John Wiley & Sons, Ltd.

A site‐specific ecological risk assessment for corn‐associated insecticides

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Courtesy of John Wiley & Sons, Ltd.

A site‐specific ecological risk assessment (ERA) was conducted to examine the simultaneous use of genetically modified corn (Bt corn) with a neonicotinoid seed coating, clothianidin, and use of a granular insecticide, tefluthrin, to protect crops from pest damage. A field study was conducted on‐site and exposure data from the literature was summarized to determine the matrices and exposure concentrations non‐target species could typically experience within an agricultural ecosystem. To determine ecological effects to non‐target species, acute toxicity bioassays were conducted on earthworms (Eisenia fetida), amphipods (Hyalella azteca), and Elmid riffle beetle larvae (Ancyronyx spp.) in which the test species were exposed to single insecticides as well as the mixture of the three insecticides. In the risk characterization section of the ERA, stressor‐response profiles for each species tested were compared to field distributions of the insecticides and a margin of safety at the 10th percentile (MOS10) was calculated to estimate risk. No acute toxicity was observed in any of the three non‐target species when exposed to senescent Bt corn leaf tissue. Large MOS10 values were calculated for clothianidin to the non‐target species. When bioassays were compared to tefluthrin field distributions, very low MOS10 values were calculated for earthworms (0.06) and H. azteca (0.08) due to the environmental concentrations often exceeding the stressor‐response profile. There was no increased toxicity observed when non‐target species were exposed to a mixture of the three insecticides. In summary, the genetically modified corn insecticidal proteins and clothianidin were not found at environmental concentrations exceeding benchmark values for ecological effects, but tefluthrin was consistently detected in the environment at levels that could be causing toxicity to non‐target species, especially if it is able to travel off‐site. This article is protected by copyright. All rights reserved

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