The California red-legged frog (CRLF) (Rana aurora draytonii) is endemic to California and Baja, Mexico. The species has been extirpated from 70% of its former range and was listed as threatened under the Endangered Species Act in 1996. The US Environmental Protection Agency must determine whether 66 pesticides currently authorized for use in California may adversely affect the CRLF. A screening-level and refined effects determination (ED) was conducted for the CRLF to assess potential direct and indirect effects associated with exposure to the insecticide dimethoate. Our screening-level ED indicated that dimethoate poses negligible risks to CRLFs or to the habitat and algal prey upon which they depend. A subsequent refined probabilistic ED indicated that dimethoate has a low probability of adversely affecting aquatic invertebrate prey of the CRLF. Thus, label uses of dimethoate in California are unlikely to adversely affect CRLFs, their prey, and their habitat.

Refined effects determination for the California red-legged frog (<i>Rana aurora draytonii</i>) potentially exposed to dimethoate

248th National Meeting (2014)

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Refined effects determination for the California red-legged frog (Rana aurora draytonii) potentially exposed to dimethoate