Toxicity of emamectin benzoate to mallard duck and northern bobwhite quail

Nineteen- to 26-week-old mallard ducks (Anas platyrhynchos) were found to be more sensitive than northern bobwhite quail (Colinus virginianus) of the same age to single oral doses of emamectin benzoate. The resulting median lethal dose values determined for emamectin benzoate to mallard duck and northern bobwhite quail were 76 and 264 mg/kg, respectively, and the no-observed-effect levels were <25 and 25 mg/kg, respectively. Exposure of 10-d-old mallard ducks and bobwhite quail to emamectin benzoate in feed also gave relatively high median lethal concentration (LC50) values of 570 and 1,318 ppm, respectively, and no-observed-effect concentrations of 20 and <125 ppm, respectively. Clinical signs of toxicity included lethargy, ruffled appearance, loss of righting reflex, and reduction in food consumption; these signs appeared to be fully reversible with cessation of exposure. The maximum residue level of emamectin benzoate found in field-treated foliage is several-fold (7,125–16,475) less than these LC50 values. Because the likely primary route of emamectin benzoate exposure to birds is through treated food in the diet, these results indicate minimal acute risk to avians from emamectin benzoate use in crop protection.