Insecticidal Residues in Cucumbers and Alfalfa Grown on Aldrin- or Heptachlor-Treated Soils1

Cucumbers were grown in 1962 and 1963 on Carrington silt loam soils which contained various amounts of aldrin or heptachlor residues. The experiment provided that some of the developing cucumber fruits were lying on the ground while others developed without touching the soil. Similar insecticidal residue concentrations were found in all these cucumbers, as well as in the lower halves as compared with the upper halves of fruits lying on the ground. Insecticidal residues apparently penetrated through the root system and were then translocated into the cucumber fruits. Third cuttings of fresh alfalfa, grown in 1964 on aldrinor heptachlor-treated soils, were analyzed by gas-liquid chromatography and bioassay procedures. No mortalities were obtained with vinegar flies, Drosophila melanogaster Meigen, during a 48-hr exposure period to purified extracts of alfalfa from soils that contained 0.2–0.7 lb/6-in. acre of aldrin and dieldrin or heptachlor and heptachlorepoxide (2,3 epoxy-1,4,5,6,7,8,8-heptachloro-3a,4,7,7a-tetrahydro- 4,7-methanoindene) residues. Extracts of 70–100 g of alfalfa grown on soils of higher insecticidal residue concentrations were toxic to the insects and also contained measurable amounts of these chemicals. Residue concentrations in or on alfalfa grown on aldrin-treated soils were 0.88% ± 0.23 of their concentrations in the soil at harvest time, and 3.01% ± 0.85 for alfalfa grown on heptachlor-treated soils.