Das Projekt "Auswirkungen bestimmter Gruppen von Bodenmikroorganismen auf das Verhalten, die Bioverfuegbarkeit und den biologischen Abbau von Pestiziden" wird vom Umweltbundesamt gefördert und von Eidgenössische Forschungsanstalt für Obst-, Wein- und Gartenbau, Phytopathologie durchgeführt. Impact of specific groups of soil-microorganisms on behaviour, bioavailability and biodegradation of pesticides. Investigation of the role of the soil microflora concerning behaviour and fate of pesticides. Biodegradation of xenobiotics within the complex soil ecosystem is mostly the result of protocooperation, i.e. the combined, mutually beneficial activities of various types of organisms having different abilities at the same time and site. In particular the role of arbuscular mycorhizal fungi (AMF) enhancing general biological activity in the soil and the accelerating degradation of pesticides is being studied. Special attention is given to the ergosterol biosynthesis inhibiting fungicides which show a relatively high persistency in soil. In the first part of the project a field study showed no accumulation of difenoconazole and penconazole in an orchard that had been treated several years with DMI's. In the second part of the project a bioassay using an especially designed cuvette system is used to study the influence of selected AMF-strains on the degradation of difenoconazole. A preexperiment in which the direct influence of difenoconazole on AMF is tested has been started. Based on previous experience it is assumed that difenoconazole will not influence the growth and colonizing ability of AMF. If so, in a next step the influence of the presence/absence of AMF on the overall degradation of difenoconazole will be tested in the cuvette system.