Widespread triazole pesticide use affects infection dynamics of a global amphibian pathogen

The sixth mass extinction is a consequence of complex interplay between multiple stressors with negative impact on biodiversity. We here examine the interaction between two globally widespread anthropogenic drivers of amphibian declines: the fungal disease chytridiomycosis and antifungal use in agriculture. Field monitoring of 26 amphibian ponds in an agricultural landscape shows widespread occurrence of triazole fungicides in the water column throughout the amphibian breeding season, together with a negative correlation between early season application of epoxiconazole and the prevalence of chytrid infections in aquatic newts. While triazole concentrations in the ponds remained below those that inhibit growth of Batrachochytrium dendrobatidis, they bioaccumulated in the newts' skin up to tenfold, resulting in cutaneous growth-suppressing concentrations. As such, a concentration of epoxiconazole, 10 times below that needed to inhibit fungal growth, prevented chytrid infection in anuran tadpoles. The widespread presence of triazoles may thus alter chytrid dynamics in agricultural landscapes.

Automated summary

The sixth mass extinction is caused by various negative impacts on biodiversity. This study examines the interaction between two widespread factors contributing to amphibian declines: the fungal disease chytridiomycosis and the use of antifungal agents in agriculture. Field monitoring in agricultural landscapes shows the presence of triazole fungicides in amphibian ponds, and the application of epoxiconazole correlates negatively with chytrid infections in newts. Although the triazole concentrations in the ponds do not inhibit the growth of Batrachochytrium dendrobatids, they accumulate in the newts' skin, resulting in growth-suppressing concentrations. Consequently, a concentration of epoxiconazole, even ten times lower than the growth-inhibiting level, prevents chytrid infection in anuran tadpoles. The widespread presence of triazoles may therefore alter chytrid dynamics in agricultural landscapes.