The debate over neonicotinoids’ impacts on the environment continues to rage, as evidenced by comments submitted to EPA as part of the agency’s review of the most widely used insecticides on the planet.

Manufacturers, farmers, environmentalists and lawmakers all weighed in by the April 21 deadline, not just on environmental impacts, but also on the benefits of neonics in cotton and citrus. The EPA assessments are part of the agency’s registration review process for neonics, expected to be completed by the end of this year.

Not surprisingly, opinions varied. Neonic makers Bayer CropScience and Syngenta questioned the data EPA used to evaluate the risks of their products to birds and mammals. Bayer makes clothianidin (Poncho), Syngenta makes thiamethoxam (Cruiser), and Bayer and Valent manufacture imidacloprid (Gaucho).

Syngenta, for example, said that EPA’s concerns for birds and mammals eating seeds treated with thiamethoxam should be tempered by the knowledge that most seeds cannot be consumed because they’re below the surface.

“Syngenta’s position is that the overall probability of adverse effects to birds and mammals due to chronic consumption of thiamethoxam-treated seeds is very low after considering realistic estimates of the proportion of treated seeds in bird and mammal diets (and) reduction of exposure based on a seed incorporation rate of 99 percent, with only 1 percent of planted seeds available for consumption by wildlife,” among other reasons.

Thiamethoxam is used as a seed treatment in a number of crops, including corn, sunflower, oilseed rape, sugar beets, soybeans, potatoes, rice and others.

And Bayer CropScience went after EPA’s assessment on the ecological impacts of clothianidin, which the agency said poses potential acute and chronic risks for birds and mammals. EPA also said there is “a potential for acute and chronic risk to aquatic invertebrates from foliar, soil and seed treatment uses.”

But Bayer said EPA used a flawed study to come up with a toxicity value that is too low, resulting in an overestimation of the potential hazards to wildlife. “Considering the importance of clothianidin to U.S. agriculture, it is imperative that the EPA use reliable, sound science in their ecological risk assessments,” Bayer said. The neonic is used in seed treatments for corn and sorghum.

On benefits, Bayer said that use of imidacloprid as a seed treatment in mid-South cotton “showed an average yield increase of 102 pounds lint per acre” compared to a fungicide-only base. The company’s Gaucho 600 Floable is used to control insects known as thrips.

EPA had estimated that restrictions on use of neonics in cotton “following pinhead squaring through harvest” could increase costs by $5.70 per acre, or about 2.3 percent of an average cotton grower’s net operating revenue.

Regarding citrus benefits, Bayer said its imidacloprid product, Admire Pro, helps protect from Asian citrus psyllids, in particular by using the “soil drench method” for young trees. The chemical “moves systemically upwards from roots into foliage and prevents psyllids from feeding long enough to transmit the bacteria,” Bayer said in its comments.   

Environmental advocates called for a ban on neonicotinoids, delivering a petition to EPA signed by more than 200,000 people.

“In light of EPA’s own analysis, the agency has a responsibility to protect birds, bees, and aquatic ecosystems from neonicotinoid pesticides,” said Nichelle Harriott, science and regulatory director at Beyond Pesticides. “Failure to do so could potentially have devastating trophic effects on the environment.”

The Center for Biological Diversity, in its comments to the agency, called on EPA to examine impacts to invertebrates other than honey bees, for which the agency released guidance in January 2017.

“Beetles, butterflies, true bugs, crickets and grasshoppers have all been left out of the risk assessment,” CBD said. “Of particular concern is the monarch butterfly, a species that has declined by more than 80 percent in the last two decades and is known to be harmed by neonicotinoid use.”

CBD called on EPA to analyze the effects of mixtures on the environment. “Over 70 products have been approved by the EPA that contain imidacloprid and at least one other active ingredient,” the group said, citing a Purdue University database.