A primary factor contributing to amphibian declines is the application and accumulation of agricultural chemicals. We examined how a common fungicide, chlorothalonil, affects development in larval northern leopard frogs (Lithobates pipiens) in conjunction with atrazine and increased nitrate concentrations in laboratory containers. No synergistic or antagonistic interactions between the treatments were identified. Further, there was no significant difference in weight and Gosner stage between tadpoles exposed to different chlorothalonil concentrations. However, nitrate increased tadpole mortality and decreased growth. According to our results, environmentally relevant concentrations of chlorothalonil may not be directly toxic to leopard frogs but may indirectly influence development.
