Thiodan Residues on Corn Plants12

Abstract

The persistence of Thiodan residues was studied on corn plants treated for control of the European corn borer, Pyrausta nubilalis (Hbn.). with a water emulsion formulation of Thiodan at a rate of 1.5 lbs. of Thiodan per acre and a 5% granulated formulation of Thiodan at a rate of 1.0 lb. of Thiodan per acre. Samples of corn were collected during a 9-week period after treatment; these samples were chopped, extracted, and the extracts analyzed for Thiodan by three analytical methods: titrimetric organic chlorine, colorimetric sulfur dioxide evolution, and house fly bioassay. The initial Thiodan residues on the emulsion-treated corn were much higher than on the granular-treated corn. However, from about 1 week after treatment until the experiment was terminated, only slight differences were found in the Thiodan residues resulting from the two treatments. Residues of Thiodan from the granulated formulation persisted on the corn plants as long as or longer than residues from the emulsion formulation. Small but detectable residues persisted longer than 9 weeks after application of both insecticidal formulations.