Impact of specific groups of soil microorganisms on behaviour, bioavailability and biodegradation of pesticides

• Research unit: COST
• Project number: C95.0036

Key words (English)

Sterol demethylation inhibiting fungicides; Difenoconazole; AMF; Mycorrhizae; Degradation

Research programs (English)

COST-Action 66 - Pesticides - sols - environnement

Short description (English)

See abstract

Further information (English)

Full name of research-institution/enterprise: Eidg. Forschungsanstalt für Obst-, Wein- und Gartenbau FAW Pflanzenschutz

Partners and International Organizations (English)

A, B, CH, CRO, CZ, D, E, F, FIN, GR, H, I, N, NL, S, SI, UK

Abstract (English)

Biodegradation on xenobiotics within the complex soil ecosystem is mostly the result of protocoop-eration, 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 mycorrhizal flingi (AMF) enhancing general biological activity in the soil and the accelerating degradation of pesticides was studied. Special attention was given to the ergosterol biosynthesis inhibiting flingicides 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 flingicides. In the second part of the project a bioassay using an especially designed cuvette system was further developed to be used to study the influence of selected AMF-strains on the degradation of difenoconazole. It was demonstrated that difenoconazole did not negatively influence the AMF isolates tested. Difenoconazole did not influence the growth and colonizing ability of AMF. In an experiment under controlled conditions the degradation of difenoconazole was studied in the presence and the absence of AMF. Under the experimental conditions chosen and in the absence of AMF, a fast degradation of difenoconazole was observed at the application rate of 0.13mg a.i./kg soil DT-50 was less than 75 days in three independent experiments. Difenoconazole treated soil was incubated for various time intervals before incubation with AMF for 75 days. When the difenoconazole treated soil was incubated for 75 days then inoculated with AMF and incubated for another 75 days the amount of difenoconazole recovered was slightly below the detection limit after a total incubation period of 150 days. However extrapolated data showed a minute, but statistically significant, difference in the degradation of difenoconazole between the soil with and without AMF. Since the database is rather critical further experiments are needed to confirm this result. When difenoconazole treated soil was inoculated with AMF immediately after the flingicide treatment degradation in soil incubated with AMF was not significantly different from the soil without AMF although a slight tendency to faster degradation in AMF containing soil seems to be detectable. Further experiments are needed to confirm these findings.

References in databases (English)

Swiss Database: COST-DB of the State Secretariat for Education and Research Hallwylstrasse 4 CH-3003 Berne, Switzerland Tel. [phone] Swiss Project-Number: C95.0036