Canadian Forest Service Publications

Laboratory and field exposure of two species of juvenile amphibians to a glyphosate-based herbicide and Batrachochytrium dendrobatidis. 2013. Edge, C.B.; Gahl, M.K.; Thompson, D.G.; Houlahan, J.E. Science of the Total Environment 444:145-152.

Year: 2013

Issued by: Great Lakes Forestry Centre

Catalog ID: 34350

Language: English

Availability: PDF (request by e-mail)

Available from the Journal's Web site.
DOI: dx.doi.org/10.1016/j.scitotenv.2012.11.045

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Abstract

Herbicides are commonly used in agriculture and silviculture to reduce interspecific competition among plants and thereby enhance crop growth, quality, and volume. Internationally, formulations of glyphosate-based herbicides are the most widely used herbicides in both these sectors. A large amount of work has focused on the effects of these herbicides on amphibians. Several laboratory and mesocosm studies have demonstrated that various formulations of glyphosate herbicides can be acutely toxic to larval and juvenile amphibians at concentrations at the upper end of environmental realism. However, to date there has been little work done investigating such effects in natural systems, limited work on juvenile amphibians, and only a few studies have investigated interactions with other stressors. We conducted a 16. day field experiment in which juveniles of two amphibian species (Lithobates clamitans and Lithobates pipiens) were exposed to the herbicide Roundup WeatherMax™ at four application rates (0, 2.16, 4.32 and 8.64. kg a.e./ha) to investigate effects on survival, liver somatic index (LSI), body condition, and incidence of disease caused by Batrachochytrium dendrobatidis (Bd). In a separate 16. day laboratory experiment, we exposed juvenile L. clamitans to both the herbicide and Bd. Results of our studies showed that this particular herbicide formulation had no effect on juvenile survival, LSI, body condition, or disease incidence, nor was there an interaction between exposure to herbicide and exposure to the disease in tests which closely mimic real world exposure scenarios. These experiments suggest that Roundup WeatherMax as typically used in agriculture is unlikely to cause significant deleterious effects on juvenile amphibians under real world exposure conditions.

Plain Language Summary

The goal of this study was to test the effects of the glyphosate-based herbicide Roundup WeatherMaxTM, commonly used in agriculture, on two species of juvenile frogs. We applied the herbicide under field conditions at exposure levels ranging from environmentally realistic to extreme worst case scenarios as high as 8.63 kg active ingredient per hectare. We exposed green frogs and northern leopard frogs to four herbicide application rates during a 16-day field trial. Results showed no effects on survival, liver somatic index (LSI), body condition or disease incidence. In a separate laboratory experiment we exposed frogs to both the herbicide and to the fungus Batrachochytrium dendrobatidis (Bd), known to cause a disease common in frogs. Our results showed no interaction between exposure to herbicide and exposure to the disease. These experiments suggest that Roundup WeatherMaxTM as typically used in agriculture is unlikely to cause significant deleterious effects on juvenile amphibians under real world exposure conditions.