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.
1997
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Forfattere
Bjørn ØklandSammendrag
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1996
Sammendrag
The diversity in different groups of obligate saproxylic beetles was related to ecological variables at three levels of spatial scale in mature spruce-dominated forest. The variables were connected to: decaying woodwood-inhabiting fungilevel of disturbancelandscape ecologyvegetational structure. Several strong relationships were found at medium (1 km2) and large scales (4 km2), while only weak relationships were found at a small scale (0.16 ha; 1ha=104m2). This may be explained by the local variations in habitat parameters and the high mobilities of many beetle species. Factors connected to decaying wood and wood-inhabiting fungi were clearly the most important factors at all scale levels. In particular, the variables diversity of dead tree parts, number of dead trees of large diameter and number of polypore fungi species increased the species richness of many groups and increased the abundance of many species. Eight species were not recorded below a certain density of decaying wood per 1 or 4 km2. Former extensive cutting was a negative factor at large scale, probably because of decreasing recolonization with increasing distance to source habitats. Thinning reduced the diversity of species associated with birch. The development of guidelines favouring the diversity of saproxylic beetles are discussed below
Sammendrag
In the present study the predation rate of Chrysoperla carnea (Stephens) on eggs and larvae of the lepidopterous species Mamestra brassicae (L.) was investigated including the prey"s influence on survival and development. The experiments were done at 20 +/- 1 degrees C and L:D = 16:8. C. carnea larvae were fed on eggs and first instar larvae of M. brassicae, respectively. In both cases the daily predation rate of C. carnea increased slowly during the two first instars and reached a peak in the third larval instar. During the third instar 87% and 85% of the total numbers of M. brassicae eggs and larvae, respectively, were consumed. C. carnea preyed on a mean total of 312 M. brassicae eggs and 232 M. brassicae larvae during its larval development. The mean daily predation rate of C. carnea reached a maximum of 106.6 eggs of M. brassicae and 46.1 larvae of M. brassicae. C. carnea consumed a total of 32 mg of M. brassicae eggs and 70 mg of M. brassicae larvae during its larval development. The developmental time of C. carnea fed on M. brassicae eggs and larvae was 27.4 and 21.5 days, respectively. Almost 10% of C. carnea died when reared on M. brassicae eggs and 15% died when reared on M. brassicae larvae. The quality aspect of the prey is discussed.
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Forfattere
Nina JohansenSammendrag
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.
Forfattere
Nina JohansenSammendrag
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