Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2007
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
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 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.
Forfattere
Berit Nordskog Bodil Jönsson Richard Meadow Sverre Kobro Håvard Eikemo Klaus Paaske Irmeli Markkula Arne Hermansen Guro BrodalSammendrag
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
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
Forfattere
Trygve S. Aamlid John Ingar Øverland Sigbjørn Leidal Oleif ElenSammendrag
1. Ugrasmidlet Primus (florasulam) er skånsomt mot timotei, men effektivt mot balderbrå. I motsetning til enkelte andre ugrasmidler, spesielt Hussar, har bruk av dette ugrasmidlet liten betydning for valg av vekstreguleringstrategi i timoteifrøenga. Selv om Primus kan virke bra mot balderbrå også ved litt forsinka sprøyting, bør vi av hensyn til vekstreguleringseffekten unngå tankblandinger av Primus med CCC eller Moddus. I stedet bør vi bruke Primus kort tid etter vekststart, og CCC eller Moddus ved begynnende strekningsvekst to til fire uker seinere. 2. I middel for to forsøk i 2006 gav Amistar Duo 8% avlingsøkning ved bruk sammen med CCC, men ingen avlingsøkning ved bruk sammen med Moddus. Det er behov for flere forsøk med soppbekjempelse i timoteifrøeng, spesielt i annet års og eldre frøeng der halmen er kutta og tilbakeført.
Forfattere
Trygve S. Aamlid John Ingar ØverlandSammendrag
I ei frøeng av "Lea" rødkløver med synlig forekomst av både kløversnutebiller og kløvergnager ble det oppnådd 14% avlingsauke etter sprøyting med pyretroidet Fastac 50 på knoppstadiet, kort tid før begynnende blomstring. Det er behov for mer forskning når det gjelder biologi, varsling og bekjemping av ulike skadeinsekter i norske kløverfrøenger.
Forfattere
Marit AlmvikSammendrag
Models to simulate the fate of pesticides in the environment are frequently used for risk assessments within the registration process. Experimental data are essential for model development, for evaluating the accuracy of models in the description of field behaviour and thus for assessing the confidence that should be placed in model predictions. Various experimental techniques used at Bioforsk Plant Health and Plant Protection Division were described and a short discussion of uncertainty of experimental data given.
Sammendrag
Neozygites floridana is a fungus in the order Entomophthorales that infects and kills the two-spotted spider mite, Tetranychus urticae. The fungus is therefore of interest for the biological control of T. urticae. To obtain information that might help in the use of this fungus under practical conditions in strawberries and cucumbers we have tried to answer the following questions in a series of studies*): 1) When, and at what infection levels does N. floridana occurre in T. urticae populations in fieldgrown strawberries? 2) How and where does N. floridana survive harsh climatic conditions (i.e winter) in Norway? 3) How and where does N. floridana infected T. urticae move and sporulate on a plant? 4) How do commonly used pesticides in strawberries affect N. floridana and T. urticae? 5) How can N. floridana be inoculated in augmentative microbial control of T. urticae? Results show that N. floridana infected and killed T. urticae in 12 out of 12 Norwegian strawberry fields studied. Infection levels up to 90% were observed, and the highest levels were observed late in the season. The infection levels throughout a season varied considerably. N. floridana was observed to overwinter as both hyphal bodies in hibernating T. urticae females from October to at least February at temperatures as low as -20o C. Cadavers with resting spores were found from October to the end of January. Cadavers then probably disintegrated, and resting spores were left on leaves, soil, etc. In a bioassay where a Norwegian N. floridana isolate was tested for numbers and distance of spores thrown at three different temperatures (13o, 18o, 23o C), preliminary results show that high numbers of spores (ca 1300-1900 per cadaver) were thrown at all three temperatures. Further, spores were thrown about the same distance (up to about 6 mm) at all three temperatures. The effects of pesticides used in strawberries on the N. floridana infection level were studied to evaluate factors that might be important for conservation biological control. The pesticides tested were three fungicides; Euparen (tolylfluanid), Teldor (fenhexamid), Switch (cyprodinil +fludioxonil) and one acaricide/ insecticide: Mesurol (methiocarb). The experiment indicated that all three fungicides affect N. floridana negatively but that Euparen might be the least harmful. Mesurol did not affect N. floridana. Our attempts to inoculate N. floridana artificially in a strawberry field has not yet been successful, but we now work on promising methods for inoculation of N. floridana in T. urticae populations in greenhouse cucumbers. More detailed results from the studies referred to in this abstract will soon be published elsewhere.
Sammendrag
To obtain information that might help in the use of Neozygites floridana (Zygomycetes: Entomopthorales) in biological control of Tetranychus urticae (Acari: Tetranychidae), in strawberries and cucumbers we have tried to answer the following questions in a series of studies*): 1) When, and at what infection levels does N. floridana occur in T. urticae populations in field grown strawberries? 2) How does N. floridana survive harsh climatic conditions (i.e winter) in Norway? 3) Where do N. floridana infected T. urticae move and sporulate on a plant? 4) How do commonly used pesticides in strawberries affect N. floridana and T. urticae? 5) How can N. floridana be inoculated in augmentative microbial control of T. urticae? Results show that N. floridana infected and killed T. urticae in 12 out of 12 Norwegian strawberry fields studied. Infection levels up to 90% were observed, and the highest levels were observed late in the season. The infection levels throughout a season varied considerably. N. floridana was observed to over-winter as hyphal bodies in hibernating T. urticae females throughout the winter. Cadavers with resting spores were found from October to the end of January. Cadavers then probably disintegrated, and resting spores were left on leaves, soil, etc. In a bioassay where a Norwegian N. floridana isolate was tested for numbers and distance of spores thrown at three different temperatures (13o, 18o, 23o C), results show that the highest numbers of spores (1886 and 1733 per cadaver) were thrown at 13o and 18o compared to 23o C (1302 per cadaver). Spores were thrown at the same distance (up to about 6 mm) at all three temperatures when cadavers were placed with dorsal side facing up. Cadavers placed with dorsal side down (hanging) threw equal numbers of spores up (on the underside of the leaf in nature) and down (on the leaf below). The effects of pesticides used in strawberries on the N. floridana infection level were studied to evaluate factors that might be important for conservation biological control. The pesticides tested were three fungicides; Euparen (tolylfluanid), Teldor (fenhexamid), Switch (cyprodinil +fludioxonil) and one acaricide/ insecticide: Mesurol (methiocarb). The experiment indicated that all three fungicides affect N. floridana negatively but that Euparen might be the least harmful. Mesurol did not affect N. floridana. Our attempt to inoculate N. floridana artificially in a strawberry field has not yet been successful, but we now work on promising methods for inoculation of N. floridana in T. urticae populations in greenhouse cucumbers. More detailed results from the studies referred to in this abstract will soon be published elsewhere.