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Uptake of emamectin benzoate residues from soil by rotational crops

Chukwudebe, A.C., Feely, W.F., Burnett, T.J., Crouch, L.S., Wislocki, P.G.
Journal of agricultural and food chemistry 1996 v.44 no.12 pp. 4015-4021
abamectin, insecticide residues, Daucus carota, grain crops, Hordeum vulgare, barley straw, Lactuca sativa, crop rotation, sandy loam soils
Radiocombustion analyses of barley, carrots, and lettuce planted in 30, 120, 141, and 365-DAT plots after applications of the test compound [14C]4''-deoxy-4''-epi-methylaminoavermectin B1a ([14C]MAB1a; 0.1008 kg ai ha-1) demonstrated that total residues in edible lettuce and carrots were below the limits of quantitation (LOQ; <4 micrograms/kg). Highest residue levels of 16 and 30 micrograms/kg were found respectively, in 30- and 141-DAT plot barley straw. In both straw samples, percentages of extractable and unextractable radioactivity were similar, averaging 54 and 46%, respectively, of total radioactivity. Cellulase/hemicellulase digestions of resulting marcs indicate that some radioactivity was incorporated into plant natural products. Extractable residues in straw and grain were below LOQ. No emamectin or emamectin-like residues were found in extractable residues of straw. Results of this study indicate that significant uptake of emamectin benzoate by rotational crops will not occur. Emamectin benzoate residues in soils were not detected below the top 0-15-cm segment and are, therefore, unlikely to leach into groundwater.