Water molds of the genera Saprolegnia and Leptolegnia are pathogenic to the North American frogs Rana catesbeiana and Pseudacris crucifer, respectively.

Water molds are commonly associated with amphibian mortality. Since water molds often act as saprophytes, it is important to test their effects on amphibians to determine whether they can also act as pathogens. In controlled experiments, the eggs of 2 amphibian species, the American bullfrog Rana catesbeiana and the spring peeper Pseudacris crucifer, suffered higher mortality when they were exposed to zoospores of water molds of the genera Saprolegnia and Leptolegnia, respectively. Water molds are important pathogens in many amphibian systems, yet their ecological impact on amphibians remains mostly unknown.