Publications
NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.
2007
Authors
Roshan M. Bajracharya Bishal K. Sitaula Subodh Sharma Alhaji S. JengAbstract
No abstract has been registered
Abstract
In winter 2000-2001, there was a serious outbreak of Gremmeniella abietina Morelet in southeastern Norway. During the outbreak, we noted that injured Scots pine trees (Pinus sylvestris L.) developed secondary buds in response to the fungus attack, and we decided to study the relationship between injury, appearance of secondary buds and recovery of the trees thereafter. For this purpose, 143 trees from 10 to 50 years of age were chosen and grouped into crown density classes. Injury was assessed in detail, and buds were counted before bud burst in the spring of 2002. In addition, a subset of 15 trees was followed through the summer of 2002 to assess recovery. All injured trees developed secondary buds, with a clear overweight of dormant winter buds in proportion to interfoliar buds. Healthy control trees did not develop secondary buds at all. The secondary buds appeared predominantly on the injured parts of the tree; interfoliar buds in particular developed just beneath the damaged tissue. Most of the secondary buds died during the winter of 2001-2002, mainly because the fungus continued to spread after the first outbreak. Many of the remaining buds developed shoots with abnormal growth during the summer. Secondary buds may help trees to recover from Gremmeniella attacks, but this strategy may fail when the fungus continues to grow and injure the newly formed buds and shoots.
Authors
Michelle de Chantal Kjersti Holt Hanssen Aksel Granhus Urban Bergsten Mikaell Ottosson-Löfvenius Harald GripAbstract
We studied first winter frost-heaving damage to one-year-old Picea abies (L.) Karst. seedlings planted in gaps made by group fellings (large circular gaps, ca. 500 m(2)) and single-tree selection cuttings (small irregularly shaped gaps, ca. 175 m 2), as well as in uncut forest. One-month-old seedlings were planted on manually exposed LF, Ae, and B horizons that emulated various intensities and depths of scarification. The three experimental sites were located in multistoried Pinus sylvestris L. or P. abies forests on sandy loam or silt loam in southeastern Norway. Altogether, 5% of seedlings sustained frost heaving damage on the LF horizon, compared with 20% on the Ae horizon and 45% on the B horizon. On average, 31% of the seedlings in large gaps incurred frost-heaving damage compared with 20% in small gaps and 19% in uncut forest. Exposed roots and poorly anchored or uplifted seedlings were recurring classes of damage, especially on the B horizon and in large gaps. The above- versus below-ground biomass ratio of seedlings was higher on the B than on the Ae horizon in uncut forest and large gaps, inferring broken roots. Therefore, to reduce the risk of frost-heaving damage, shallow soil preparation and smaller gap sizes should be used.
Authors
Eivind Vangdal Finn Måge Aksel DøvingAbstract
No abstract has been registered
Authors
Finn Måge Aksel Døving Eivind VangdalAbstract
No abstract has been registered
Authors
Ragnhild Hafskjold Nærstad Arne Hermansen Tore BjorAbstract
Field trials in 1996, 1997 and 1998 with six potato cultivars differing in levels of foliar and tuber race-nonspecific resistance to late blight were treated with 100, 50 and 33% of the recommended dose of the fungicide fluazinam at application intervals of 7, 14 and 21 days. Using a mixed inoculum of six or seven indigenous isolates of Phytophthora infestans small potato plots were inoculated via infector plants. A foliar blight model for the relationship between the effects of resistance, fungicide application and disease pressure was developed using multiple regression analysis. Cultivars with a high level of quantitative resistance offered the greatest potential for fungicide reduction. The model showed that the effect of resistance on integrated control increased exponentially with increasing cultivar resistance. Reducing fungicide input by lowering the dose resulted in less foliar disease than extending application intervals. The higher the disease pressure, the greater the risk associated with reducing fungicide input by extension of application intervals. The field resistance of cultivars to tuber blight mainly determined the frequency of tuber infection. Exploiting high foliar resistance to reduce fungicide input carried a high risk when cultivar resistance to tuber blight was low. When field resistance to tuber blight was high, a medium level of resistance in the foliage could be exploited to reduce fungicide dose to c. 50%, provided application was at the right time. At a high level of field resistance to both foliar and tuber blight, application intervals could be extended.
Authors
Pål Tore Mørkved Peter Dörsch Anne Kristine Søvik Lars R. BakkenAbstract
No abstract has been registered
Authors
Arnstein Staverløkk May-Guri Sæthre Eline HågvarAbstract
No abstract has been registered
Authors
Yibrah Beyene Trond Hofsvang Ferdu AzerefegneAbstract
The egg parasitoid O. epuhts and the pupal parasitism caused by the P. foveolatus and Mesopolobus spp. were the key mortality factors in the population dynamics of the C. similis. The egg and pupal parasitism were density dependant at two and one locality, respectively. (c) 2007 Elsevier Ltd. All rights reserved.
Authors
Ingunn Molund Vågen Trygve Aamlid Arne Oddvar SkjelvågAbstract
The effects of three nitrogen (N) fertilizer rates (0, 120, and 240 kg N ha(-1)) and two planting times (May or late June/July) on yield and N use of the early cultivar 'Milady' and the late cultivar 'Marathon' of broccoli (Brassica oleracea var. italica) were investigated on three silty loam soils varying in soil mineral N (Nmin) in the southernmost part of Norway during 1999 and 2001. In all crops receiving fertilizer, rapid uptake of N started about three weeks after planting. The relative yield of broccoli heads increased with increasing soil available N (fertilizer N plus Nmin) at planting to 200-250 kg N ha(-1) and then levelled off. The two lower fertilizer rates were more restrictive to yields in early-planted than in late-planted crops. A general increase in harvest index with increasing N rate reflected a stronger effect of N on the head yield than on the total above ground biomass production. The apparent recovery of fertilizer N decreased with increasing N rate and was on average 74% in total above ground biomass and 25% in broccoli heads. Despite a higher N uptake, the average soil mineral N level at harvest increased from 12 kg N ha(-1) on unfertilized plots to 27 and 78 kg N ha(-1) on plots receiving 120 and 240 kg N ha(-1), respectively; this increase was stronger in early than in late plantings and stronger in 'Milady' than in 'Marathon'. The yield of broccoli heads was similar in the two cultivars, but 'Milady' had a lower total biomass production and thus a higher harvest index, presumably due to earlier head initiation.