Fate and effects of two pesticide formulations in the invertebrate Folsomia candida using a natural agricultural soil

The present work was financially supported by the Portuguese Foundation for Science and Technology (FCT) through the projects UID/MAR/04292/2013, ENVIRONOME (PTDC/AGR-PRO/3496/2012- POCI-01-0145-FEDER-016773), and grants awarded to TS (SFRH/BD/ 98266/2013), SN (SFRH/BPD/94500/2013), and TNL (SFRH/BPD/ 110943/2015). Project was also partially funded by the Integrated Programme of SR&TD “SmartBioR” (reference Centro-01-0145-FEDER000018) co-funded by Centro 2020 program, Portugal2020, European Union, through the European Regional Development Fund.

Degradation rates of two widely used pesticides were assessed, and acute and chronic effects on a standard invertebrate species investigated. An herbicide (Montana®) and fungicide (Bravo500®) formulations were investigated and results were compared to the isolated active substances of each formulation (glyphosate and chlorothalonil, respectively). Tests were performed using the invertebrate Folsomia candida as test species and an agricultural natural soil. Degradation rate tests were determined under aerobic conditions at 20 ± 2 °C, using an ecologically relevant concentration of 5 mg (a.i.) kg−1 of soil for both chemicals. Results demonstrated degradation half-lives (DT50) of 2.2 days for Montana® and 2.8 days when pure glyphosate was tested. Values of 1.1 and 2.9 days were registered for Bravo500® and its active substance chlorothalonil, respectively. There were no effects on survival for the tested concentrations of both forms of the herbicide (up to 17.3 mg kg−1). However, reproduction was affected, but only by the herbicide formulation, with an estimated EC50 value of 4.63 mg (a.i.) kg−1. Effects were most unlikely related to glyphosate. For chlorothalonil, both tested forms affected survival and reproduction. The estimated LC50 values were 117 mg (a.i.) kg−1 and 73.5 mg (a.i.) kg−1, and the EC50 41.3 mg (a.i.) kg−1 and 14.9 mg kg−1 for the formulation and the active ingredient, respectively. The effects of the active ingredient were significantly stronger, indicating the major influence of the active substance in the effects caused also by the formulation. Overall results demonstrate the importance of evaluating the effects of the formulated chemicals, as they are applied in the field, and not only their isolated active ingredients.

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