UPTAKE OF EMAMECTIN BENZOATE RESIDUES FROM SOIL BY ROTATIONAL CROPS

Radiocombustion analyses of barley, carrots, and lettuce planted in 30 , 120, 141, and 365-DAT plots after applications of the test compound [C-14]4 ''-deoxy-4 ''-epi-methylaminoavermectin B1a ([C-14]-MAB1a; 0.1 008 kg ai ha(-1)) demonstrated that total residues in edible lettuce a nd carrots were below the limits of quantitation (LOQ; <4 mu g/kg). Hi ghest residue levels of 16 and 30 mu g/kg were found, respectively, in 30- and 141-DAT plot barley straw. In both straw samples, percentages of extractable and unextractable radioactivity were similar, averagin g 54 and 46%, respectively, of total radioactivity. Cellulase/hemicell ulase digestions of resulting marcs indicate that some radioactivity w as incorporated into plant natural products. Extractable residues in s traw and grain were below LOQ. No emamectin or emamectin-like residues were found in extractable residues of straw. Results of this study in dicate that significant uptake of emamectin benzoate by rotational cro ps will not occur. Emamectin benzoate residues in soils were not detec ted below the top 0-15-cm segment and are, therefore, unlikely to leac h into groundwater.