Factors affecting degradation rates of five triazole fungicides in two soil types: 1. Laboratory incubations

✍ Scribed by Bromilow, Richard H; Evans, Avis A; Nicholls, Peter H

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 101 KB
• Volume: 55
• Category: Article
• ISSN: 1526-498X
• DOI: 10.1002/(sici)1096-9063(199912)55:12<1129::aid-ps72>3.0.co;2-u

✦ Synopsis

Triazole fungicides are now widely used commercially and several are known to be persistent in soil. The degradation rates of ®ve such fungicides were measured in laboratory tests with two soils over 720 days, with analysis of soil extracts by high-pressure liquid chromatography. Behaviour in a sandy loam and a clay loam were similar, and incubation of the compounds either singly or in admixture did not in¯uence loss rates except for those of ¯utriafol which were lower in the latter. Triadimefon was quite rapidly reduced to triadimenol, though traces of the former were always found, indicating a possible redox equilibrium. Flutriafol, epoxiconazole and triadimenol (derived from triadimefon) were very persistent, breakdown following ®rst-order kinetics with half-lives greater than two years at 10 °C and 80% ®eld capacity. Propiconazole was moderately persistent, with a half-life of about 200 days under these conditions. Degradation rates increased about 3-fold as the temperature was increased from 5 to 18 °C, though decreasing soil moisture to 60% ®eld capacity only slightly slowed degradation. The rate constants obtained are used in a companion paper describing ®eld studies on these two soils to compare laboratory-measured degradation rates with losses in the ®eld following commercial sprays.