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.

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

Disappearance of monocrotophos from flue-cured tobacco was studied at three locations (Kinston, Clayton, and Reidsville, North Carolina) in 1973. Average residues on green tobacco leaves collected immediately after application were 41 and 84 ppm, respectively, for application rates of 0.56 and 1.12 kg/ha. Levels declined to about 18 and 40 ppm for the two rates three days after application, to about 9 and 23 ppm at five days, and to about three and eight ppm at nine days. Conventional curing reduced residues on flue-cured tobacco by at least 99%.