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

Area of Science:

• Environmental Science
• Ecotoxicology
• Agricultural Science

Background:

• Simultaneous application of genetically modified (GM) Bt corn with neonicotinoid seed coatings (clothianidin) and granular insecticides (tefluthrin) is common in agriculture.
• Understanding the combined ecological impact of these pest management strategies on non-target species is crucial for ecosystem health.

Purpose of the Study:

• To conduct a site-specific ecological risk assessment (ERA) evaluating the combined use of Bt corn, clothianidin, and tefluthrin.
• To determine potential ecological effects on non-target soil and aquatic invertebrates exposed to these agricultural inputs.

Main Methods:

• Field studies and literature review to establish environmental exposure concentrations.
• Acute toxicity bioassays on earthworms (Eisenia fetida), amphipods (Hyalella azteca), and Elmid riffle beetle larvae (Ancyronyx spp.).
• Risk characterization using stressor-response profiles and margin of safety calculations (MOS10).

Main Results:

• No acute toxicity observed in non-target species exposed to senescent Bt corn leaf tissue.
• Clothianidin exhibited large margins of safety, indicating low risk to tested species.
• Tefluthrin demonstrated very low MOS10 values for earthworms and H. azteca, suggesting environmental concentrations may exceed safe levels.

Conclusions:

• Bt corn insecticidal proteins and clothianidin were present at concentrations below ecological effect benchmarks.
• Tefluthrin was frequently detected at levels potentially toxic to non-target organisms, particularly if it disperses off-site.
• The combination of these insecticides did not result in increased toxicity compared to individual exposures.