Data from next generation sequencing indicate the complexity of the birch virome in the urban landscape of Berlin. It is well known that plant viruses are widespread and contribute to the decline of birch trees. A mixed infection by Cherry leaf roll virus (CLRV), Apple mosaic virus (ApMV) and two newly discovered viruses from the genus Badna- and Carlavirus were investigated in southern Berlin (Steglitz-Zehlendorf) in 2015 and 2016. To gain a more detailed view on epidemiology of this viral complex in birch, the study was enlarged in 2017 including eight districts all over Berlin. Birch trees with symptoms like defoliation and degeneration were selected for determination of viral pathogens by molecular biological methods. Within the complex occurring symptoms in birch trees, new types of symptoms have been identified. Different combinations of plant viruses in single and mixed infection were detected by Reverse Transcription- Polymerase Chain Reaction (RT-PCR.) CLRV and Badnavirus combinations have shown to be distinct and widely distributed. Heterogeneity is also known from the symptomatology of virus containing birch leaves. As the correlation of symptoms and viral infection is not shown yet for the mixed infections, it is unknown if the complexity of the virome is the cause of the variability of symptoms. Epidemiology and pathogenicity of the newly discovered viruses as well as species specificity, life cycle, mode of transmission, host plant range and phylogeny are totally unknown and have to be investigated within the next years.

The application of bioinformatic tools on NGS data of birch enables to identify new plant viruses continuously in birch samples from different origin. The virome of birch seems to be more complex and heterogenic as compared to other investigated deciduous trees and this is in some way special. The virome includes DNA as well as RNA viruses with their specific characteristics and they consequently influence the host plants diverse. In 2015 and 2016 the incidence of 4 viruses (CLRV, ApMV, Carlavirus and Badnavirus (Rumbou et al. 2017) of the heterogenic virome of birch was investigated in symptomatic leaves in Berlin (Landgraf et al. 2017). Different combinations of viruses in single and mixed infection were detected by RT-PCR. Some viral combinations are more distinct distributed in Berlin birch than others, so that the question of their relevance in birch and the observed “leaf roll disease” poses. The picture of heterogeneity is also known from the leaf symptomatology in virus containing birch leaves. As the correlation of symptoms and viral infection is not shown yet for the mixed infections, it is unknown if the complexity of the virome is causative for the complicated symptomatology. Epidemiology and pathogenicity of the new discovered viruses as well as species specificity, life cycle, mode of transmission, host plant range and phylogeny are totally unknown and have to be investigated within the next years. References: Rumbou A, Candresse T, Marais A, Theil S, Langer J, Jalkanen R, Büttner C 2017: A novel Badnavirus discovered from betula sp. Affected by birch leaf roll disease, PLOS ONE PONED-17-44140 Landgraf M, Langer J, Gröhner J, Zinnert L, Bandte M, von Bargen S, Schreiner M, Jäckel B, Büttner C, 2017: Viruserkrankungen im urbanen Grün – eine Studie an Birken im Berliner Bezirk Steglitz-Zehlendorf Viral diseases in urban areas – a study on birch in Berlin SteglitzZehlendorf Jahrbuch der Baumpflege, 21. Jg., S. 327–332

Urban climate tolerant tree species will continue to be habitat for many organisms. In that context they are important for the biodiversity of urban ecosystems. Trees are used for food supply by phytophagous organisms, while biological regulatory systems avoid that trees are impacted in their vitality and functionality. This interaction is well studied for established tree species. In contrast there is still little known about these systems on climate tolerant tree species in urban environment. Therefore it was started to determine phytophagous organisms and their antagonists on Ginkgo biloba, Gleditsia triacanthos, Liquidambar styraciflua, Quercus cerris, Quercus palustris, Sophora japonica, Ulmus spp. Resista according to different stands. These studies were made repeated twice a year on leaf samples and one time on branch samples in a period of two years. It turned out that the number of phytophagous arthropods exceeded the number of predators on all tree species. Damages of sucking or chewing insects were rarely found. The spectrum of species was similar but there were elementary differences in the ratio of phytophags and antagonists according to tree species. These first studies do not allow any final conclusion on the sustainable effects of biological regulatory systems on urban climate tree species particularly if they are used in high amounts. Further studies with improved methods are needed to explore this scientific issue.

Berlin hat auf den ca. 40 000 ha begrunter Flache viele Eichen. Im Strasenland ist es die dritthaufigste Baumart mit ca. 37 400 Stuck (9 % des Gesamtstrasenbaumbestandes). Mindestens die gleiche Anzahl an Eichen sind in Parks, Schulhofen, Friedhofen, Freizeiteinrichtungen, privaten Grunflachen (z. B. von Wohnungsbaugesellschaften) zu finden, sie werden allerdings zahlenmasig nicht erfasst. In den Berliner Forsten betragt der Anteil durchschnittlich 13,7 % (3 438 ha).

Need for pest monitoring in town verdure of Berlin Continuous monitoring systems in urban areas are important for protecting the very valuable plant resources in the city. They offer the possibility of an early stage, even at low infestation, with mechanical or biological measures to control pests. Different authors report changes in the pest spectrum of cities. Examples from Berlin are shown to exhibit particularly biting insect groups in the field marked deviations from its previous momentum. Examples of interior planting show also rise in the incidence of sucking pests. The reasons for these short-term changes are complex. The monitoring systems for the various pests of horticulture and forestry are not simply transferred to another in urban areas. Berlin is 892 km(2), the area's largest city in Germany, and highly structured, so that the distribution of the specific monitoring systems will be considered over and over again.

Die Weiße Fliege zählt im Gewächshausanbau mit zu den bedeutenden Schädlingen. Ihre Populationskontrolle mit chemischen Pflanzenschutzmitteln führt oftmals zu Resistenzentwicklungen, ein gestärktes Gesundheits- und Umweltbewusstsein der Gesellschaft fordert die Entwicklung und Nutzung alternativer Möglichkeiten zur Bekämpfung. Eine dieser Möglichkeiten ist der Einsatz von natürlichen Gegenspielern. Um diese adäquat einsetzen zu können, sind Studien zur Biologie, Lebensweise und klimatischen Einsatzbedingungen unerlässlich. In Laboruntersuchungen wurde die Fraßleistung des Nützlings M. pygmaeus an verschiedenen Weiße Fliege-Arten unter unterschiedlichen Temperatur- und Lichtbedingungen geprüft. Die Versuche wurden an Eiern und Larvenstadien von T. vaporariorum und B. tabaci bei variierenden Klimavarianten (Temperatur von 11 bis 22 °C sowie einer Belichtung von 9 oder 16 h) ausgeführt. In den Versuchen mit T. vaporariorum zeigte M. pygmaeus unter allen Temperatur- und Lichtbedingungen einen hohen Wirkungsgrad von 68,4 bis 79,7 %. Bei der Dezimierung von B. tabaci war M. pygmaeus nicht so erfolgreich, der Wirkungsgrad ist im Vergleich zu T. vaporariorum wesentlich geringer und hat eine Spanne zwischen 8,5 und 46,1 %. Die Versuche mit T. vaporariorum zeigten durch die hohe Fraßleistung von M. pygmaeus, dass dieser Nützling bei niedrigen (11–13 °C) und mittleren (18–22 °C) Temperaturen sowohl unter Kurz- als auch Langtagbedingungen erfolgreich auch in Ergänzung mit anderen Gegenspielern von Weißen Fliegen wie beispielsweise E. formosa eingesetzt werden kann. Die Population von B. tabaci wird dagegen nur bei höheren Temperaturen reduziert, wobei der Effekt nicht ausreichend ist.

The parasitoid wasp Pnigalio agraules (Wlk.) is a key natural enemy of the horsechestnut leafminer Cameraria ohridella Deschka and Dimić (Lepidoptera: Gracillariidae). As a basis for mark-release-recapture studies, aimed at investigating the dispersal of this parasitoid in the field, adults of P. agraules were marked using a vertebrate-specific immunoglobulin (IgG). The marker was later detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The IgG was either applied externally by spraying or internally by feeding an IgG-enriched diet. Different concentrations of the marker were used and the influence of abiotic (climatic conditions, time elapsed between marking and marker examination) and biotic factors (sex and age of the parasitoids) on the detection of the immunomarker was tested. External marking by spraying led to more homogeneous labelling than feeding the marker. Parasitoids labelled with 0.25 mg rabbit IgG per ten individuals contained enough immunomarker to be easily distinguished from unmarked ones. Neither the climatic conditions nor the sex or age of the insects had an influence on the detection of the marker. The IgG remained well detectable during the entire lifespan of the parasitoids, which was not negatively affected by the marking procedure. Serological marking can be used to investigate the dispersal behaviour of beneficial insects within mark-release-recapture studies.

Among other approaches, biological control measures against Cameraria ohridella (Lep., Gracillariidae) are tested in the project BerlinCam ("Possibilities to control the horse chestnut leafminer in Berlin", financially supported by the Senate Department of Urban Development Berlin and the EU by means of the EFRE funds). During our investigations, we found 21 parasitoid species on C. ohridella hosts. These species are generalists and known for attacking a broad range of leafininers in Europe. By far the most abundant species is Minotetrastichus frontalis, followed by a second eudominant species, Pnigalio agraules. The structure of the complex and also the parasitism rate is not stable, and we found considerable variations between different generations within one year as well as large variation between the years and the type of habitat in Berlin. Our long-term-monitoring at one location in Berlin shows that parasitism rates are generally very low. The mean parasitism rate of C. ohridella measured over five years was 2,4 % +/- 0,88, 3,7 % +/- 2,18 and 5,3 +/- 5.43 in generation 1, 2 and 3, respectively. The parasitism rate is not dependent on the specific ecosystem. In the project we investigated several aspects of the biology of P agraules. Our results show that this native parasitoid meets several of the requirements for successful use as a bioagent in the control of C. ohridella. The parasitoids' fecundity, longevity and the speed of development by far exceed those of the pest, enabling the parasitoid population to grow faster than that of the host. Future studies on the host preference of this parasitoid species including quantitative aspects regarding release rates will investigate the potential benefits and risks of releases of P agraules for the control of C. ohridella.

Poor synchronisation is considered to be one important reason for the ineffective control of the invasive horse chestnut leafminer by native parasitic Hymenoptera. Parasitoids hibernating in dry horse chestnut leaves break diapause early in spring and presumably leave the vicinity, since no hosts are available when they emerge. As a consequence, the percentage parasitism of the first generation of the leafminer in early summer is low. The experiments presented below were designed to test this hypothesis. Horse chestnut saplings were brought on in a greenhouse and infested artificially with C. ohridella prior to parasitoid emergence in the field. These saplings were then exposed to parasitoid attack under natural conditions to eliminate the synchronisation problem. In addition, the parasitoid complexes of other leafmining hosts, which appear early in the season, were analysed. The results confirm that the most important parasitoids of the horse chestnut leafminer are active early in the season, long before the larvae of the first generation of the host are present. Nevertheless, poor synchronisation with the invasive host did not significantly influence the abundance of the most important parasitoid in the complex, Minotetrastichus frontalis, and consequently had no impact on the parasitism of C. ohridella. Nevertheless, a detailed analysis of the parasitoid community shows that certain species are affected by poor synchronisation, while others are probably limited by ecological parameters, such as a specialisation to foraging in particular strata of vegetation. Several leafmining flies were found early in spring infesting other host plants commonly planted in urban green areas, including species with a parasitoid complex similar to that of C ohridella. The role of these alternative hosts in the food web associated with the horse chestnut leafminer should be subject to further study.

Strains from Paecilomyces fumosoroseus, Lecanicillium muscarium, Metarhizium anisopliae and Beauveria bassiana were examined in standardized Biotest to control the horse-chestnut leaf miner (Cameraria ohridella) in her pupal stage in winter. The fungi were pathogenic against the hibernating pupae of Cameraria ohridella at dose of 1.9 x 10(7) conidia/ml. They were aggressive, led to infection, death and mouldiness of naked pupae. Even at low temperature of 5 degrees C and 12 degrees C. L. muscarium strain V24 showed the highest pathogenicity after 4 weeks against this host, close followed by P. fumosoroseus strain P6. M. anisopliae strain 72 and 8. bassiana strain B412 were also pathogen but after a long-time period. Experiments gave information for general susceptibility of naked pupae of C. ohridella under low temperatures against entomopathogenic fungi. In further examinations it has to be tested, whether fungi can infected, when the pupae stay in their natural surroundings, the pupal cell in the leaf.

The naked pupae of chestnut leafminer Cameraria ohridella are susceptible for entomopathogenic fungi Paecilomyces fumosoroseus strain P6; Lecanicillium muscarium strain V24; Metarhizium anisopliae strain M72 and Beauveria bassiana strain B412. Their activity at low temperature is advantageous especially for the use in the winter season. (Richter et al., 2007a). Therefore the possibility of infection should be examined in biotest for pupae in their pupal cells on leaf of chestnut at conditions Like in winter. Efficacy of entomopathogenic fungi is decreased, if pupae are in their pupal cells. But fungi, especially L. muscarium, proved the ability to infect pupae of C. ohridella in their pupal cells. Infected pupae moulded in their pupal cells after application. Infection doesn't come from spores. In semi field trials with L. muscarium 60% of pupae were infected in their pupal cells and died after incubation with mouldiness.

Ausgehend von den umfangreichen Erhebungen zum Auftreten und zur Verteilung von natürlichen Gegenspielern an Straßenbäumen wurden erste Förder- und Einsatzmaßnahmen an Straßenbäumen am Beispiel der Linde (Tilia cordata Mill.Tilia platyphyllos L.) erprobt. Die unterschiedlichen Ansätze zur Verbesserung des Lebensraumes für räuberische Antagonisten der Lindenspinnmilbe Eotetranychus tiliarium Hermann konnten die Populationen des Schädlings und seiner Gegenspieler nachweislich verändern. Während Unterpflanzungen und Umsetzungsmaßnahmen eine Förderung der Gegenspieler in Dichte und Spektrum förderten, führte die Anwendung von Filzstreifen als Überwinterungshilfe zu einem höheren Spinnmilbenbefall. Auch die Versuche zum Einsatz von standortfremden und standorttypischen Prädatoren der Lindenspinnmilbe zeigten unterschiedliche Ergebnisse auf. Der Einsatz der standortfremden Raubmilbe Amblyseius cucumeris Oudermans zeigte keine Wirkung. Mit der Anwendung von standorttypischen Prädatoren, wie z.B. der Raubmilbe Amblyseius andersonii Chant oder des Kugelmarienkäfers Stethorus punctillum Weise, konnten teilweise gute Wirkungsgrade nachgewiesen werden. Für eine praktikable Nutzung ist die Optimierung ihrer Einsatz- und Förderungskonzepte an Straßenbäumen erforderlich und mittels weiterführender Untersuchungen zu erarbeiten.

Mit dem vermehrten Auftreten neuer Spinnmilben-Arten im Gartenbau und in der Innenraumbegrünung ergibt sich die Notwendigkeit der Suche nach weiteren biologischen Bekämpfungsmöglichkeiten. Es wurden einerseits anhand der Literatur die theoretischen Anwendungsmöglichkeiten von St. punctillum diskutiert, andererseits praktische Versuche in unterschiedlichen Einsatzgebieten durchgeführt. Nach bisherigen Kenntnissen sind weiterführende Arbeiten notwendig, um die prädatorische Leistungsfähigkeit von St. punctillum künftig im Pflanzenschutz nutzen zu können. Untersucht wurde insbesondere die Effizienz von St. punctillum zur Bekämpfung der Problemspinnmilbe T. cinnabarinus in Feld- und Anwendungsversuchen. Hierzu können jedoch noch keine endgültigen Aussagen getroffen werden. Man konnte beobachten, dass die Gemeine Spinnmilbe T. urticae als Beute bevorzugt wird. Des weiteren wurde festgestellt, dass im Gewächshaus eine Brechung der Diapause durch 10 h Licht möglich ist.

Zusammenfassung:Eine umfangreiche Analyse über Biologie und Systematik von M. pygmaeus wurde durchgeführt. Es konnte anhand von Literaturnachweisen und eigenen Untersuchungen aufgezeigt werden, dass M. pygmaeus als potentieller, universell einsetzbarer Räuber zur Dezimierung von unterschiedlichen Gewächshausschädlingen geeignet ist. Er bietet aufgrund seiner Ernährungs- und Lebensweise Vorteile gegenüber bisher verwendeten Gegenspielern. Sein Einsatz ist dort empfehlenswert, wo starke Schädlingspopulationen vorhanden sind, wo neue Schädlingsarten biologisch bekämpft werden müssen, wo vorbeugende biologische Methoden effizient sein sollen und dort, wo die Bedingungen für Parasitoide ungünstig erscheinen. Nachteilig ist seine hohe Empfindlichkeit gegenüber systemischen Insektiziden. Hierfür wurden umfangreiche Untersuchungen mit den Wirkstoffen Imidacloprid, Thiacloprid und Azadirachtin durchgeführt und diskutiert.Summary:An extensive analysis biology and systematic of M. pygmaeus was enforced. It could be shown on the basis of literature-proof and examinations, that M. pygmaeus is a potential, universally employable beneficial organism for the decimation of different greenhouse-pests. M. pygmaeus has on the basis of its nutrition and of its way of life advantages compared with beneficial applied until now. Its use is commendable where strong pest-populations exist, where new pest-types must be fought biologically, where preventive biological methods should be efficient and where the conditions appear for parasitoide as unfavorable. Its high sensitivity against systemic insecticides is disadvantageous. Extensive examinations were enforced with the systemic insecticides Imidacloprid, Thiacloprid and Azadirachtin and were discussed.

The parasitism of the horse chestnut leaf miner (Cameraria ohridella) in the city of Berlin is currently being studied within the project BerlinCam. The project involved intensive field studies at 7 horse chestnut stands in different types of habitats, spanning three vegetative periods, to understand the influence of abiotic and environmental factors on parasitoid complexes and para- sitism rates. 16 species of parasitoids have been determined so far, most of them generalistic mem- bers of the chalcidoid family Eulophidae. The parasitism rates as well as the numbers of parasitoid species were, on average, lower in 2004 than in 2003, which may be a result of different weather conditions in these two years. Surprisingly, the highest rates of parasitism were measured along streets in the city centre, whereas they were significantly lower at semi-natural stands outside the city. Several environmental factors, like the presence of other leafminers in the surrounding vegeta- tion or the population density of C. ohridella at the locations may be responsible for these results.

Strategies to control the horse chestnut leafminer (Cameraria ohridella) in urban environments. The continuous epidemic infestation of horse chestnuts by C. ohridella is a serious aesthetic and economic problem in urban environments. The project "BerlinCam", therefore, aims to develop control measures which meet the special needs of urban plant protection. Chemical treatments using a recently developed application method achieved a substantial reduction of the infestation level of horse chestnut leaves by the pest insect. Easily practicable and safe depot-applications of systemic insecticides turned out to be effective in killing preimaginal stages of the leafminer on young trees. Questions regarding potential environmental risks and economic practicability of these methods will be answered in the next two years of the project. So far, chemical products are not registered in Germany.