engleski

Imidacloprid degradation in Istrian and Kvarner olive orchard soils

Neonicotinoids are increasingly replacing the organophosphate and methylcarbamate acetylcholinesterase inhibitors which are losing their effectiveness because of selection for resistant pest populations. Imidacloprid is the most important neonicotinoid with low soil persistence, high insecticidal potency and relatively low mammalian toxicity. In Croatia, imidacloprid is most commonly used in olive growing areas, including Istria and Kvarner islands, as an effective mean of olive fruit fly infestation control. This paper describes degradation processes of imidacloprid and investigates the relationships between soil properties (particle size, organic matter content, acidity) and degradation characteristics in four soils, representative of northern Adriatic region, namely island Krk and a coastal Istrian region. Imidacloprid was tested at two doses: 0.5 and 5 mg/kg for 180 days. Residues of imidacloprid and concentration of 6-chloronicotinic acid (6-CNA), which is a degradation product of imidacloprid, were anlayzed by high performance liquid chromatography (HPLC). High clay and organic carbon content and low soil acidity in Istrian soils accelerate degradation rate of imidacloprid, which is adequately described by a first-order kinetic model. The imidacloprid degradation processes are continuous, though not very rapid, with the organic carbon content, as a dominant factor governing degradation. According to half- life of more than 110 days, imidacloprid can be categorized as persistant pesticide. 6-CNA was detected in all soil samples 30 days after apllication. However, liberate usage of imidacloprid can disturb environmental cycling, adversely affecting non-target organisms, including plant and animal species, and thus imposing a risk to the human health.

degradation; imidacloprid; 6-chloronicotinic acid; soil

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