PERSISTENCE OF ORGANOCHLORINE INSECTICIDES FOR FORMOSAN SUBTERRANEAN TERMITE (ISOPTERA, RHINOTERMITIDAE) CONTROL IN HAWAII

In a long-term field test, five organochlorine soil insecticides were applied at two concentrations to crushed coral, Catano sandy loam, or Waimanalo silty clay. The treated soils were weathered in exposed fiel d plots in Waimanalo on the island of Oahu, Hawaii, and tested periodi cally for efficacy against the Formosan subterranean termite, Coptoter mes formosanus Shiraki. We report the toxicity of aldrin, chlordane, D DT, dieldrin, and heptachlor to C. formosanus 17, 20, 24, 28, and 33 y r after treatment. The degree of penetration of the treated soils by C . formosanus was also measured in laboratory bioassays. After 28 yr, t ermites tunneled significantly less in soils treated with 0.5% aldrin (in coral and clay), 0.3% dieldrin (in clay), 1.0% heptachlor (in sand y loam), and 2.0% DDT (in coral). None of the insecticides prevented t ermite penetration 33 yr after application. At label-recommended conce ntrations, all pesticides except DDT (8.0%) caused high termite mortal ity up to 28 vr after application. Only 0.5% aldrin, 0.3% dieldrin, an d 1.0% heptachlor caused significant mortality after 33 yr. Results of this study should be of value in estimating the risks of termite rein festation of structures in the tropics and Pacific islands where organ ochlorine insecticides have been used.