Loss of Activity of Chlorinated Hydrocarbon Insecticides in Soil as Measured Against the Eye Gnat, Hippelates collusor1

Abstract

The long-term effectiveness of DDT, endrin, lindane, dieldrin, aldrin and Shell Development Company Compound SD-4402 (1,3,4,5,6,7,8,8-oetachloro-3a-4,7,7a-tetrahydro-4, 7-methanophthalan) in soil was studied under controlled conditions against the eye gnat, Hippelates collusor (Townsend). Several lots of Coachella fine sand containing 0.15% organic matter dry weight basis Were treated with sprays of each toxicant and stored in gallon mayonnaise jars in a glasshouse, maintained at 88±2° F. The moisture content of the soil was maintained at 11% to 12% of the dry weight of the soil. The dosage of each material was adjusted to the initial LD90 level of activity. The activity of the toxicants was determined by bioassaying lots of the treated soil against the gnat at 3-month intervals. No loss of activity was detected for DDT, endrin and lindane, 9 months after storage. Dieldrin also did not show loss of activity 12 months after start of the storage period under the test conditions. Aldrin and compound SD-4402 manifested appreciable loss of activity 3 months after start of the storage period. After the 3-month storage period 53% of aldrin and 40% of compound SD-4402 were not accounted for. The magnitude of loss of aldrin further increased on storage and was determined to be 77% after a period of 9 months of storage and 70% after 12 months of storage. The loss of activity of compound SD-4402 increased rapidly from after the 3-month to the 6-month interval of storage and was determined to be 72% after a period of 6 months of storage. No further increase in loss of this material and of aldrin could be detected with the bioassay method used in these studies.