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.
2022
Abstract
Bacterial diseases in woody plants are best characterized for ornamental and fruit trees and much less is known for forest trees. There are many diseases of forest trees whose etiology remains to be clarified and likely more bacterial diseases of forest trees will be discovered in the next years. An overview of the main bacterial pathogens that cause diseases in forest and ornamental trees is described in this chapter and the general differences between fungal and bacterial diseases are outlined. For bacteria pathogenic to trees, six types of diseases are described: Bacterial blight diseases, represented by Erwinia amylovora, the fireblight disease; Bacterial wilt disease, represented by Ralstonia solanacearum species complex; Root and stem galls of trees, represented by Agrobacterium tumefaciens; Wetwood disease, caused by several bacterial genera like Clostridium, Bacillus, Enterobacter, Klebsiella, and Pseudomonas, Xanthomonas and Pantoea; Bacterial scorch disease represented by Xylella fastidiosa with all its subspecies; Bacterial canker represented by Pseudomonas syringae with all its pathovars. Finally, the current diagnostic methods and specific issues related to bacteria detection, together with the main results of the scientific efforts and challenges in the genetic breeding to increase bacterial resistance of trees, are outlined.
Abstract
Pathogenic wood decay fungi such as species of Heterobasidion are some of the most serious forest pathogens in Europe, causing rot of tree boles and loss of growth, with estimated economic losses of eight hundred million euros per year. In conifers with low resinous heartwood such as species of Picea and Abies, these fungi are commonly confined to heartwood and thus external infection signs on the bark or foliage of trees are normally absent. Consequently, determining the extent of disease presence in a forest stand with field surveys is not practical for guiding forest management decisions such as optimal rotation time. Remote sensing technologies such as airborne laser scanning and aerial imagery are already used to reduce the reliance on fieldwork in forest inventories. This study aimed to use remote sensing to detect rot in spruce (Picea abies L. Karst.) forests in Norway. An airborne hyperspectral imager provided information for classifying the presence or absence of rot in a single-tree-based framework. Ground reference data showing the presence of rot were collected by harvest machine operators during the harvest of forest stands. Random forest and support vector machine algorithms were used to classify the presence and absence of rot. Results indicate a 64% overall classification accuracy for presence-absence classification of rot, although additional work remains to make the classifications usable for practical forest management.
Authors
Jorunn BørveAbstract
No abstract has been registered
Authors
Jorunn BørveAbstract
No abstract has been registered
Abstract
No abstract has been registered
Abstract
Strawberry powdery mildew, caused by Podosphaera aphanis, can be particularly destructive in glasshouse and plastic tunnel production systems, which generally are constructed of materials that block ultraviolet (UV) solar radiation (about 280 to 400 nm). We compared epidemic progress in replicated plots in open fields and under tunnels constructed of polyethylene, which blocks nearly all solar UV-B, and two formulations of ethylene tetrafluoroethylene (ETFE), one of which contained a UV blocker and another that transmitted nearly 90% of solar UV-B. Disease severity under all plastics was higher than in open-field plots, indicating a generally more favorable environment in containment structures. However, the foliar severity of powdery mildew within the tunnels was inversely related to their UV transmissibility. Among the tunnels tested, incidence of fruit infection was highest under polyethylene and lowest under UV-transmitting ETFE. These effects probably transcend crop, and the blocking of solar UV transmission by glass and certain plastics probably contributes to the widely observed favorability of greenhouse and high-tunnel growing systems for powdery mildew.
Abstract
No abstract has been registered
Authors
Anne-Grete Roer Hjelkrem Heidi Udnes Aamot Morten Lillemo Espen Sannes Sørensen Guro Brodal Aina Lundon Russenes Simon G. Edwards Ingerd Skow HofgaardAbstract
Fusarium graminearum is regarded as the main deoxynivalenol (DON) producer in Norwegian oats, and high levels of DON are occasionally recorded in oat grains. Weather conditions in the period around flowering are reported to have a high impact on the development of Fusarium head blight (FHB) and DON in cereal grains. Thus, it would be advantageous if the risk of DON contamination of oat grains could be predicted based on weather data. We conducted a functional data analysis of weather-based time series data linked to DON content in order to identify weather patterns associated with increased DON levels. Since flowering date was not recorded in our dataset, a mathematical model was developed to predict phenological growth stages in Norwegian spring oats. Through functional data analysis, weather patterns associated with DON content in the harvested grain were revealed mainly from about three weeks pre-flowering onwards. Oat fields with elevated DON levels generally had warmer weather around sowing, and lower temperatures and higher relative humidity or rain prior to flowering onwards, compared to fields with low DON levels. Our results are in line with results from similar studies presented for FHB epidemics in wheat. Functional data analysis was found to be a useful tool to reveal weather patterns of importance for DON development in oats.
Authors
Katherine Ann Gredvig Nielsen Magne Nordang Skårn Venche Talgø Martin Pettersson Inger Sundheim Fløistad Gunn Strømeng May Bente Brurberg Arne StensvandAbstract
No abstract has been registered
Abstract
In this study, we investigated if a steam treatment program used to produce disease-free strawberry transplants has the potential to also eliminate strawberry mite (Phytonemus pallidus) and two-spotted spider mite (Tetranychus urticae). Crowns of strawberry plants collected in a commercial field, containing young, folded leaves with all life stages of P. pallidus, and strawberry leaf discs on water agar with T. urticae with non-diapausing adult females and eggs from a laboratory rearing, were exposed to warm aerated steam in a steam cabinet in a series of four experimental runs over 2 years. The steam treatments constituted of a 1-h pre-treatment with 37 °C steam followed by a 1-h recovery period at 21–25 °C, and then a main steam treatment at 44 °C for either 2, 4 (both P. pallidus and T. urticae) or 6 h (the more heat tolerant T. urticae only). After steaming, the plant material with P. pallidus or T. urticae were incubated at 21–25 °C until survival was assessed after 1–6 days, depending on the mite species and life-stage. Non-steamed plant material with mites was used as controls. The 4-h treatment killed all P. pallidus eggs, larvae and adults, and the 2-h treatment killed all individuals in all three stages except for one egg in one of the runs. There were no or minor effects of the steam treatments on T. urticae adult and egg survival. Based on these results, the tested steam treatments may be used to eliminate the strawberry mite but not the two-spotted spider mite from strawberry planting material.