Just as it did in its imidacloprid pollinator risk assessment, EPA singled out foliar uses of these two chemicals as posing the most risk to honeybees. In particular, foliar applications on cotton fields were categorized as posing high and "likely" risks to pollinators. In contrast, seed treatments for corn, cotton, soybeans and canola were categorized as low risk.

Both clothianidin and thiamethoxam are used primarily as seed treatments, however. The EPA estimated that, on average, 42 million corn acres, 2.1 million soybean acres and 1.3 million wheat acres are treated with clothianidin annually, and 24 million corn acres, 13 million soybean acres, 3 million cotton acres and 2.5 million wheat acres are treated with thiamethoxam each year.

In contrast, just 13% to 14% of thiamethoxam applications each year are foliar or soil applications. Cotton growers account for the bulk of that, with 60,000 pounds a year applied via the soil or foliar sprays. Only around 2% of clothianidin is applied via soil or foliar sprays, with 10,000 pounds a year of that occurring in cotton fields.

IMIDACLOPRID

The EPA's aquatic risk assessment for imidacloprid holds special significance for agriculture, after Canada's Pest Management and Regulatory Agency (PMRA) recently proposed a plan to phase out the insecticide due to its assessment of risks to aquatic insects. (See the DTN story here: http://bit.ly/…).

Overall, EPA concluded that its assessment was "in general agreement with recent findings published by Canada's Pest Management Regulatory Agency and the European Food Safety Authority."

"It is evident... that concentrations of imidacloprid detected in streams, rivers, lakes and drainage canals routinely exceed acute and chronic toxicity endpoints derived for freshwater invertebrates," the agency concluded.

However, the EPA also singled out neonicotinoid seed treatments as the safest application route for imidacloprid, with few risks posed to aquatic invertebrates (which includes insects) from them. Soil and foliar applications posed the most problems, and the agency said it identified "acute and chronic risks" to many freshwater and saltwater invertebrates from those types of applications.

EPA also released its formal responses to the more than 400,000 public comments left on its preliminary pollinator risk assessment for imidacloprid. That initial report alarmed the cotton industry, after EPA concluded that bees are most at risk of exposure to damaging levels of the imidacloprid from foliar and seed treatments in cotton fields.

In its responses, EPA acknowledged that the report had "incorrectly classified cotton pollen as attractive to honey bees" and said "the Agency will update this information in its assessment."

Most relevant to corn and soybean producers was the agency's vow to further investigate the implications of neonicotinoid insecticides "dusting off" seed during planting and infiltrating the pollen or nectar of nearby flowering plants and trees, where bees encounter it.

The agency pointed to a number of steps already underway to study and mitigate this problem: a treated seed stewardship manual by the American Seed Trade Association, industry efforts to offer alternative fluency agents to reduce dust released during planting and new design guidelines from the International Organization of Standards for ag planting equipment aimed at reducing seed dust.

According to EPA, all these risk assessments will be posted to the Federal Register for public comment shortly.

NEW SCHEDULE

Along with its release of neonicotinoid risk assessments, the EPA published an updated schedule for its final registration review of the four chemicals. The agency expects to release initial ecological risk assessments and human health assessments for clothianidin and thiamethoxam in September of 2017. A human health assessment for imidacloprid is also expected in March of 2017.

The agency is ultimately aiming for an interim decision on the registration of neonicotinoids in the spring of 2018, with a final registration decision due the winter of 2018-19.

You can access the revised schedule, the preliminary pollinator-only risk assessments for clothianidin and thiamethoxam and the aquatic risk assessment for imidacloprid here: http://bit.ly/….

Emily Unglesbee can be reached at Emily.unglesbee@dtn.com

Follow Emily Unglesbee on Twitter @Emily_Unglesbee

(PS/AG)

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