Differential sensitivity of developmental stages of the South American toad to a fungicide based on fludioxonil and metalaxyl-M

GABRIELA SVARTZ; MERCEDES ACQUARONI; CRISTINA PÉREZ-COLL

ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH

SPRINGER HEIDELBERG

Lugar: HEIDELBERG; Año: 2018 vol. 25 p. 23857 - 23863

0944-1344

Agricultural fungicide application in Argentina has increased twice since 2008, with Maxim® XL (2.5% Fludioxonil + 1% Metalaxyl-M) as one of the most used fungicide formulation. The toxicity of this pesticide on Rhinella arenarum was assessed by means of continuous (from embryo and larval development) and 24-h pulse exposure standardized bioassays. Lethality was concentration- and exposure time-dependent. Maxim® XL caused a progressive lethal effect along the bioassays with higher toxicity on embryos than larvae, obtaining LC50s at 96, 336 and 504 h of 10.85, 2.89 and 1.71 mg/L for embryos, and 43.94, 11.79 and 5.76 mg/L for larvae respectively. Lethal 504-h NOEC values for embryos and larvae were 1 and 2.5 mg/L respectively. A stage-dependent toxicity of Maxim® XL was also demonstrated within the embryo development, with early stages more sensitive than the later ones, and blastula as the most sensitive developmental stage. The risk quotients obtained for chronic risk assessment determined a potential threat for the survival and continuity of R. arenarum populations under these conditions. The results indicate that the levels of the fungicide reaching amphibian habitats could be risky for the early development of this amphibian species. This study also emphasizes the necessity to evaluate the chronic effects of fungicides in pesticide risk assessment.