5,870 research outputs found

    Nectria galligena as the cause of a collar rot disease in organically grown Topaz apple trees

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    Symptoms resembling collar rot were detected in organically managed Topaz trees aged 3-10 years, occur-ring one to several years after planting of the orchard. Trees were killed within the same growing season in which symptoms were first observed. The disease commonly progressed as a complete covered canker at the base of the tree trunk. Isolation attempts were negative for Phytophthora and other Oomycetes, but con-sistently yielded Nectria galligena. The possibility of latent (endophytic) infections of N. galligena as the cause of delayed collar rot symptoms is briefly discussed

    Diplodia seriata, cause of black fruit rot in organically grown apples in Holland, Belgium and Northern Germany

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    A fruit rot resembling Gloeosporium infections but appearing on fruits prior to harvest was noticed in organic apple orchards in Holland, Belgium and Northern Germany in 2007. Infections were most commonly observed on ‘Elstar’, but other cultivars were also affected. Fruit colonisation progressed in two steps, whereby a latent stage of sunken black lesions in immature fruits gave rise to a rapidly spreading firm brown rot upon fruit ripening. Isolation experiments from both stages consistently yielded a single species of fungus identified as Diplodia seriata, formerly known under the teleomorph name Botryosphaeria obtusa. Lesions of D. seriata were also seen on leaves as necrotic light brown spots surrounded by a purple halo, and occasionally on small twigs as cankers. Fruit mummies on apple twigs were heavily colonised by D. seriata and are thus likely to carry inoculum for fruit infections during late summer or in the following growing season

    Prvo priopćenje o vrsti Puccinia distincta McAlpine, novoj europskoj hrđi na tratinčicama (Bellis perennis L.) iz Hrvatske

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    Severe rust infections on wild and cultivated daisies (Bellis perennis L.) were found in April and May 2000 in an isolated coastal location of Croatia between Lovran and Opatija. The pathogen was identified as Puccinia distincta McAlpine which has been spreading rapidly across Europe for the past four years and may be of Australian origin. In the current paper, we describe the diagnostic features of P. distincta using Croatian material, and suggest spraying with myclobutanil-containing fungicides to protect ornamental daisies in flowerbeds. Without such treatments, it may no longer be possible to grow daisies in areas affected by P. distincta.TeĆĄka infekcija hrđe na divljim i uzgajanim tratinčicama (Bellis perennis L.) otkrivena je u travnju i svibnju 2000. na izoliranom priobalnom području izme|u Lovrana i Opatije. Patogena gljiva bila je determinirana kao Puccinia distincta McAlpine, koja se protekle četiri godine brzo ĆĄiri po Europi, a moĆŸda dolazi iz Australije. U ovom prikazu opisujemo dijagnostičke značajke gljive P. distincta primjenjujući materijal iz Hrvatske i predlaĆŸemo prskanje fungicidima na osnovi miklobutanila kako bismo zaĆĄtitili dekorativne tratinčice u cvjetnim nasadima. Bez takvih tretmana postoji mogućnost da na područjima zaraĆŸenim s P. distincta viĆĄe neće biti moguć njihov uzgoj

    Konzept zur Reduktion der Regenfleckenkrankheit - Ermittlung von Parametern zur Biologie der Erreger unter westeuropĂ€ischen Klimabedingungen als Grundlage fĂŒr die Weiterentwicklung eines Prognosemodells

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    Ziel des dreijĂ€hrigen Projekts war es, SchlĂŒsselparameter der bisher unter europĂ€ischen Bedingungen nur wenig erforschten Regenfleckenkrankheit (RFK) zu erarbeiten. In den Regionen Altes Land und Bodensee dominierte in allen drei Versuchsjahren (2007 – 2009) ein und derselbe RFK-Erreger, Peltaster sp.. Weitere RFK-Erreger sowie der Erreger der Fliegenschmutzkrankheit (FSK), Schizothyrium pomi, kamen nur sporadisch vor und sind wahrscheinlich fĂŒr die BekĂ€mpfung der Symptome derzeit ohne Bedeutung. In beiden Regionen ist die RFK fast ausschließlich auf ökologisch bewirtschaftete Anlagen beschrĂ€nkt. Eine Besiedlung von Obstanlagen durch RFK-Erreger findet zunĂ€chst von außen statt, kann dann aber in den darauf folgenden Jahren durch endogenes Inokulum getragen werden. Fruchtmumien spielen eine Rolle als endogene Infektionsquellen. Umfangreiche Versuche zur PrĂ€zisierung der Infektionsbedingungen haben ergeben, dass eine Besiedlung der jungen FrĂŒchte bereits zum sehr frĂŒhen Zeitpunkt (T-Stadium, BBCH 74) und danach wĂ€hrend des gesamten weiteren Saisonverlaufs erfolgen kann. Die StĂ€rke der SymptomausprĂ€gung zur Ernte ist in erster Linie davon abhĂ€ngig, wie lange die FrĂŒchte den natĂŒrlichen Infektionsbedingungen ausgesetzt waren. Je spĂ€ter in der Saison Infektionen stattfinden, desto weniger Zeit haben die RFK-Pilze fĂŒr die Besiedlung und Ausbreitung auf der Frucht, so dass spĂ€te Infektionen i.d.R. nicht mehr zu starken Befallsgraden fĂŒhren. Zur AusprĂ€gung von RFK-Symptomen ist Blattfeuchte, auch in Form von Taubildung, ausreichend, jedoch wird die Symptomausbildung mit zunehmenden Niederschlagsmengen deutlich beschleunigt. Sind erste RFK-Symptome in einer Anlage sichtbar, verkĂŒrzt sich die zur Inkubation notwendige kumulative BlattnĂ€ssedauer von etwa 250 auf unter 150 Stunden. Die RFK-Erreger scheinen eine mehrwöchige Trockenphase unbeschadet ĂŒberdauern zu können. Apfelsorten zeigen deutliche Unterschiede in der AusprĂ€gung der RFK-Symptome. Die Ursachen hierfĂŒr mĂŒssen in weiteren Untersuchungen geklĂ€rt werden

    Reaction dynamics in Pb+Pb at the CERN/SPS: from partonic degrees of freedom to freeze-out

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    We analyze the reaction dynamics of central Pb+Pb collisions at 160 GeV/nucleon. First we estimate the energy density pile-up at mid-rapidity and calculate its excitation function: The energy density is decomposed into hadronic and partonic contributions. A detailed analysis of the collision dynamics in the framework of a microscopic transport model shows the importance of partonic degrees of freedom and rescattering of leading (di)quarks in the early phase of the reaction for E > 30 GeV/nucleon. The energy density reaches up to 4 GeV/fm^3, 95% of which are contained in partonic degrees of freedom. It is shown that cells of hadronic matter, after the early reaction phase, can be viewed as nearly chemically equilibrated. This matter never exceeds energy densities of 0.4 GeV/fm^3, i.e. a density above which the notion of separated hadrons loses its meaning. The final reaction stage is analyzed in terms of hadron ratios, freeze-out distributions and a source analysis for final state pions.Comment: 10 pages, 7 figures, Proceedings of the Erice School on Nuclear Physics in Erice, Sicily, Italy, September 17 -25 1998; to be published in Progress in Particle and Nuclear Physics Vol. 4

    Phase chaos in the anisotropic complex Ginzburg-Landau Equation

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    Of the various interesting solutions found in the two-dimensional complex Ginzburg-Landau equation for anisotropic systems, the phase-chaotic states show particularly novel features. They exist in a broader parameter range than in the isotropic case, and often even broader than in one dimension. They typically represent the global attractor of the system. There exist two variants of phase chaos: a quasi-one dimensional and a two-dimensional solution. The transition to defect chaos is of intermittent type.Comment: 4 pages RevTeX, 5 figures, little changes in figures and references, typos removed, accepted as Rapid Commun. in Phys. Rev.

    Topological Lensing in Spherical Spaces

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    This article gives the construction and complete classification of all three-dimensional spherical manifolds, and orders them by decreasing volume, in the context of multiconnected universe models with positive spatial curvature. It discusses which spherical topologies are likely to be detectable by crystallographic methods using three-dimensional catalogs of cosmic objects. The expected form of the pair separation histogram is predicted (including the location and height of the spikes) and is compared to computer simulations, showing that this method is stable with respect to observational uncertainties and is well suited for detecting spherical topologies.Comment: 32 pages, 26 figure

    Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV

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    A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7 TeV is presented. The data were collected at the LHC, with the CMS detector, and correspond to an integrated luminosity of 4.6 inverse femtobarns. No significant excess is observed above the background expectation, and upper limits are set on the Higgs boson production cross section. The presence of the standard model Higgs boson with a mass in the 270-440 GeV range is excluded at 95% confidence level.Comment: Submitted to JHE

    Measurement of the t t-bar production cross section in the dilepton channel in pp collisions at sqrt(s) = 7 TeV

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    The t t-bar production cross section (sigma[t t-bar]) is measured in proton-proton collisions at sqrt(s) = 7 TeV in data collected by the CMS experiment, corresponding to an integrated luminosity of 2.3 inverse femtobarns. The measurement is performed in events with two leptons (electrons or muons) in the final state, at least two jets identified as jets originating from b quarks, and the presence of an imbalance in transverse momentum. The measured value of sigma[t t-bar] for a top-quark mass of 172.5 GeV is 161.9 +/- 2.5 (stat.) +5.1/-5.0 (syst.) +/- 3.6(lumi.) pb, consistent with the prediction of the standard model.Comment: Replaced with published version. Included journal reference and DO
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