Chinese cabbage plants were sprayed at weekly intervals until harvest, and residues were monitored at 0, 1, 3, and 7 days after the final spraying. Nu Film 17® did not have any effect in prolonging the residues of cyanofenphos but it prolonged the persistence of malathion. Quinalphos, triazophos, Perthane® (1,1-dichloro-2,2-bis (4-ethylphenyl) ethane), and Tokuthion® (O-ethyl S-n-propyl 0-2,4-dichlorophenyl phosphorodithioate) persisted longer than several others in substantial concentrations. More than 98% of cyanofenphos, 90% of malathion, 75% of malathion metabolite, malaoxon, and ca. 99% of leptophos residues that could be recovered from Chinese cabbage heads were located in the outer 4 leaf layers. Innermost leaves were practically free of insecticide residues. Removal of residues by washing with tap water ranged from 4.5% for fenitrothion to 76% for carbofuran. Substantial portions of triazophos, quinalphos, and Perthane residues also washed off. Boiling reduced residues of malaoxon, quinalphos, fenitrothion, chlorpyrifos-methyl, and Perthane, but the concentrations of residues of cyanofenphos, malathion, leptophos, triazophos, Tokuthion, and carbofuran were increased in boiled cabbage samples. Relatively greater water loss than insecticide loss due to boiling appeared to be the major cause.
Document Type: Research Article
Publication date: December 1, 1977
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