Dermal fungicide exposure at realistic field rates induces lethal and sublethal effects on juvenile European common frogs (Rana temporaria)

Viticulture is one of the most pesticide-intensive agricultures in Europe leading to a spatio-temporal overlap of amphibian migration and pesticide applications. Since post-metamorphic, terrestrial amphibian stages are mostly neglected in ecotoxicological studies, we investigated acute effects of viticultural fungicides on juvenile common frogs (Rana temporaria). Tadpoles from an uncontaminated pond were placed in enclosures in eight ponds with an increasing degree of pesticide contamination in southwest Germany to represent different aquatic exposure backgrounds. After metamorphosis, juveniles were exposed to soil contaminated with 50% of the recommended field rates of the fungicides Folpan® 80 WDG and Folpan® 500 SC with the same amount of folpet as active ingredient and differing additives. After 48 hours, effects on the survival, body mass and behavior were investigated. No effect of the aquatic exposure background on the terrestrial sensitivity could be detected. The acute terrestrial exposure lead to mean mortality rates of 14% (13 - 17%, SC) and 60% (17 - 100%, WDG) and resulted in adverse effects on locomotor activity as well as feeding behavior. Moreover, the results suggest that the toxicity of the two tested folpet formulations depends on their additives. Since the identified effects may result in severe impairments and thus in declines of amphibian populations, a more protective risk assessment of pesticides is needed for post-metamorphic amphibians to ensure proper conservation of amphibian populations. This article is protected by copyright. All rights reserved.