlling factor in timing of sporulation at low temperatures.

Sammendrag

Bladskimmel utgjør et av hovedproblemene i produksjonen av flere grønnsakkulturer på friland. Dette prosjektet har hatt fokus på bladskimmel i salat, løk og agurk, forårsaket av henholdsvis Peronospora destructor, Pseudoperonospora cubensis og Bremia lactucae. I tillegg ble det tatt med en generell kartlegging av sjukdommer i frilandsagurk. I salat ble varslingsmodellen Modell-Analys (MA) og en justert versjon av MA testet i feltforsøk i Lier og Ås. I tillegg ble det tatt i bruk sporefeller i salatfelt i Ås og Ullensvang for å få et sammenligningsgrunnlag mellom varslingsperioder og frigitte sporer av B. lactucae. Sporefellene ga verdifull informasjon og bekreftet at varslingsmodellen MA er et godt utgangspunkt for varsling av infeksjonsperioder for B. lactucae i Norge. I vårløk ble varslingsmodellene MA og DOWNCAST testet i et feltforsøk i Vestfold for å vurdere om disse modellene kan brukes under norske forhold. Flere aktuelle fungicider mot P. destructor ble også prøvd i dette feltet. Begge varslingsmodellene ga varsler som var troverdige i forhold til observasjoner i felt. Acrobat hadde best effekt mot løkbladskimmel av de prøvde fungicidene. I frilandsagurk ble det gjennomført et sortsforsøk og et fungicidforsøk hvor effekten på flere sjukdommer ble vurdert. Hovedproblemene i agurk denne sesongen var bladflekker, og symptomer som lignet agurksvartprikkråte. Signum og Amistar hadde best effekt mot bladflekker, mens ingen av de prøvde midlene hadde effekt mot symptomer på agurksvartprikkråte. Dagens hovedsort "Servus" viste seg å være en av de beste sortene med hensyn på bladflekker. Ved innsamling av prøver ble det konstatert at Ulocladium cucurbitae var den vanligste årsaken til bladflekker. Til tross for mange prøver med symptomer på agurksvartprikkråte var ikke mulig å påvise Didymella bryoniae i prøvene, og det er derfor uklart om det var denne soppen som var den virkelige skadegjøreren. Totalt sett var 2005 et år med forholdsvis lite problemer med bladskimmel. Agurksbladskimmel ble ikke observert og salatbladskimmel ble ikke funnet før seint i sesongen i Lier. Løkbladskimmel medførte store problemer i Vestfold i 2005, mens andre områder med løkproduksjon bare hadde sporadiske forekomster av denne skadegjøreren. Rasetesting av salatbladskimmel bekrefter at det er stor variasjon i den norske populasjonen av denne skadegjøreren.

Sammendrag

Artikkelen omfatter beskrivelse av tørråtesitasjonen i 2004, varsling i VIPS i 2005, fungicider godkjent i 2005 og virkningstabell, fungicidresistens og middelvalg

Sammendrag

Tørråte i potet krever i de fleste potetdistrikter mange sprøytinger for å holdes under kontroll. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikkel fra i fjor.

Sammendrag

Kinakålhoder (Brassica rapa L. pekinensis (Lour.) Hanelt) ble smittet med Phytophthora brassicae De Cock and Man in`t Veld og lagret ved 1.5 ºC i følgende konsentrasjoner av CO2/O2: 0.5/20.5 (kontroll), 0.5/1.5 eller 3.0/3.0. I forsøk med sorten `Nerva", som ble lagret i 94-97 dager, ble infeksjoner forårsaket av P. brassicae signifikant høyere (P < 0.05) i kontrollert atmosfære (CA) sammelignet med kontrollen. In vitro vekst av P. brassicae på agar var imidlertid lavere (P < 0.001) i  CA behandlingene enn i kontrollen. Kjølskade (bladribbenekrose), som ble funnet i sorten `Parkin", var mest fremtredende i kinakål i kontrollen. Lagring i 0.5 % CO2/1.5 % O2 førte til signifikant (P < 0.001) reduksjon av denne skaden, og lavest prosentandel bladribbeneksrose ble funnet ved 3.0 % CO2/ 3.0 % O2. Bladribbenekrose ble ikke fuunnet i sorten `Nerva".

Sammendrag

The pan-European Concerted Action on late blight `Eucablight" was set up and launched in 2003, with the aim of providing tools for investigating variation in both the host and the pathogen. Objectives include the construction of a database, (www.Eucablight.org) containing information on past and current potato cultivars and late blight populations available in the participating countries, and the design, testing and recommendation of protocols for testing host resistance and pathogen diversity. The database is structured, and made accessible, in such a way that many different target groups can use the data for their own purpose. Farmers will be able to find out about the characteristics of the pathogen and the best performing cultivars in their region. DSS advisers will be able to access the model parameters they need to build locally adapted forecasting systems and scientists will be able to employ the data to study host and pathogen interactions, and to place this in an historical perspective. Once the database is operational, maintenance and the entry of new data should take minimal effort. Submission of data is open to anybody who wants to contribute and who follows the standard protocols. We intend the database to generate enough interest to be kept up to date by members of the research community who will continue to submit their results. If this can be achieved, the database will be an important instrument for potato breeders, scientists, advisors and policy makers to follow the co-evolution of host and pathogen in Europe and inform the use of appropriate resistance genes and control measures.

Sammendrag

Økende problemer med soppsjukdommen salatbladskimmel i frilandssalat har medført større behov for sprøyting med soppmidler. Salatprodusentene tok derfor initiativ til et brukerstyrt prosjekt med tittel "Bekjempselse av sjukdommer i salat med minst mulig bruk av kjemiske plantevernmidler". Innen salatbladskimmel har det vært testet ulike varslingsmodeller for beregning av infekjsonsrisiko i tillegg til at en har sett på mulige smittekilder for denne sjukdommen. Prosjektet omfattet også en kartlegging av ulike sjukdommer i salat på friland.

Sammendrag

Svartskurv er en vanlig sjukdom i potet og forårsaker flere ulike symtomer. Artikkelen beskriver symtomene med tekst og bilder. Enkelte norske undersøkelser om utbredelse og skade av svartskurv blir også omtalt

Sammendrag

Svartskurv er en vanlig sjukdom i potet. Ulike symptomer på svartskurv i potet blir beskrevet med tekst og bilder. Artikkelen omtaler også noen norske undersøkelser om utbredelse og skade av svartskurv i potet i Norge.

Sammendrag

Studier av tørråtepopulasjonen i Norge fra 2003 bekrefter tidligere års undersøkelser at den er svært variabel både i genotype og fenotype. Andelen av metalaksyl-resistente individer har gått tilbake. Det er påvist en relativt stor andel isolater som tolererer å vokse på 100 ppm propamokarb, men det er ikke konstatert resistensproblemer i felt. Krysningstype A2 er ikike påvist blant 110 isolater fra Nord-Norge i 2004, noe som antyder at kjønna formering av tørråtesoppen er sjelden eller fraværende i denne landsdelen. Problemene med tørråte i Sør-Norge var mindre i 2004 enn i de foregående årene. Feltforsøk med ulike strategier i 2004 viste at en kunne bekjempe tørråte med godt resultat både med dynamiske fungiciddoser ved faste intervall og ved sprøyting etter ulike varslingsmodeller. Det var imidlertid vanskelig å påvise sikre forskjeller mellom de ulike strategiene.

Sammendrag

De første to årene med forsøk tyder på at sviing av riset 1-2 uker før høsting virker positivt på flere kvalitetsegenskaper, og særlig flassing. Dersom tørråte er til stede vil andelen med tørråte i knollene reduseres ved nedsviing i forhold til ved høsting på grønt ris. For flassing er likevel effekten av sviing liten, i forhold til effekten av faktorer som sort, dyrkingssted og dyrkingsteknikk. Umodne poteter som flasser mye kan ikke "reddes" ved å svi ned riset, og det er derfor viktig med andre tiltak som kan føre til at en høster modne poteter. I forsøkene er det funnet at relativt tidlig setting er gunstig for å motvirke flassing. Lysgroing er nyttig for å motvirke at det tapes for mye avling og tørrstoff ved tidligere avslutning av veksten. Trolig gir det også en svak reduksjon i flassingen, men resultatene fra forsøk i Folva tyder så langt på at denne er usikker og nokså liten. Mer modne poteter ved høsting er vist å kunne gi noe mer svartskurv og sølvskurv.

Sammendrag

I 2003 startet et femårig prosjekt som omfatter vekstavslutning i potet. Foreløpige resultater fra forsøkene med vekstavslutning i sorten Folva viser at risdreping 14 dager før høsting reduserer mengden infektive risrester og jord ved høsting og dermed antall knollinfeksjoner sammenlignet med høsting på grønt ris med eller uten behandling med Shirlan (fluazinam) 7 dager før høsting. Likevel reduserte behandlingen med Shirlan (fluazinam) mengden infektive sporer i jord ved høsting sammenlignet med ubehandlet grønt ris. Vekstavslutningsbehandlingene hadde ingen innvirkning på mengden svartskurv og sølvskurv på knollene, men det ble klart mer skade i ledd som var lysgrodd trolig fordi knollene i disse var med fysiologisk modne.

Sammendrag

Tørråte i potet krever i de fleste potetdistrikter mange sprøytinger for å holdes under kontroll. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikkel fra i fjor.

Til dokument

Sammendrag

Tørråte i potet krever i de fleste potetdistrikter mange sprøytinger for å holdes under kontroll. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikler fra i fjor.

Sammendrag

I 2003 startet et femårig prosjekt i Norge som omfatter vekstavslutning i potet. Studier av tørråte, forårsaket av Phytophthora infestans, på riset, jorda og på knollene er en viktig del av dette prosjektet. Foreløpige resultater med sorten Folva viste at risdreping 14 dager før høsting reduserte antall sporer i riset og i jorda, og reduserte nivået av knollinfeksjoner sammenlignet med høsting på grønt ris med eller uten sprøyting med fluazinam (Shirlan) 7 dager før høsting. Sprøytingen med fluazinam reduserte imidlertid antall levende sporer i jorda ved høsting sammenlignet med ubehandlet grønt ris. Data fra forsøkene  i prosjektet vil bli benyttet til å lage retningslinjer for vekstavslutning i potet blant annet ut fra tørråtesitasjonen i åkeren.

Sammendrag

Light inhibits sporulation of Bremia lactucae, and is a component of models for lettuce downy mildew infection periods, but specific intensities and wavelengths involved are poorly understood. We evaluated environmental data and model performance in Norway for two systems, PlantPlus (PP) and Modell-Analys (MA), which are based on a model developed in California. Disease was detected following forecasts issued by both models in 5 of 8 fields. However, forecasted infection periods were not always followed by disease occurrence. Both PP and MA usually called for fewer fungicide applications than a calendar schedule of sprays at 10-day intervals, with no difference in disease suppression among treatments. Date of initial disease varied widely among sites, and may be related, in part, to light intensity and quality at Nordic latitudes, which differ substantially from those of California. Results of subsequent studies on light effects on B. lactucae will be reported.

Sammendrag

Det er utviklet en DNA-metode basert på PCR-teknikk for påvisning av gropflekksopper, klosopp og gulrothvitflekksopp hos gulrot. Metoden er delvis utviklet og testet ut i et nylig avsluttet brukerstyrt prosjekt. For gropflekksopper var det god sammenheng mellom PCR-resultater fra jordprøver tatt ut om våren og det som ble påvist på røtter etter langtidslagring. For den viktigste lagringssjukdommen klosopp var det best sammenheng mellom PCR-analysene av jord som hang på gulrota i veksttida og det som ble påvist av klosoppråte etter langtidslagring. For gulrothvitflekksopp var det dårlig sammenheng mellom PCR-resultater og påvist skade på gulrota etter lagring i de undersøkte prøvene. Metodikken er søkt patentert av selskapet Carrotech AS.

Sammendrag

Det er utviklet praktiske bioteknologiske metoder basert på PCR-teknikk for påvisning av gropflekksopper, klosopp og gulrothvitflekksopp hos gulrot. Metodene er delvis utviklet og testet ut i et nylig avsluttet brukerstyrt prosjekt. For gropflekksopper var det god sammenheng mellom PCR-resultater fra jordprøver tatt ut om våren og det som ble påvist på røtter etter langtidslagring. For den viktigste lagringssjukdommen klosopp var det best sammenheng mellom PCR-analysene av jord som hang på gulrota i veksttida og det som ble påvist av klosoppråte etter langtidslagring. For gulrothvitflekksopp var det dårlig sammenheng mellom PCR-resultater og påvist skade på gulrota etter lagring i de undersøkte prøvene. Metodikken er søkt patentert av selskapet Carrotech AS.

Sammendrag

Foleløpige resultater tyder på at symptomer på "tørrflekksjuke" i Norge normalt ikke skyldes sopp. Disse brune, tørre flekkene på potetbladene er antakelig et symptom på stress. Man kan derfor trolig ikke sprøyte seg fra problemene.

Sammendrag

NorPhyt er et nytt nordisk samarbeidsprosjekt som skal utvikle varslingsmodeller basert på dagens populasjon av tørråtepatogenet. Eucablight er et nettverk av forskere i Europa som arbeider med sortsresistens og patogenkarakterisering. Norske forsøk gjennomført i 2001-2003 viser at både bruk av lave doser av fungicidet Shirlan rutinemessig og bruk av tørråtevarsler kan redusere fungicidforbruket i forhold til bruk av full dose Shirlan etter rutine. Potensialet for sikker bruk av reduserte doser er størst i tørråtesterke sorter. Forsøk i 2003 viser at bruk av timer med høy relativ luftfuktighet som varselkriterium og systemet "Skimmelstyring" er lovende. Oosporer (hvilesporer) til tørråtepatogenet kan overleve minst fire vintrer i norsk jord. Jord med oosporer kan dermed være en potensiell smittekilde for tørråte i lang tid.

Sammendrag

Tørråte i potet krever i de fleste distrikter mange sprøytinger for å holdes under kontroll. I likhet med de siste årene kommer vi med en omtale av varsling og middelvalg i forbindelse med bekjempelsen av denne viktige skadegjøreren. Artikkelen er en oppdatering av tilsvarende artikler fra i fjor.

Sammendrag

Norge deltar i EU prosjektet Blight-MOP (QLK5-CT-2000-01065) som har som mål å takle tørråte i økologisk potetproduksjon bedre enn i dag. Prosjektet studerer tørråteproblemet fra flere hold og i et systemperspektiv. I tillegg til mer generell informasjon om prosjektet meldes det her om resultater fra sortstestingen i 2001 og 2002. Her ble de mest relevante norske potetsortene sammenlignet med to referansesorter Bintje og Sante. Signifikante forskjeller i tørråteangrep og avling ble registrert. Referansesorten Sante viste en bra toleranse mot tørråte i den forstand at avlingen ble høy også etter et betydelig angrep i løpet av sesongen.

Sammendrag

Experiments were conducted to evaluate potato late blight forecasting models in Norway during 1994-1999. Various adjustments of the Førsund rules (FØR) and the NEGFRY model were compared with routine fungicide applications. In the small plot experiments (n=25) only the fungicide fluazinam was used, but in the large plot experiments (n=13) several fungicides were included according to farmers" practise. A total of seven cultivars were included in the experiments, Beate and Saturna being the principal ones. Generally, fungicide treatments applied in accordance with the straightforward FØR provided acceptable control of leaf and tuber blight. Using forecast techniques, the number of treatments was reduced by 25-50 % compared the routine treatments without causing significantly more disease. There were no significant differences in the late blight control and treatment frequency between forcasts based on FØR, using historical weather data, and NEGFRY, using historical weather data and weather prognoses. The implications of the new pathogen population, cultivar resistance and farmers" acceptance of fungicide applications being related to use of forecasts are discussed.

Sammendrag

I perioden 2000-2003 har det vært et brukerstyrt prosjekt som har arbeidet med å utvikle enkle og praktiske bioteknologiske metoder for påvisning av viktige sjukdomsorganismer hos gulrot. Prosjektet har blitt så vellykket at metodene nå er kommersialisert gjennom selskapet Carrotech.

Sammendrag

Forekomsten av Pythium spp. og Phytophthora spp. i norske veksthus med dyrking av grønnsaker i vannkultur, ble undersøkt i perioden 1990-1995. I tomat og salat var Phytophthora cryptogea den vanligst forekommende arten. I agurk, den mest undersøkte kulturen, var Pythium gruppe F og Pythium irregulare de to dominerende arter. Phytophthora ble ikke funnet på agurk. Patogeniteten til de isolatene som forelå fra undersøkelsen, ble testet på frøplanter av agurk. De mest agressive artene var Pythium aphanidermatum, Pythium ultimum, Pythium paroecandrum og Pythium irregulare.

Sammendrag

Phytopththora infestans is an important pathogen on potato and tomato in Vietnam during the winter season. There are no earlier reports on studies of P. infestans populations in this country. During January 2002 leaf samples were collected from potato and tomato in three provinces in north of Vietnam; Lao Cai, Hanoi and Hai Phong. About 120 pure isolates were obtained. Results from testing of these isolates for mating type, metalaxyl resistance and mitochondrial DNA haplotype will be presented.

Sammendrag

Salatbladskimmel (Bremia lactucae) har forårsaket store problemer i frilandssalat på Østlandet de siste årene. I et forprosjekt i 2001 ble det sett på smittekilder, raser og strategier for bekjempelse med minst mulig bruk av plantevernmidler. Mulige smittekilder er omtalt. Videre er det gitt resultater fra rasetestingen i 2001, og fra feltforsøk med to varslingsmodeller  og ulike fungicider.

Sammendrag

Leaves infected by Phytophthora infestans were collected from potato fields in southern Norway in the growing season of 2000 and 2001. Oospores were found in 8 out of 9 fields, in different cultivars and in unsprayed and sprayed fields. Oospores containing leafdiscs were buried in soil under field conditions in 1998 and tested for viability. There was no decline in viability between burial for 20 and 31 months.

Sammendrag

Artikkelen orienterer om resultater fra det brukerstyrte FoU-prosjektet "Fysiologiske skader og algesoppråte i kinakål".  Algesopp-problemet i kinakål på åkeren og på lager i Lier skyldes to ulike algesopp-slekter.  På åkeren er det Phytium som er hovedproblemet, og da særlig P. tracheiphilum.  Under lagring er Phytophthora porri hovedårsak til algesoppråten.  Ut fra forsøkene med metalaksyl og ulike dekkmaterialer ser infeksjoner av P. tracheiphilum ut til å skje relativt raskt etter planting.  Forsøk i veksthus for å påvise  ulik resistens mot P. tracheiphilum gav variable resultater, og det har vært vanskelig å skille sortenes resistens.  Feltforsøk på areal med naturlig smitte ser ut til å være sikrest metode til å påvise sortforskjeller

Sammendrag

Resultatene fra de to første åra i prosjektet "Frøavl av brytsukkerert" (1998-2000) viste at dårlig spireevne på grunn av angrep av sopper som fører til erteflekk og ertefotsjuke (Ascochyta spp.) er det største hinder for å få til frøavl av "Aslaug" brytsukkerert på friland. Av denne grunn prøvde en i 2000 å finne fram til fungicider for å kontrollere Ascochyta i felt. Innledende in-vitro forsøk ved Planteforsk Plantevernet viste at fludoxinil + cyprodinil (Switch) og pyrimetanil (Scala) var de mest effektive fungicidene, men at også iprodion (Rovral 75 WG), prokloraz (Sportak 45 HF) og tebuconazol (Folicur 25 WG) hadde brukbar virkning mot Aschochyta spp.På dette grunnlag ble de tre handelspreparatene Rovral 75 WG, Switch og Sportak 45 HF valgt ut til feltforsøk på Landvik. Feltet ble anlagt 3.mai 2000, og soppsprøytinga ble utført med 10 dagers mellomrom i perioden 22.juni - 18.august, totalt sju ganger. Sammenlikna med usprøyta kontroll førte regelmessig sprøyting med Rovral, Switch og Sportak til en ikke-signifikant auke i frøavlinga av erter på henholdsvis 18, 14 og 8%. Til tross for en relativt kjølig og fuktig vekstsesong var det lite synlig angrep av Ascochyta i feltet, og spireevnen til ertene var like høy på usprøyta kontrollruter (89%) som på ruter med soppsprøyting (84-90%). En sjukdomsanalyse (felles for alle sprøyteledd) viste at smitte av Ascochyta var til stede på 21% av frøa, men soppen altså ikke fått utvikle seg i skadelig omfang. Parallelt med feltforsøket på friland ble det også gjennomført prebasisavl av erter i plasthus på Landvik. På et effektivt areal på 65 m2 (54 m enkeltrad) ble det her oppnådd ei frøavling på 12 kg, og spireevnen var 97%. Etter tre års arbeid med prosjektet "Frøavl av brytsukkerert" må vi dessverre konstatere at lønnsomheten er for dårlig, og risikoen for stor, til at frøavl av "Aslaug" kan anbefales på friland i Aust-Agder. Forsøka har vist at spireevnen kan bedres ved å velge riktig høsteteknikk, og særlig ved å kutte erteplantene ved rota allerede ved 60-70% vanninnhold i frøa. Nedbørsforholda i august synes likevel å være for ustabile til at frilandsproduksjon kan anbefales. Det meste realistiske alternativet synes nå å at prebasisfrøavlen fortsetter i plasthus på Landvik, mens frøavlen av sertifisert frø (bruksfrø) flyttes til varmere himmelstrøk med mindre nedbør i vekstssesongen

Sammendrag

Potato leaf samples infected by Phytophthora infestans were collected from several potato fields at Jæren, Rogaland county in Norway, at different periods of the growing seasons in 1998 and 1999. Two conventional field and one organic field were sampled at intervals of one to two weeks throughout each season ("test fields"). Isolates of P. infestans were assessed for mating type and metalaxyl sensitivity. In 1998 and 1999,  21.7 % (n=50) and 52.7 % (n=170) of the isolates respectively, were A2 mating type. In most fields, both mating type A1 and A2 were present. A relatively stable frequency of mating type A1 and A2 was found during the season. Among 72 isolates from 1998, 29.2 % of the isolates were metalaxyl-resistant. In 1999,  19.2 % of 83 isolates were metalaxyl-resistant. No significant differences in metalaxyl sensitivity between different sampling dates were found in the test fields. Bulked data from all early and late samples showed a significantly higher percentage of metalaxyl-resistant isolates late in the growing season. A lower frequency of  resistant isolates was found in samples from early potato cultivars than in early samples from late potato cultivars. The implications of the mixed mating type situation and reduced sensitivity to metalaxyl are discussed.

Sammendrag

Tørråte har vært fraværende på Island i mange år, men var vanlig forekommende i 1990 og 1991. Sjukdommen ble ikke observert i 1992-1998. I 1999 ble det igjen funnet tørråteangrep. Blader med tørråte ble sendt til Planteforsk Plantevernet som isolerte soppen og gjennomførte tester av krysningstype og metalaksylsensitivitet. En av 15 undersøkte isolater var A2, de resterende var A1. Metalaksylresistens ble også påvist. Undersøkelsen viser at den "nye" tørråtepopulasjonen også er tilstede på Island.

Sammendrag

Tørråtesoppen førte til stort kjemikalieforbruk grunnet mye primærsmitte og gunstige værforhold for soppen i 2000.  "Ny" tørråtesopp kan også være medvirkende til økt bekjempelsesbehov. Omleggingen av tørråtevarslene fra TELEVIS til Internett har gått tilfredsstillende. Generelt har sprøyting etter varsel fungert godt i 2000, selv om det, som i tidligere år, i enkelte felt er en tendens til noe mer angrep på riset enn der det er sprøytet mer rutinemessig. Tørråtesopp-populasjonen i Norge er svært variabel. Begge krysningtyper er vanlig i Sør-Norge, og er påvist i mange felt gjennom hele sesongen. Krysningstype A2 er nå også funnet i Trøndelag. Oosporer dannes i potetriset og kan overleve minst to vintre under våre forhold. Lav sensitivitet overfor propamokarb er påvist hos enkelte isolat av tørråtesopp i Norge og Finland, men svikt i effekt av Tattoo under feltforhold er ikke rapportert. Reglone har effekt mot tørråtesoppen og innblanding av soppmiddel ved risdreping er derfor unødvendig.

Sammendrag

Phytophthora infestans was isolated from potato leaves and tubers collected from different parts of Norway in 1993-98. Isolates were assessed for mating type, DNA fingerprints, resistance to metalaxyl and virulence phenotype. Differences in the A1/A2 ratio were evident among regions and A2 was not found in northern areas. In the southern part of the country the A2 frequency was relatively stable and 26 % of the isolates (n=1144) was mating type A2. Metalaxyl resistance was found in 31-59 % of the isolates in the period 1996-98 (n=988). All known virulence genes were found among isolates tested in 1996 (n=105), and race 1.3.4.7.10.11 was most common (resistance gene R9 was not included in the differential set). Oospores were observed in potato leaves from three locations in the southern part of Norway. RG57 fingerprints were determined for 102 isolates from 1996. A large number of genotypes and high genetic distances between the genotypes were found, which indicates that sexual reproduction is contributing significantly to the genetic variation of P. infestans in Norway. Validation of the warning system TELEVIS was carried out at one location in 1996-99. Treatments according to TELEVIS resulted in fewer sprays than conventional strategy without significant differences in haulm and tuber infections.

Sammendrag

Phytophthora infestans was isolated from potato leaves and tubers collected from different parts of Finland in 1990-96 and Norway in 1993-96. Isolates were assessed for mating type, resistance to metalaxyl and virulence phenotype. In Finland, 15 % of the isolates (200 isolates tested) and in Norway 25 % of the isolates (642 isolates tested) were A2 mating type. Differences in the A1/A2 ratio were evident among regions and A2 was not found in northern areas. In Finland the frequency of metalaxyl-resistant isolates (1834 isolates tested) decreased from 59 % in 1990-95 to 2 % in 1996. In Norway 59 % of the isolates (491 isolates tested) were resistant to metalaxyl in 1996. All known virulence genes were found in both countries (269 Finnish and 105 Norwegian isolates tested) and race 1.3.4.7.10.11 was most common (resistance gene R9 was not included in the differential set). Oospores were observed in potato leaves from three locations in the southern part of Norway. The implications of the `new" populations in the Nordic countries are discussed

Sammendrag

Infection by Mycocentrospora acerina on carrots were examined in the period 1985 to 1995 in monoculture plots at four sites with crop rotation experiments in Norway. At two of the locations, with the most variable climate, the incidence and severity of M. acerina infections on leaves and roots varied most through the different years. At these locations M. acerina attack on the roots was positively correlated with  precipitation in July. At one location the incidence of leaf infection corresponded significantly with the incidence on the roots. At one site the length of the storage period was correlated with the incidence and severity of liquorice rot in storage.

Sammendrag

Velkommen til  Planteforsk litteraturdatabase/ Welcome to  Planteforsk Literature Database Tittel/Title:  Genetic variability of Phytophthora infestans in Norway and Finland as revealed by mating type and fingerprint probe RG57 Publikasjon: Publication: Mycological Research Volum (Nr): Volume (No.): 103(12) Side: Page: 1609-1615 Utgitt: Published: 1999 Forfatter(e): Author(s): Brurberg, M.B., A. Hannukkala & A. Hermansen Enhet: Research station: Planteforsk Plantevernet Nøkkelord: Keywords: Plantevern, Phytophthora infestans, tørråte, krysningstype, DNA fingerprinting Sammendrag: Abstract: Mating type and RG57 fingerprints were determined for 141 isolates of Phytophthora infestans collected from 63 different fields in all important potato growing areas in Norway and Finland. Seventy-six multilocus genotypes were identified, of which 53 were detected only once. Norwegian and Finnish isolates were similar in terms of genotypic diversity and the genetic distances between the genotypes. The large number of genotypes and the high genetic distances between the genotypes indicate that sexual reproduction is contributing significantly to the genetic variation of P. infestans in Norway and Finland. ISBN: - ISSN: - Pris: Price: - Bestilling: Ordering: - Merknad: Notes: vit44 eng61 pl1 pv21

Sammendrag

Rapporten omfatter studier av svartskurvorganismen (Rhizoctonia solani) og dens virkning på planteutvikling og kvalitet hos potet ved ulike jordtemperaturer, dyrkingstiltak og jordsmittenivå. Resultatene er basert på fire feltforsøk i 1995-96 i Tromsø, samt undersøkelser og forsøk i vekstrom. I vekstromforsøk med 3, 6 og 9 °C som settetemperatur var det ingen systematiske forskjeller i avlingsmengde av potet eller skadeomfang av svartskurvsoppen. I feltforsøkene førte beising til noe forsinket spiring mens avlingsstørrelsen ikke ble påvirket. Beisinga reduserte imidlertid angrepet av svartskurv på underjordiske stengeldeler og førte også til en lavere andel knoller med overflatenekroser og misforming ett av de to forsøksårene. Dyp setting og utsatt settetid senket avlingene og tørrstoffprosenten men virket ikke inn på omfanget av svartskurvskadene. I vekstrom ble det lavere avling, tørrstoffprosent i avlingen og knolltall pr. plante ved jordsmitting med svartskurvsoppen. I tillegg økte prosentandelen knoller med sklerotier sterkt mens det ikke oppsto andre skader på knollene. I felt var det ikke avlingsforskjeller mellom smitta og usmitta jord. Ved smitting ble det imidlertid sterkere skader på underjordiske stengeldeler og større andel knoller med overflatenekroser og misforming.