Confined hen pheasants (Phasianus colchicus) were exposed to simulated field applications of COUNTER 15G? Soil Insecticide (S-[[1,1-(dimethylethyl) thio]methyl] 0, 0-diethyl phosphorodithioate), a short-lived organophosphate compound, during July and August 1973. The hens exposed to COUNTER at dosage rates of both 468 g (1.03 lb) and 2,340 g (5.15 lb) of technical material per acre did not suffer from either acute or chronic organophosphate poisoning nor did they accumulate measurable residues of COUNTER or its metabolites. These findings suggested that field applications of COUNTER, in spring, at the recommended dosage rate of 454 g (1 lb) of technical material per acre would not be a serious depressant to resident populations of pheasants. J. WILDL. MANAGE. 39(1):174-178 COUNTER 15G@ Soil Insecticide, a registered trademark of American Cyanamid Company, is an organic phosphate compound developed to control corn rootworm infestations in the United States. A granular (0.297 < diam < 0.710 mm) insecticide, COUNTER contains 15 percent technical material. The recommended application rate is 227 g (8 ounces) of COUNTER 15G per 304.8 m (1,000 ft) of corn row, which is equivalent to dosage rates of 445 and 468 g (0.98 and 1.03 lb) of technical material per acre for 101.6and 96.5-cm (40and 38-inch) row spacings, respectively. COUNTER is applied in a 17.8-cm (7-inch) band on the soil surface over the corn row; the granular insecticide is dropped onto the soil behind the planter shoe but in front of the press wheel of the planter, and thus is pressed, but not incorporated, into the upper soil surface. COUNTER is rapidly and extensively biodegraded in soil, plants, and animals. Its solubility in water is only 10-15 ppm. The half-life of the parent compound and of its total group of metabolites, as determined out-of-doors in sandy loam soils and indoors in silt loam soils, was about 2 weeks and 11 weeks, respectively (H. H. Nau, personal communication). COUNTER, therefore, has less environmental persistence than any organochlorine insecticide and even less persistence than many organophosphate compounds (Edwards 1972). Like other organophosphate insecticides, COUNTER is a neurotoxicant that inhibits enzyme cholinesterase activity. As an acute poison, COUNTER is more toxic than many organophosphate and organochlorine insecticides (Hayes 1963); technical COUNTER has an oral LD50 of 9.0 mg/kg in female white rats and a dermal LDo0 of 1.1 mg/kg in male albino rabbits. Acute symptoms of organophosphate poisoning generally emerge within 2 to 72 hours after exposure to the chemical. Animals that survive the acute stage of organophosphate poisoning usually recover if subsequent exposure to the chemical is prevented. The rapid biological degradation of organophosphates generally renders them less toxic than organochlorines as chronic poisons. To illustrate, Fletcher (1972, Reps. J1777 and J1778, Industrial BIO-TEST Laboratories, Inc., Northbrook, Illinois) found, in 8-day feeding trials, that dietary median lethal concentrations (LC50) of COUNTER and dieldrin were 145 ppm and 31 ppm, respectively, for 2-week-old pheasant chicks, and 185 ppm and 62 ppm, 174 J. Wildl. Manage. 39(1):1975 This content downloaded from 207.46.13.111 on Sun, 22 May 2016 05:23:46 UTC All use subject to http://about.jstor.org/terms PHEASANT RESISTANCE TO AN INSECTICIDE Labisky 175 respectively, for 2-week-old mallard (Anas platyrhynchos) ducklings. This investigation was designed to ascertain selected physiological responses of confined hen pheasants to simulated field applications of COUNTER 15G Soil Insecticide at 1.03 and 5.15 lb of technical material per acre. The study was supported, in part, by a grant from American Cyanamid Company. I thank W. L. Anderson, G. C. Sanderson, J. W. Sanderson, and H. C. Schultz, all of the Illinois Natural History Survey, for technical or editorial assistance, or both. H. H. Nau, American Cyanamid Company, Princeton, New Jersey, expedited the study in numerous ways. The Max McGraw Wildlife Foundation, Dundee, Illinois, generously provided the pheasants for the investigation.