Avermectin B sub 1a metabolism in celery: A residue study

Radioactivity equivalent to less than 4% of the total avermectin B{sub 1a} applied to mature and immature celery as a mixture of unlabeled and ({sup 14}C)- or ({sup 3}H) avermectin B{sub 1a} remained in harvested plants. The half-lives of radiolabeled avermectin B{sub 1a} residues as measured by the dissipation of total {sup 3}H radioactivity from celery parts ranged from 5.2 to 12.9 days in celery treated at 0.01 and 0.10 lb of AI/acre. The percentage of total radioactivity in celery parts readily extractable with acetone (range of 57.8-97.1%) generally decreased with increasing postharvest intervals. High-performance liquid chromatography of acetone extracts of celery leaves and stalks produced four discernible peaks of radioactivity, designated as polar metabolites, moderately polar metabolites, avermectin B{sub 1a}, and the {Delta}{sup 8,9} isomer of avermectin B{sub 1a}. The percentage of acetone extract radioactivity represented by polar metabolites generally increased with increasing postharvest intervals.