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.
2003
Forfattere
Grete StokstadSammendrag
Several factors influence the value of a lamb carcass throughout the slaughtering season, and therefore have implications for the optimal slaughtering time of lambs. The expected price of the carcass varies through the season due to: Variations in the weight of the lambs, and the growth through the season. The classification of the carcass, i.e., the price per kg changes as the lambs grow. The prices of the various quality changes throughout the season. The quality of the grazing fields limits the possible weight gain and influences the classification of lams. The grazing resources are in general limited, and will affect the possibility of fattening lambs in the fall. The objective with this study is to come up with a tool to help in determining when to slaughter which lambs in the fall when resources are limited. In order to make good decisions, the first step is to calculate the profitability of various slaughtering decisions. I use known characteristics of the lambs as weight, sex etc. to determine expected value of the carcass if slaughtered at various point in time in the future. In order to determine expected quality for the carcasses I have used a multinomial ordered probit regression model to determine the probability for obtaining a particular classification. A linear programming model is used to choose the best alternatives given limited grassing resources. The model can be used to determine optimal slaughtering decisions given a particular group of lambs and resources. By limiting the possible choices in the model, the model user may also investigate the losses associated with alternative slaughtering schemes. In this paper I describe the forecasting models for determining the value of the carcass, I describe the general linear programming model and show some results from running the model.
Sammendrag
Neozygites floridana is a fungus in the order Entomophthorales that infects and kills the two-spotted spider mite, Tetranychus urticae. N. floridana is the key regulator factor of T. urticae on maize and soybean in the mid-western and south-eastern USA where farmers are encouraged to adapt their fungicide spray programmes to avoid suppressing the fungus (Cross et al. 1999). To our knowledge few systematic studies have been conducted on N. floridana as a mortality factor of T. urticae in strawberry fields. Some preliminary studies have, however, been conducted in Poland which indicate that N. floridana might be important for the regulation of T. urticae in strawberry. A cropping system that enhances the prevalence of N. floridana might therefore be important for the reduction of T. urticae in strawberry. In our studies we therefore aim to clarify the effect of different strawberry growing systems on the infection level of N. floridana. In one study, the occurrence of N. floridana in T. urticae in organic and conventional strawberry fields was studied in the summer 2002 and 2003. Strawberry leaves were collected from two fields, one organic and one conventional, from each of six different locations in Norway (Lier, Follo, Evje, Finnskog, Kise, Toten). Leaf samples were collected at four-weekly intervals. First sampling was conducted in June/July and the second in July/August. Preliminary results show that N. floridana infected and killed T. urticae in all strawberry fields studied. Infections from 0 to 19% were registered, and the highest infection rates were observed late in the season from the second sampling. Our preliminary results do not show any relationship between occurrence of N. floridana and strawberry cropping systems. The fluctuation in the N. floridana infection rate throughout the season might be higher than observed in the first study. A second study on the infection level of N. floridana in a T. urticae population throughout the season 2003 was therefore conducted in a conventional strawberry field in Follo. Our preliminary results show that the highest N. floridana infection level for this field was around 20%.
Sammendrag
Det er ikke registrert sammendrag
Forfattere
Adugna Haile Trond HofsvangSammendrag
Populasjonsdynamikken til Busseola fusca ble studert 1997-1999 i Halhale og Halhal Begos, henholdsvis 1960 og 1850 m over havet i Eritrea. Busseola fusca hadde tre generasjoner pr. år i Halhale og to i Halhal Begos. Nøkkelfaktoren for dødelighet fant sted hos de aller minste larvene. Dødeligheten på grunn av naturlige faktorer reduserte ikke populasjonen under skadeterskelen. Forskjellige strategier for integrert plantevern diskuteres for å redusere skaden av B. fusca i sorghum.
Forfattere
Lita Greve Sverre KobroSammendrag
I alt 912 individer fra 15 arter Lauxaniidae (Diptera) ble identifisert fra lysfellefangster i årene 1994 til 2002. Tre arter, Meiosimyza decempunctata (Fallén, 1820), M. rorida (Fallén, 1820) and Tricholauxania praeusta (Fallén, 1820) var tilstede i større antall, med varierende forekomst mellom og innen år. Mere enn en tredjedel av artene som er kjent for Norge ble registrert fra én lokalitet
Forfattere
Ali Temiz Morten Eikenes U.C. Yildiz Fred G. Evans Bjørn JacobsenSammendrag
Det er ikke registrert sammendrag
Forfattere
Halvor B. Gjærum Mary Namaganda Kåre A. LyeSammendrag
Sekstini rustarter er beskrevet fra Uganda, 13 av dem nye for Ugandas rustflora, dessuten en del nye vertplanter
Forfattere
Halvor B. Gjærum Mary Namaganda Kåre LyeSammendrag
Det er ikke registrert sammendrag
Forfattere
Tor Håkon SivertsenSammendrag
The main elements of a web-based system for administrating data from a network of automated agro meteorological stations are presented. The concept of quality of meteorological data is then discussed. `Controlling the measurements" is one element contained in the concept of `quality of data". An automatic system for controlling the meteorological data is introduced as mainly a control of the functioning of the instruments. Each instrument is explicitly and uniquely defined in this system, and the different meteorological parameters are uniquely coupled to these instruments. The procedures for automatic control is dependent on the information mentioned above, as well as information dependent on the climate on each site, giving us the expected variation of each parameter through the year. The system also allows automated correction of measured parameter values dependent on the type of instrument used in each case.
Sammendrag
Det er ikke registrert sammendrag