Journal of the American Mosquito Control Association, 15(4):453-457, 1999 Copyright O 1999 by the American Mosquito Control Association, Inc. CHLORAMINE AND COPPER SULFATE AS CONTROL AGENTS OF PLANKTONIC LARVAE OF CHIRONOMUS LURIDUS IN WATER SUPPLY SYSTEMS M. HALPERN,T A. GASITH,, B. TELTSCH,T R. PORAT3 eNp M. BROZAT ABSTRACT. The latest approach to control of midge larvae in drinking-water supplies is suppression of the planktonic lst-stage larvae, by using 2 disinfectants, chloramine and copper sulfate. The median lethal concen- tration for 24-h exposure of the lst-stage larvae of Chironomus luridus to chloramine and copper sulfate indi- vidually was 0.51 and 0.38 mg/liter, respectively. The increase of copper sulfate to 0.5 mg of copper per liter to water containing chloramine (0.5 mg/liter) created a synergistic reaction that resulted in 96Vo (+87o SD) mortality of the planktonic larvae. This treatment may serve as an effective control of lst-stage larvae in municipal drinking-water supplies. KEY WORDS Chironomidae, midge control, water supply, chloramine, copper sulfate INTRODUCTION In the early 1990s, the Israeli Water Company began receiving complaints of "red worms" in mu- nicipal drinking-water supplies. Investigation of the water distribution system revealed that a maiority of the covered storage tanks receiving Lake- Kin- neret (Sea of Galilee) water via the Israeli National Water Carrier were infested with chironomid midg- es, mostly of the genus Chironomus (Freidberg et al. 1995). The infestation involved all developmen- tal stages and the populations peaked during the summer and autumn. Infestation of drinking-water systems had been previously reported in Germany (Kruger 1941), the United Kingdom (Kelly 1955, Williams 1974), and,the USA (Bay 1993, Alexan- der et al. 1997). Apparently the problem is more widespread than previously recognized in the sci- entific literature. In the United Kingdom, for ex- ample, where water is taken from rivers. chirono- mid infestation in drinking-water distribution systems is quite common (P van Poppelen, person- al communication). Adult chironomids are medically important be- cause they cause allergic reactions (Cranston 1995). The larvae have not been found to cause disease or other deleterious effects in humans (Gerardi and Grimm 1982; Ali 1991, 1995). However these lar- vae are serious water-quality nuisances in man- made lakes (Mulla et al. 1976) and in municipal potable-water systems. Broza et al. (1998) described a protocol for ef- ficient control of sedentary last-stage midge larvae in covered storage tanks ofthe water supply system in Israel by applying high doses of chloramine (shock chloramination) for a short period in tem- 'Department of Biology, University of Haifa at Oran- im, Tivon 36006, Israel. 2Institute for Nature Conservation Research, George S. Wise Faculty of Life Sciences, Tel Aviv Universitv. Ra- mat-Aviv 69978, Israel. 3 Mekorot Water Company, Central Water euality Lab- oratory, Nazareth Illit 17105, Israel. porarily disconnected tanks. In the present study, we examine an alternative approach to the control of the planktonic stage of midge larvae by applying a chronic low concentration of chloramine and cop- per sulfate. Both these chemicals are permitted for use as control agents in drinking water in Israel. The permissible ranges of chloramine and copper for Israeli consumers are 0.75 and 1.4 mg/liter, re- spectively (National Health Regulations 1995). Newly hatched midge larvae leave the egg mass and remain planktonic until a suitable habitat for tube building is found (Oliver 1971). We hypothe- sized that the newly hatched larvae would be more sensitive to chloramine and copper than the other stages and that the 2 chemicals, even in low con- centrations, could have a synergistic effect. Control of the planktonic stage would prevent buildup of midge populations. The effect of copper on chironomid larvae has been relatively well studied (e.g., Rosenberg 1993, Lindegaard 1995). Most of the studies analyzed the effect of copper and other heavy metals on natural and laboratory populations in polluted water. The uptake of copper by chironomid larvae and its fate during metamorphosis were studied by Timmer- mans et al. (1992), Timmermans and Walker (1990), and Watts and Pasco fl996). The latrer showed significant growth reduction of larvae ex- posed to 2 formulated reference sediments at cop- per concentrations of 3 and, 4 mg Cu2+/liter- Stu- ljfzand et al. (1996) showed a negative effect of copper at 0.006-0.06 mg/liter on the growrh of lst- stage larvae. Copper hydroxyl and cupric ions, which are the toxic forms of copper, can penetrate into the body through the gut or across the body surface (Koswalt and Knight 1987a,1987b). The effect of chloramine on chironomide larvae was not studied before the work of Broza et al. (1998). In invertebrates exposed to chloramine, sublethal physiologic effects include reduction in food filtration rates, decrease in egg production in copepods and rotifers, and decreased rates of res- piration and growth in the larvae of the American