Residual Nature of Endosulfan in Burley Tobacco 1

Burley tobacco harvested immediately after treatment with 0.5 Ib/acre of endosulfan and cured for four months contained average total endosulfan residues of 23.2 ppm. Residue levels in the top, middle, and bottom leaves were 49.6, 13.2, and 6.7 ppm, respectively. On the top leaves, endosulfan I comprised 13 percent, endosulfan II 78 percent and endosulfan sulfate 9 percent of the total. The sulfate accounted for approximately 20 percent of the total residues on the middle and bottom leaves, with a corresponding decrease in the concentration of endosulfan II. When the time between treatment and harvest was increased to 28 days, the average total residues on the cured tobacco was 2.2 ppm, with almost equal quantities on top, middle, and bottom leaves. Treatment at 42 and 70 days prior to harvest resulted in 0.64 and 0.34 ppm total residues and 1.15 and 0.41 ppm highest residues in the bottom leaves. Comparing the levels of residues in freshly harvested tobacco with those in cured tobacco showed that the loss during curing decreased as the time between treatment and harvest increased to 14 days (53 percent loss), but remained constant thereafter.