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1997

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Sammendrag

This paper analyses a set of policy measures oriented towards reduc ing losses of nitrogen, phosphorus, and soil from agricultural land . An interdisciplinary modelling system- ECECMOD - is presented a nd a set of policy scenarios analysed. The analyses are oriented towards comparing the effects of input-oriented measures (fertilise r taxes) and policy measures directed towards more direct changes in the agronomic practices conducted on the farm. The effects on emission levels, abatement costs, and distributional effect s are documented. The trade-offs between precision and regulation costs are discussed.

1996

Sammendrag

Testicular cancer incidence is increasing rapidly in several countries. Environmental causes acting early in life are suspected but have not yet been identified. We conducted a cohort study to identify parental risk factors for testicular cancer among farmers' sons. Children born in 1952-1991 to parents who were farm holders at the time of the agricultural censuses in 1969-1989 were identified in the Central Population Register (Oslo, Norway). The resulting cohort of male offspring (n = 166,291) were followed up in the Cancer Registry of Norway (Oslo, Norway) for 1965-1991. Exposure indicators were derived from census information on activities on the farm. The cancer incidence was compared with that of the total rural population, and potential risk factors were analyzed by Poisson regression. In a follow-up of 2,924,663 person-years, 158 incident cases of testicular cancer were identified. The study population had a higher incidence of testicular cancer than did the total rural population, particularly at ages 15-19 years and in western Norway. Specific fertilizer regimens on the farm were associated with testicular cancer (rate ratio = 2.44; 95% confidence interval = 1.66-3.56), in particular nonseminoma (rate ratio = 4.21; 95% confidence interval = 2.13-8.32). The rate ratio estimates were highest for boys ages 15-19 years and for a subset of study subjects who were considered more likely to have grown up on a farm. Nondifferential misclassification and bias toward unity are likely because exposure information was available only at the farm level and only for census years. The fertilizer indicators were not available early in life for most subjects, and precise interpretations are difficult. A hypothesis worth considering is that excess nutrient run-off from agriculture constitutes a risk. However, inferences concerning the biological basis of our observations can scarcely be made.

Sammendrag

Studies on the population dynamic of Mamestra brassicae (L.) (Lepidoptera: Noctuidae) were conducted during 1988-1992 in order to improve forecasting and control. The influence of temperature on development, fecundity and survival were investigated in climatic chambers, and lower developmental thresholds and thermal requirements were established for the preoviposition period and the immature stages. Pheromone traps were tested in cabbage fields at 5 locations in south-eastern Norway during 1989-1991. The trap catches were low at all locations and years, and the traps could therefore not be recommended for practical monitoring. A degree-day model for prediction of favourable times for assessment of infestation level and insecticide application was developed, validated and implemented. Mortality in the immature stages, and larval dispersal, was investigated in the laboratory and in the field. Highest mortality was found in first instar larvae and in hibernating pupae. The mortality in first instar larvae was probably caused by failure to locate and establish feeding sites and predation, whereas the winter loss probably was caused by unfavourable weather conditions. Life tables for five generations of a natural population of M. brassicae on white cabbage in Ås during 1988-1992 was constructed and analysed. Generation survival was very low, and the key factor was mortality in small larvae. The stage specific mortality appeared to be mainly density-independent. Parasitoids and pathogens were of little importance in controlling the M. brassicae population, although they were more or less persistently present throughout the experimental period. Trichogramma semblidis (Aurivillius) (Trichogrammatidae) was reared from eggs, and Microplitis mediator (Haliday) and Aleiodes (Aleiodes) sp., both Braconidae, were reared from larvae. Erynia virescens (Entomophtorales) was identified in medium and large larvae. Implications of the results in this study for integrated pest management is discussed, and management tactics are proposed.