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
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.
Sammendrag
Nyttesoppen Neozygites floridana er en viktig naturlig fiende til veksthusspinnmidd. Plantevernmidler, spesielt soppmidler kan hemme denne nyttesoppen. Dette bør det tas hensyn til når en sprøyter mot soppsykdommer i jordbær og i andre kulturer der denne spinnmidden err et problematisk skadedyr.
Forfattere
Trygve S. Aamlid Lars Tørres HavstadSammendrag
Tiller demography and contribution to seed yield were studied in first year seed crops of smooth bromegrass (SB, Bromus inermis `Løfar") and meadow fescue (MF, Festuca pratensis `Salten") planted on different dates and with increasing plant densities (A: 15 Jun. / 11 plants m-2, B: 15 or 30 July / 44 plants m-2, C: 15 August or 10 September /178 plants m-2) in field trials at Landvik, SE Norway. While the total tiller population in most crops increased until seed harvest, it decreased during panicle elongation in crops of SB and MF that had reached 2000 and 3500 tillers m-2 in early spring, respectively. Except for the fact that many of the primary tillers of SB died after producing barren stems, tillers formed in August and September had the greatest chance of becoming reproductive and produced the heaviest inflorescences in both species. Most tillers produced in winter or early spring either remained vegetative or died, but spring-emerging tillers contributed up to 30% of the total seed yield in early-established, low-density crops of MF. It is concluded that spring-emerged tillers contribute more to seed yield in MF than in SB and more in seed crops established early at low plant density than in crops established late at higher density.
Forfattere
Svein Ø. Solberg Kari Bysveen Trygve S. AamlidSammendrag
Subterranean clover (Trifolium subterraneum) as a companion crop during establishment of organic timothy (Phleum pratense) seed crops was examined in four field trials studies in SE Norway from 2001 to 2004. Clover and timothy were either mixed before sowing or seeded in every other row with the possibility of removing winter-surviving plants of clover in the spring of ley year 1. Trifolium alexandrinum, T. resupinatum, T. incarnatum, Melilotus officinalis, Lotus corniculatus and Melicago lupulina were also included in the study, in addition to control plots with no legume companion crop. No manure was applied except to the spring wheat cover crop in the year of establishment. The results showed that subterranean clover was the most promising legume, resulting in a 20 % increase in timothy seed yield in the first seed harvest year. The result could partly be explained by less competition from weeds during the establishment of the seed crop. In autumn of the sowing year, after the wheat had been harvested, subterranean clover covered up to 70 % of the soil surface, leaving less space for weeds. During the following winter, subterranean clover died, leaving more space to the first year timothy seed crop. The positive results with subterranean clover as a companion crop were confirmed by on-farm studies at three different sites. A seed mixture of 0.5-0.7 kg ha-1 timothy and 1.0-1.2 kg ha-1 subterranean clover is now recommended when establishing organic timothy seed crops on farms with no or limited access to manure.
Forfattere
Kari Bysveen Trygve S. Aamlid Svein Ø. SolbergSammendrag
During 2002-2005, Norwegian seed yields of meadow fescue (Festuca pratensis Huds.) were 52% lower in organic than in conventional seed production. The difference was most conspicuous in ley year 1, suggesting that seed crop establishment is a limiting factor in organic seed production. Meadow fescue is usually underseeded in a cover crop of spring wheat or spring barley, and many organic growers delay the underseeding until after harrowing for weed control. Our objectives were (1) to determine whether organic seed crops of meadow fescue should be underseeded in the same operation as, or immediately after, the cover crop (implying no harrowing for weed control); or if they should be underseeded in conjunction with, or just after, weed harrowing (on average nine days after the cover crop); and (2) to compare the establishment of meadow fescue seed crops without cover crop or in cover crops of spring barley, spring wheat, peas or green fodder (barley + peas). On average for all cover crops and four trials, first year"s seed yields of meadow fescue were 11 % lower for crops seeded after weed harrowing than for crop seeded immediately after the cover crop. Weed harrowing combined with delayed seeding also resulted in more scentless mayweed (Tripleurospérmum inodórum) and other weeds in ley year 1. Despite less plant-available nitrogen in spring, seed crops underseeded just after the cover crop were more lodged than crops underseeded after weed harrowing. On average for the two seeding dates, the highest seed yield were produced from crops seeded in pure stand and from crops that had been underseeded in green fodder and received an extra 30 kg N ha-1 in manure shortly after green fodder harvest in late July. The results suggest that seed crops of meadow fescue need ample supply of light, water and nutrients in August to produce a good seed yield in ley year 1.