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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.

2011

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Abstract

Experiments were set up over two winter seasons on golf greens i the Nordic countries. Two mowing heights in the autumn and one late application of 0.2 kg N /100 m2 were examined for effects on winter survival and turf performance in the spring. There were small effects from mowing height, but partly significant positive effects of fertilization. The results form annual meadow grass (Poa annua) were not consistent, but red fescue (Festuca rubra), creeping bentgrass (Agrostis stolonifera) and velvet bent grass (A.canina) accorded.

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Abstract

Novel lighting technology offers the possibility of improved arthropod integrated pest management (IPM) in artificially lighted crops. This review compiles the current knowledge on how greenhouse pest and beneficial arthropods are directly affected by light, with the focus on whiteflies. The effect of ultraviolet depletion on orientation and colour-coded phototaxis are to some extent studied and utilised for control of the flying adult stage of some pest species, but far less is known about the visual ecology of commercially used biological control agents and pollinators, and about how light affects arthropod biology in different life stages. Four approaches for utilisation of artificial light in IPM of whiteflies are suggested: (a) use of attractive visual stimuli incorporated into traps for monitoring and direct control, (b) use of visual stimuli that disrupt the host-detection process, (c) radiation with harmful or inhibitory wavelengths to kill or suppress pest populations and (d) use of time cues to manipulate daily rhythms and photoperiodic responses. Knowledge gaps are identified to design a road map for research on IPM in crops lighted with high-pressure sodium lamps, light-emitting diodes (LEDs) and photoselective films. LEDs are concluded to offer possibilities for behavioural manipulation of arthropods, but the extent of such possibilities depends in practice on which wavelength combinations are determined to be optimal for plant production. Furthermore, the direct effects of artificial lighting on IPM must be studied in the context of plant-mediated effects of artificial light on arthropods, as both types of manipulations are possible, particularly with LEDs.

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Abstract

In vitro dose responses of several calcium and potassium salts were determined on some commercially significant plant pathogens including: Helminthosporium solani, Fusarium oxysporum f. sp. pisi race 2, Colletotricum coccodes, Phytophthora cactorum, Phytophthora cinnamomi, Phytophthora erythroseptica, Phytophthora infestans, Phytophthora megasperma, Pythium ultimum and Venturia inaequalis. Mycelial growth inhibition was both salt-specific and dose-related. Pythium ultimum was completely inhibited by ≥75 mg·L-1 calcium propionate, but needed ≥ 300 mg·L-1 of calcium acetate and ≥ 40 mL·L -1 of potassium silicate for complete inhibition. Phytophthora infestans was completely inhibited by ≥150 mg·L-1 calcium acetate, ≥150 mg·L-1 calcium propionate or ≥ 5 mL·L-1 potassium silicate. Phytophthora cactorum was completely inhibited by ≥ 300 mg·L-1 calcium propionate, but required ≥ 600 mg·L-1 calcium acetate and ≥10 mL·L-1 potassium silicate for complete inhibition. Phytophthora cinnamomi was completely inhibited by calcium propionate at ≥ 600 mg·L-1, or by ≥10 mL·L-1 potassium silicate. Only potassium silicate inhibited Phytophthora megasperma, Phytophthora erthroseptica, V. inequalis and H. solani at concentrations of ≥ 5mL·L-1, ≥ 20 mL·L-1, ≥ 40 mL·L-1 or ≥ 80mL·L-1 respectively. Potassium acetate did not completely inhibit any of the pathogens in this study when tested at concentrations ≤ 1200 mg·L-1.

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Abstract

Background: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and resistance to bark beetle colonization. Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle, Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark. Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m22) and 2.6% as much gallery length (0.029 m m22 vs. 1.11 m m22) as trees with low terpene levels (n = 6). There was a highly significant rank correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of ,100 mg terpene g21 dry phloem trees suffered only moderate beetle colonization, and above a high threshold of ,200 mg terpene g21 dry phloem trees were virtually unattacked. Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the impact of tree-killing bark beetles.

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Abstract

Norway spruce (Picea abies) defends itself against herbivores and pathogens by formation of traumatic resin ducts filled with terpenoid-based oleoresin. An important group of enzymes in terpenoid biosynthesis are the short-chain isoprenyl diphosphate synthases which produce geranyl diphosphate (C10), farnesyl diphosphate (C15), and geranylgeranyl diphosphate (C20) as precursors of monoterpenes, sesquiterpenes, and diterpene resin acids, respectively. After treatment with methyl jasmonate (MJ) we investigated the expression of all isoprenyl diphosphate synthase genes characterized to date from Norway spruce and correlated this with formation of traumatic resin ducts and terpene accumulation. Formation of traumatic resin ducts correlated with higher amounts of monoterpenes, sesquiterpenes and diterpene resin acids and an upregulation of isoprenyl diphosphate synthase genes producing geranyl diphosphate or geranylgeranyl diphosphate. Among defense hormones, jasmonate and jasmonate-isoleucine conjugate accumulated to higher levels in trees with extensive traumatic resin duct formation, whereas salicylate did not. Jasmonate and ethylene are likely to both be involved in formation of traumatic resin ducts based on elevated transcripts of genes encoding lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase associated with resin duct formation. Other genes involved in defense signalling in other systems, mitogen-activated protein kinase3 and nonexpressor of pathogenesis-related gene1, were also associated with traumatic resin duct formation. These responses were detected not only at the site of MJ treatment, but also systemically up to 60 cm above the site of treatment on the trunk.