Nature: 30 October 2008

Declining amphibian populations have been reported in the past twenty years from locations all over the world. These events have been attributed variously — often without much evidence — to habitat loss, climate change and disease. Now a case study of the northern leopard frog, Rana pipiens, in wetlands across Minnesota points to the use of agrochemicals — combined with parasitic infestation — as a contributor to population decline. The study sought factors associated with the abundance of larval trematodes in the frogs. An abundance of these parasites can be debilitating, causing limb malformation, kidney damage and death. Of more than 240 plausible predictors of trematode infection — ranging from the presence of various plant and animal species to agrochemicals and habitat geography — two stood out: the herbicide atrazine and the fertilizer, phosphate.
Atrazine and phosphate are principal agrochemicals for corn and sorghum production, and together they accounted for 74% of the variation in trematode abundance.

http://www.nature.com/nature/journal/v455/n7217/edsumm/e081030-12.html