Degradation of imidacloprid in chrysanthemi flos and soil.

Degradation of imidacloprid in chrysanthemi flos and cultivated soil was studied. The half-lives of imidacloprid were 3.55-5.17 days (soil), 2.10-3.98 days (fresh buds and flowers), 22.14 days (dry flowers, 5°C) and 13.08 days (dry flower, 20°C), separately. The temperature can affect imidacloprid degradation in soil and dry chrysanthemum buds and flowers. Imidacloprid residues in chrysanthemum flowers were more stable during store stage than growing one. Few imidacloprid residues would be dissolved into chrysanthemum tea liquor when the residue in dry buds or dry flowers was below 0.8 mg/kg.