Effects of weathering and flue-curing on methomyl residues on tobacco.

A replicated field experiment was conducted at two locations to determine the disappearance of methomyl from flue-cured tobacco. Immediately after application, methomyl residues were 88 and 113 ppm at Clayton and 44 and 105 ppm at Reidsville, respectively, for 0.56 and 1.12 kg/ha application rates. After 5 days these levels dropped to 0.7 and 2.8 ppm at Clayton and 1.4 and 4.1 ppm at Reidsville. At 9 days after application, 99% of the methomyl had disappeared at both locations. Losses of methomyl during flue-curing averaged 96% over locations, rates of application, and times of harvest, compared to an average loss of 98% due to weathering in the field for 5 days. The disappearance of methomyl during the curing process was approximately the same for both locations.