DDT RESIDUES IN FRUIT, FOLIAGE, AND SOIL OF A VINEYARD FOLLOWING A STANDARD INSECT CONTROL PROGRAM

Abstract

Residues of p,p′-DDT, o,p′-DDT and p,p′-DDE on grape foliage and fruit sampled before and after each of four applications of DDT 50% wettable powder at 3.4–4.5 kg/ha (3–4 lb/acre) and at harvest were investigated by gas chromatography. DDT residues on fruit at harvest, 54 days after the last spray, ranged from 0.15 to 0.87 ppm depending on the grape cultivar. More than 99% of residual DDT was found in skins. A very small amount (less than 0.1 ppm) of DDT in all aerial parts of the vines may have been absorbed from the soil containing 2.3–4.1 ppm DDT. Residues from spray drift were found in the control plot after every application in the sprayed plot, but they were only about 0.12% of the level found in the latter plot. The half-life of DDT based on the conversion of p,p′-DDT to p,p′-DDE on the surface of the leaves and fruit is discussed.