Untersuchungen zur Fangleistung von Schlitzfallen und Fangholzhaufen bei der lokalen Dichteabsenkung von Buchdrucker (Ips typographus)-Populationen

Two kinds of pheromone-based trap systems are used in the integrated system against the European Spruce Bark Beetle: a standardized commercial slot-trap and an attract-and-kill system using insecticide-coated spruce wood. To determine the individual benefits and limits in both systems, a comparative survey has been done in 2008, respecting the slightly different requirements for deploying both systems with maximum efficiency. The observed results showed that both systems are able to attract large numbers of spruce bark beetles, however the wooden attract-and-kill system removed both larger numbers and higher percentages of the attracted individual beetles. During the survey, the wood traps were able to incapacitate between 80 and 90?% of the attracted beetles, while the slot-traps kept only 50?C60?% contained. While the use of a non-specific insecticide in a freely accessible trap system always bears the risk of attracting and killing individuals of non-targeted species, the survey gave no indication that specialised antagonists of the spruce bark beetle or other non-target-species has been overly affected. The percentage of non-target-organisms has been 0.3?% in total. It was concluded that, while both systems have the capability to reduce the local population of European Spruce Bark Beetles, the natural wood trap system using an insecticide has the ability to control a much larger population and should therefore be considered the primary choice if the conditions on the site indicating a high risk of a continuous bark beetle infestation.     

Untersuchungen zur Verticillium-Welke im Hopfenanbaugebiet Hallertau

Verticillium wilt is a devastating disease in hops and causes considerable crop losses. V. albo-atrum is the most widespread species, whereas V. dahliae is rarely found. Due to the survival of the fungus for several years in soil by resting structures and the lack of effective chemical control, a fast detection method is needed. One aim of this study was to evaluate the occurrence of Verticillium spp. in the Hallertau region (Germany). Therefore, 76 hop plants, with or without wilt symptoms, were analyzed using a real time PCR (polymerase chain reaction) assay. V. albo-atrum was identified in 57 bine samples. The pathogen can sporadically appear without showing visual symptoms. The abundance of the fungus inside the plants was analyzed. Furthermore, four beneficial bacteria, Burkholderia terricola ZR2-12, Pseudomonas poae RE*1-1-14, Serratia plymuthica 3Re4-18, and Stenotrophomonas rhizophila DSM14405^T, were evaluated as biological control agents in hops. The colonization competence in the root system, plant growing promotion, and antagonistic effects were assessed. All strains colonized the endorhiza and the rhizosphere. The bacterial strains B. terricola ZR2-12, S. plymuthica 3Re4-18, and S. rhizophila DSM14405^T are promising candidates for further biocontrol strategies. Thus, first steps towards the biological control of Verticillium wilt were presented.     

Untersuchungen zur Keimungsbiologie von sechs tropischen Segetalarten

Investigation of the germination of six tropical arable weeds With the six tropical arable weeds studied, Ageratum conyzoides, Blechum brownei, Crassocephalum crepidioides, Mikania micrantha, Paspalum conjugatum and P. paniculatum, the lowest temperatures at which germination occurred were in the range 10–15(20)°C, the highest up to 40°C, with the optimum between 20°C and 35°C. Ageratum conyzoides and C. crepidioides had lower limits of germination temperature than the other species, which explains their comparatively greater incidence at high altitudes. The germination temperatures of both representative temperate species, Alopecurus myosuroides and Chenopodium album were 5 (minimum), 15–25 (optimum) and 40°C (maximum). The germination of A. conyzoides, C. crepidioides and M. micrantha was reduced by an osmotic potential of - 1 bar. At -4·7 bar only P. paniculatum of the tropical species germinated to a small extent whilst Al. myosuroides and Ch. album were not affected. After storage for a year in dry conditions all six tropical species only germinated when exposed to light. After 20 months, C. crepidioides and P. paniculatum would also do so in the dark.     

Untersuchungen zur biologischen Kontrolle von Schaben mit entomopathogenen Nematoden

Zusammenfassung In Käfigversuchen wurde gezeigt, dass der Nematode Steinernema carpocapsae die Australische Großschabe Periplaneta australasiae infiziert und zum Absterben bringt. Mortalitäten von 50–86% konnten erzielt werden. Dabei wurden verschiedene Köderstationen untersucht. Die höchste Mortalität von 86% wurde in Kleinkäfigen bei Verwendung einer Petrischale als Köderstation erreicht. Die Mortalität in Großkäfigen mit größeren und praxisorientierten Stationen betrug nur 50%. Als Lockmittel für die Köderstation wurden verschiedene Lock- und Futterstoffe geprüft. Die Lockwirkung von Kaffeepulver und Banane war vergleichbar mit der Lockwirkung von handelsüblichen Schabenfallen. Banane wurde zudem bevorzugt als Nahrung aufgenommen. Die Mortalität der Schaben stieg in Abhängigkeit von der Aufenthaltsdauer im Nematodengel von 80% bei 2 min auf 95% nach 30 min. Die Anzahl der Nematoden auf dem Schabenkörper sank dagegen von 431 Nematoden nach 10-minütigem Kontakt mit dem Nematodengel und direkt anschließender Zählung auf 147 Nematoden nach 10-minütigem Kontakt und Zählung nach 24 h. Die Vermutung, dass die Nematoden über die Stigmen eindringen, wird unterstützt durch die vergleichsweise hohe Mortalität von 83% bei Applikation der Nematoden an den Körperseiten von Thorax und Abdomen gegenüber den Mortalitäten bei Auftragung an anderen Körperstellen (65% Behandlung dorsal, Anus 38%, Behandlung ventral 33%, Caput 25%).     

Untersuchungen zur systemischen Infektion von Fusarium culmorum an Winterweizen in Schleswig-Holstein

In north-west Germany Fusarium head blight of wheat (FHB) is frequently caused by Fusarium culmorum and F. graminearum. This damage has, however, mainly been caused by infections during flowering; the incidence of FHB has increased steadily for many years in crop rotations without maize. The authors postulate that F. culmorum can cause systemic infections in wheat. In 2003 they used real-time PCR to analyse more than 1?100 tissue samples from wheat fields in order to determine whether F. culmorum was present in the internodes and spikes of the wheat plants. More than 30% of all analysed samples contained F. culmorum-DNA, and many wheat stems were completely or nearly completely systemically colonized by F. culmorum. These findings are consistent with those of other researchers who have detected a systemic growth of F. culmorum during experiments under controlled conditions. It cannot be automatically assumed that the fungus spreads from the wheat head during flowering; the plant could have become infected through chlamydospores or mycelium on residual plant debris in the soil. Therefore this pathogen must be regarded as a crop rotation disease. F. culmorum is able to severely infect wheat through the roots and stem bases, especially when the soil is dry and warm. Thus, spraying fungicides during flowering is ineffective.     

Untersuchungen zur Europäischen Steinobstvergilbung (ESFY) in Deutschland

From 2003 to 2007 surveys have been conducted in different stone fruit growing regions in southwest Germany to detect European stone fruit yellows (ESFY) disease in Germany. Samplings have been done regularly in selected reference orchards in the regions Neuwieder Becken, Rheinhessen, Vorderpfalz and Südpfalz in summer on trees showing ESFY typical symptoms as well as on branches of trees with unspecific symptoms. All samples have been analysed by PCR for infection with Candidatus Phytoplasma prunorum. The phytoplasma could be detected in all investigated regions on the cultivated Prunus species P. armeniaca, P. persica and P. domestica. No infection was found in wild Prunus species. The main spread of the disease appeared on apricot while peach and European plum were less affected. A good correlation between symptoms and molecular detection of the pathogen could be shown for the typical symptoms in summer and winter for apricot as well as for peach. During regular psyllid captures in the reference orchards the population dynamics of Cacopsylla pruni could be described in southwest Germany for several years. By PCR-testing all collected insects individually a yearly natural infection rate of about 1–2% of all individuals of C. pruni could be calculated.     

Freiland- und Laborversuche zur Validierung von Prognosemodellen des Expertensystems HERBASYS zur Nachbauproblematik nach Herbizideinsatz

Mit den Herbiziden Dicuran (Chlortoluron) und Tramat (Ethofumesat) wurden Freiland- und Laborversuche zur Untersuchung des Abbauverhaltens und der Wirkung auf Nachbaukulturen durchgeführt. Diese dienten der Validierung des Abbausimulations- und des Nachbauprognosemodells des Expertensystems HERBASYS. Die für die Abbausimulation benötigten Modellparameter wurden unter unterschiedlichen Inkubationsbedingungen für verschiedene Böden (toniger Schluff, schluffiger Sand, schluffiger Ton) bzw. mit Hilfe eines iterativen Schätzverfahrens (WALKBACK) ermittelt. Der Abbau beider Wirkstoffe wurde durch die Erhöhung von Bodentemperatur und -feuchte beschleunigt, sofern nicht der Optimalbereich überschritten war. Unter Freilandbedingungen war an den verschiedenen Standorten der Wirkstoffverlust witterungsabhängig, ein deutlicher Zusammenhang mit sorptionsbestimmenden Eigenschaften hingegen war nicht erkennbar. Die simulierten Rückstandsgehalte stimmten insgesamt gut mit den im Freiland gemessenen überein. Eine übertragung der für bestimmte Wirkstoff-Boden-Kombinationen ermittelten Abbauparameter auf andere Standort- und Klimabedingungen war möglich. In Langzeit-Biotesten mit nichtsorptivem Substrat wurden Dosis-Wirkungs-Beziehungen zwischen Chlortoluron und Ethofumesat und verschiedenen Kulturpflanzen ermittelt und in Feldversuchen die Reaktion der Kulturen auf die Herbizide untersucht. Die aus den für den Nachbautermin simulierten Gesamtrückständen und der Sorption berechneten verfügbaren Rückstände wurden für die Nachbauprognose mit den Kenngrößen der Dosis-Wirkungs-Beziehungen verglichen. Das Nachbaurisiko wurde an den verschiedenen Standorten insgesamt gut prognostiziert. Field and laboratory experiments to validate predictory models of the expert system HERBASYS applied to problems of crops following the use of herbicides Field and laboratory studies were conducted with the herbicides Dicuran (chlorotoluron) and Tramat (ethofumesate) to investigate their breakdown behaviour and effects on subsequent crops. These studies served to validate the simulation of breakdown and the predictions for subsequent crops of the expert system HERBASYS. The parameters necessary for the simulation of breakdown were ascertained under different incubation conditions for various soils (clay loam, loamy sand, loamy clay) and with the aid of an iterative method of assessment (WALKBACK). The breakdown of both active substances was accelerated by increases in soil temperature and moisture, insofar as the optimum levels were not exceeded. In the field, breakdown at the various sites was dependent on weather conditions but no clear relationship with sorption-determining properties could be established. The simulated residues accorded well with those measured in the field and it is possible to transfer the breakdown parameters determined for one chemicalsoil combination to other site and climate conditions. In long-term bioassays with nonsorptive substrates dose-effect relationships were established between chlortoluron and ethofumesate and various crop plants and the reaction of the crops to the herbicides was investigated in field tests. The effects of available residues on subsequent crops, as calculated from sowing date and sorption, were compared with those known from the dose-effect relationships. In general, the risk to subsequent crops was well forecasted. Validation par des expériences au champ et au laboratoire des modèles prédictifs du système expert HERBASYS appliqués aux problèmes de cultures succédant à des traitements herbicides Nous avons mené des études au champ et au laboratoire avec les herbicides Dicuran (chlortoluron) et Tramate (éthofumesate) pour étudier leur dégradation et leurs effets sur les cultures suivantes. Le but était de valider les simulations de dégradation et les prédictions valables pour les cultures suivantes dans le cadre du système expert HERBASYS. Les paramètres nécessaires pour simuler la dégradation ont été définis sous différentes conditions d'incubation, pour des sols variés (limon, limon sableux, limon argileux), à l'aide d'une méthode iterative d'évaluation (WALBACK). La dégradation des deux matières actives était accélérée par des accroissements de la température du sol et de son humidité, tant que les niveaux optimums n'étaient pas dépassés. Au champ, la dégradation observée sur différents sites dépendait des conditions météorologiques, mais aucune relation claire avec les propriétés d'adsorption des sols n'a pu être établies. Les teneurs en résidus déterminées par simulation étaient en accord avec celles mesurées au champ et il était possible de transposer les paramètres de dégradation déterminés pour un combinaison matière active-sol à d'autres sites et à d'autres conditions météorologiques. Dans des essais biologiques à long terme sur des substrats non adsorbants, des relations dose-effet ont étéétablies pour le chlortoluron et l'ethofumesate et différentes cultures, et la réponse des cultures aux herbicides a étéétudiée au champ. Les effets des résidus sur les cultures suivantes, dont la teneur était calculée à partir de la date de semis et de l'adsorption, ont été comparées avec ceux déduits des relations dose-effet. En général, le risque pour les cultures suivantes était bien prédit.     

Untersuchungen zur Übertragung von Clavibacter michiganensis ssp. sepedonicus auf gesunde Kartoffelknollen

Zusammenfassung In den Jahren 1999 bis 2003 wurde in Freiland-, Klimakammer- und Lagerungsversuchen überprüft, ob ein Risiko für die Übertragung des Erregers der Bakteriellen Ringfäule der Kartoffel (Clavibacter michiganensis ssp. sepedonicus) besteht, wenn (a) gesunde Kartoffelknollen in Kontakt mit Maschinen und Geräten kommen, die mit dem Erreger kontaminiert sind (indirekter Kontakt) und (b) gesunde Kartoffelknollen direkt in Kontakt mit infizierten Knollen kommen (direkter Kontakt). Nach indirektem Kontakt konnte nur beim nachfolgenden Anbau der kontaminierten Knollen in der Klimakammer Befall in Kraut und Knollen festgestellt werden. Im Freiland konnte der Erreger, auch bei wiederholtem Nachbau der geernteten Knollen, nicht nachgewiesen werden. Nach direktem Kontakt und nachfolgendem Anbau der kontaminierten Knollen in der Klimakammer und im Freiland, wurde der Erreger in allen Fällen in den geerntete Knollen nachgewiesen. Befall im Kraut wurde nur in dem Klimakammerversuch und in einem Freilandversuch ermittelt. Wurden durch direkten Kontakt kontaminierte Knollen eingelagert, konnte der Erreger in allen untersuchten Knollen festgestellt werden. Insgesamt besteht ein hohes Risiko, dass gesunde Knollen infiziert werden, wenn oberflächliche Kontaminationen mit dem Erreger erfolgen. Die Wahrscheinlichkeit von Infektionen steigt mit zunehmender Kontaminationsstärke.     

Untersuchungen zur Vermehrbarkeit der neuen Zierpflanze Clitoria ternatea L. var. pleniflora Fantz

Nowadays, only little information regarding the climber Clitoria ternatea L. var. pleniflora Fantz as “new ornamental plant” does exist in the German-speaking area. This plant is from interest because of its characteristic attractive, bright blue flowers. The vegetative propagation of Clitoria ternatea was investigated at the Institute for Horticultural Sciences, Humboldt-University of Berlin. The objective was to study how different types of cuttings could influence the rooting, proliferation and growth behaviour of greenhouse plants cultivated in two different seasons (summer and autumn). It was found that either stem or tip cuttings from the lower and middle zones of the mother plants with a fully developed leaf are suitable for summer or autumn propagation. Also, it was shown that the cutting variants affected the branching behaviour and further plant growth. Nearly 90% of the trial plants remained with a single shoot. However, in the vegetation period 11% of the plants originating from tip cutting and 14% of the plants originating from stem cuttings could be found with two branches. In autumn, the formation of lateral shoots was strongly declining. Here, the shoot length was particularly influenced by using different types of cutting treatments during propagation. The stem cuttings of the first batch planted clearly developed plants with longer shoots compared to those growing from tip cuttings. In the second batch planted, a lower shoot length growth was generally recorded (means of 5 to 6?cm for the internodes after three-month cultivation). In conclusion, the results regarding the propagation show that C.?ternatea can be recommended as a new ornamental container plant. However, further studies should follow in order to investigate possible photoperiod effects as well as suitable cultivation measures.     

Untersuchungen zum Abbau des Herbizids Chlorphenpropmethyl im Boden und durch Mikroorganismen

Investigations on the breakdown of the herbicide chlorfenpropmethyl in the soil hy microorganisms The herbicide 2-chloro-3-(4-chlorophenyl)propionic acid methyl ester (chlorfenprop-methyl) was hydrolized within a few hours in sandy and loamy soils. The product of the hydrolysis, 2-chloro-3-(4-chlorophenyl)propionic acid (CPP), was metabolized in both soils with a half-life period of 4–8 days when the initial concentration was 22 ppm and of just one day when the initial concentration was 4.4 ppm. In soil 4-chloro-benzoic acid was identified as an intermediary product of the CPP breakdown, and, in mixed cultures of soil micro-organisms, 4-chloro-cinnamic acid as well, In autoclaved soil and soil sterilized with NaN₃ the breakdown of CPP did not take place. The enrichment and isolation of the micro-organisms responsible for the first step in the breakdown of CPP was not possible. Two strains of bacteria isolated from the experimental soils and tentatively attributed to the genera Flavobacterium and Brevibacterium respectively, broke the metabolite 4-chloro-cinnamic acid down to 4- chloro-benzoic acid; two strains of the genus Arthrobacter grew on the 4-chloro-benzoic acid as the only carbon source. The results on the whole support the view that chlorfenpropmethyl is first hydrolized to CPP which is then broken down via 4-chloro-cinnamic acid to 4-chloro-benzoic acid. Further breakdown of 4-chloro-benzoic acid follows by ring cleavage.     

Untersuchungen zur Übertragung von Clavibacter michiganensis ssp. sepedonicus, dem Erreger der Bakteriellen Ringfäule, in das Kraut von Kartoffelpflanzen

From 1999 to 2001, field trials were carried out to find out weather there is a risk of the causal agent of Bacterial Ring Rot of potato (Clavibacter michiganensis ssp. sepedonicus) to be transmitted to the leaves of healthy potato plants via contaminated machinery and equipment during the vegetation period and if so weather the bacteria are transported into the newly formed tubers. Two methods were chosen. Firstly, a sharp-edged metal bar contaminated with a bacterial suspension was drawn through the leaves of potato plants up to 6 times during the vegetation period. Secondly, a suspension of the pathogen was directly injected into the stems of potato plants. The harvested tubers were tested in all trials, leaves were additionally tested in the trial with the contaminated metal bar. The pathogen was not found in any trial. Therefore the risk for the transmission of the Ringrot agent to the leaves of potato plants with contaminated machinery might be very low.     

Weißeln von Obstbäumen zur Vermeidung von Frostrissen und Stamminfektionen mit Pseudomonas syringae

Painting the trunks of deciduous fruit trees white prevents frost injuries. Frost cracks in the bark are important entry sites to the trunk for many plant pathogens such as Pseudomonas syringae, which causes decline of fruit trees. Frost damage and the epiphytic Pseudomonas population on trunks were significantly reduced by painting trees with white paint before the first frost in autumn. A copper compound (Funguran) was added to the paint. This sort of protection from frost injuries relies primarily on the physical effect that the sunlight does not warm the bark, since it is reflected by the white colour. Heating up the bark on the sunny side of the trunk during frost periods leads to tension cracks. A number of products were tested for their stability on bark and their ability to cover trunks and reflect sunlight. Some colours were stable for the whole observation period (more than 100 days) and guaranteed effective heat protection. In conclusion, painting the trunks of deciduous fruit trees white effectively controlled frost cracks. Moreover, the results of a 2-year field trial indicate that trunk infections of Pseudomonas syringae were prevented by using a white paint to which a copper compound was added.     

Einsatz von Bacillus subtilis und Lactobacillus-Stämmen zur Entwicklung technischer Vegetationssysteme für die Gleisbettnaturierung

Zusammenfassung Untersucht wurde, inwiefern sich Lactobacillus ssp. und Bacillus subtilis im Rahmen einer Gleisbettbegrünung positiv auf Wachstumsparameter und Bedeckungsgrad mit Sedum album auswirken. Die Versuche wurden auf den drei Substraten Ziegelbruch, Mineralwollmatten und Geotextilmatten im Jahre 2003 an der Humboldt-Universität zu Berlin durchgeführt. Zusätzlich wurden alle Varianten mit und ohne Nährmedium getestet.Aus den Versuchsergebnissen geht hervor, dass die Substratbeschaffenheiten und die induzierten Bakterienkulturen sehr stark das Pflanzenwachstum beeinflussen. Lediglich Ziegelbruchsubstrat zeigte gute Voraussetzungen für die Entwicklung des aeroben Bakteriums B. subtilis. Dieses ist physikalisch relativ stabil gegenüber Umwelteinflüssen und durch seine grobe Struktur ist auch eine gute Durchlüftung gewährleistet.Die Zugabe eines Nährmediums hatte in allen Versuchen auch ohne Applikation von Bakterien einen entscheidenden Einfluss auf die Wachstumsparameter als auch auf einen frühzeitig hohen Bedeckungsgrad. Drei Monate nach dem Versuchsbeginn konnten keine signifikanten Unterschiede zwischen den Behandlungen mehr nachgewiesen werden. Der Bedeckungsgrad lag zu diesem Zeitpunkt bereits bei mindestens 97%. Der Einsatz der beiden Bodenbakterien und/oder des Nährmediums hatten innerhalb der ersten zwei Monate eine gegenüber der Kontrolle schnellere Bedeckung des Substrats, basierend auf einem verstärkten Wachstum, zur Folge.     

Neue Ansätze zur Optimierung der Kraut- und Knollenfäulebekämpfung im ökologischen Kartoffelanbau

Potato late blight is still an unsolved problem in organic farming. Up to now the disease can only be controlled by copper fungicides. Our project is aiming to reduce the application of copper-containing pesticides by introduction of a blight forecasting system based on meteorological parameters. Primary stem infections should be reduced by seed treatment with copper fungicides thus to postpone the beginning of the blight epidemic as well as the start of spraying. To control secondary infections on the foliage, fungicide strategies should be elaborated to achieve best efficacy with reduced amounts of pesticides. Therefore copper amounts and spraying intervals should be adjusted to the infection pressure. Based on the biological and epidemiological conditions for primary and secondary infections with special emphasis on soil moisture, the potato blight forecast system ÖKO-SIMPHYT should be developed.     

Untersuchungen und Erfahrungen zum Auftreten des Echten Mehltaus (Oidium neolycopersici, ehemals O. lycopersicum) an Tomaten

In 1992 for the first time powdery mildew Oidium neolycopersici (former O. lycopersicum) on tomato was detected. At the same time there were reports about the occurrence of the fungus in different tomato growing areas in Bavaria. Meanwhile powdery mildew is an established fungal disease in the cultivation of tomatoes in Bavaria and other federal states of Germany. On studies concerning the biology and the control of this harmful fungus will be reported in this article.