Dissipation and residues of difenoconazole and azoxystrobin in bananas and soil in two agro-climatic zones of China.

Residues of a fungicide suspension (12 % difenoconazole, 18 % azoxystrobin) in bananas and soil were studied under tropical and subtropical monsoon climates, in Hainan and Yunnan provinces, respectively. The half-lives in bananas were shorter in Hainan (difenoconazole: 8.4-10.7 days; azoxystrobin: 7.8-8.4 days) than Yunnan (difenoconazole: 11.3-13.0 days; azoxystrobin: 10.4-11.6 days), possibly because of the higher temperatures and solar radiation levels in Hainan. The half-lives in soil were shorter in Yunnan (difenoconazole: 15.5-16.7; azoxystrobin: 11.9-13.9 days) than Hainan (difenoconazole: 23.1-23.2 days; azoxystrobin: 16.0-16.1 days), possibly because the organic carbon content was higher and rainfall lower in Yunnan than Hainan. Their physico-chemical properties suggest difenoconazole and azoxystrobin should be stable in bananas and soil, but both decreased to safe concentrations by the minimum harvest time after spraying the mixture at the recommended dosage and 1.5 times that dosage, through physical, chemical, and biological processes.