Evaluating mosquito control pesticides for effect on target and nontarget organisms

Recent requirements for biomonitoring of urban stormwater runoff have raise d the issue of toxic contributions from mosquito control products. A compar ison of seven pesticides for their toxicity to target and nontarget organis ms was conducted in field and laboratory trials to determine relative impac ts in and around Craighead County, Arkansas. Twenty-four and forty-eight-ho ur acute toxicity tests using Ceriodaphnia dubia, Daphnia magna, Daphnia pu lex, and Pimephales promelas were employed with U.S. Environmental Protecti on Agency (U.S. EPA) suggested procedures as standard test organisms. Addit ional tests with resident mosquito fish, Gambusia affinis, and mosquito lar vae, Anopheles quadrimaculatus, included ditch-receiving waters to compare the somewhat sterile laboratory exposures to actual field conditions. Expos ure to as much as 31.4 mu g/L of the pesticides Dursban(R), malathion, Perm anone(R), Abate(R), Scourge(R), B.t.i, and Biomist(R) were required for eff ective control of An. quadrimaculatus, whereas as little as 2.7 mu g/L resu lted in substantial mortality of some nontarget organisms. These data sugge st that prevailing application rates for effective mosquito control not onl y affect nontarget organisms but may also confound stormwater and nonpoint toxicity evaluations that utilize sensitive indicator species.