CARBONDALE, Ill.—Pesticides routinely used on crops in California have depleted the surrounding frog populations, according to a new study (Environ Toxicol Chem. 2009 Aug;28(8):1696-703) from the Southern Illinois University.
The insecticides most commonly used in the Central Valley, chlorpyrifos and endosulfan, were introduced to the larvae of foothill yellow-legged frogs ( Rana boylii ) in a clinical setting. All R. boylii exposed to concentrations of greater than 0.8 μg/L died before they entered metamorphosis, and half of the population died with 0.3 parts per billion. R. boylii is among the species experiencing severe population declines.
The report found pesticides from the Central Valley of California are transported by winds into the Sierra Nevada Mountains water bodies where amphibians breed.