Effects of field application levels of wildfire control chemicals, Phos-Chek? G75-F (PC) and Silv-Ex? (SE), were examined on red-winged blackbird (Agelaius phoeniceus) embryos. Embryos were more sensitive to PC and SE when eggs were immersed for 10 s at an early developmental stage (days 3?5 of incubation) than at a later stage (days 6?9 of incubation). The LC50 (concentration causing 50% mortality) for early stage embryos exposed to PC was 213.3 g/L (slope = 1.6; 95% confidence interval [CI] = 129.1?326.1). The no observed effect concentration (NOEC) was below 135 g PC/L, which caused a significant increase in embryonic mortality and represents the lowest field coverage level of 1 gal/100 feet2. The LC50 for early stage embryos exposed to SE was 19.8 g/L (slope = 1.5; 95% CI = 11.7?52.2). Significant mortality was observed at 10 g SE/L and marginal at 7.5 g SE/L with an apparent NOEC around 5 g SE/L. Neither chemical resulted in apparent developmental malformations. Embryos of songbirds are potentially at risk from the wildfire control chemicals, Phos-Chek? G75-F and Silv-Ex?.
Additional publication details
Effects of Phos-Chek? G75-F and Silv-Ex? on red-winged blackbird (Agelaius phoeniceus) embryos