Persistence of Organochlorine Insecticides for Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Control in Hawaii

Abstract

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 field plots in Waimanalo on the island of Oahu, Hawaii, and tested periodically for efficacy against the Formosan subterranean termite, Coptotermes formosanus Shiraki. We report the toxicity of aldrin, chlordane, DDT, dieldrin, and heptachlor to C. formosanus 17, 20, 24, 28, and 33 yr after treatment. The degree of penetration of the treated soils by C. formosanus was also measured in laboratory bioassays. After 28 yr, termites tunneled significantly less in soils treated with 0.5% aldrin (in coral and clay), 0.3% dieldrin (in clay), 1.0% heptachlor (in sandy loam), and 2.0% DDT (in coral). None of the insecticides prevented termite penetration 33 yr after application. At label-recommended concentrations, all pesticides except DDT (8.0%) caused high termite mortality up to 28 vr after application. Only 0.5% aldrin, 0.3% dieldrin, and 1.0% heptachlor caused significant mortality after 33 yr. Results of this study should be of value in estimating the risks of termite reinfestation of structures in the tropics and Pacific islands where organochlorine insecticides have been used.