Dynamics of residues of mancozeb and its metabolite in litchi and soil.

A field experiment was conducted to reveal dynamics of mancozeb residue and its metabolite ethylenethiourea (ETU) in litchi and soil.Residues of mancozeb and ETU were found mainly in pericarp of litchi,and degraded rapidly.The half-life of the former in litchi was 4.02~5.14 d and of the latter 2.52~3.24 d. And they also degraded rapidly in the soil,with their half-life being 5.63~9.88 d and 4.95~14.2 d,respectively. The results of the two-year experiment show when the litchi were sprayed four times with 1 600 mg·L~(-1) mancozeb 80% WP (1∶500),and the last application was done 10,20 or 30 days before harvesting, the residue of mancozeb in the pulp of harvested fruit was lower than 1 (mg·kg~(-1)),and ETU residue below 0.02 mg·kg~(-1),demonstrating that it is safe to apply mancozeb to litchi with the recommended rate.