The U.S. EPA recently re-opened the public comment period on the draft ecological risk assessments for several pesticides, including all pyrethroid insecticides. The comment deadline is July 7. EPA re-opened the comment period in response to extension requests received from various stakeholders, and Iowa farmers are urged to participate.
Every 15 years, EPA reassesses all pesticides, ensuring that crop protection compounds continue to meet the standards established under the Federal Insecticide, Fungicide and Rodenticide Act. EPA is required to use the latest science to evaluate the environmental impacts of these products in this process. However, in its latest review for pyrethroid insecticides, EPA is relying on insufficient science, according to many registrants. Crop protection industry groups and other key stakeholders provided EPA with volumes of additional information, data and risk refinements, but so far, EPA hasn’t fully considered these important contributions in their risk assessments.
Pyrethroids are synthetic chemical insecticides, a botanical form derived from chrysanthemum flowers, considered to be safer than older chemistries. Both forms work by altering nerve function and causing paralysis in target insect pests in crop, horticultural and home uses. Three pyrethroids (bifenthrin, cyfluthrin and tebupirimphos) were used on 10 percent of the corn acres in Iowa and 12 percent of U.S. corn acreage in 2016, according to a National Ag Statistics Survey ag chemical survey. Bifenthrin, chlorpyrifos and lambda-cyhalothrin were used on 25 percent of Iowa soybeans and 22 percent of U.S. soybeans in 2015. The advent of biotechnology has generally reduced pyrethroid use, particularly in corn, and so its annual use is highly variable.
Yet, these products are essential tools for integrated pest management in Iowa crops. When used in rotation with other chemistries as part of an integrated pest management program, they help biotech traits.
Soybean Aphid Treatment
Soybean aphids were first spotted more than 16 years ago. They’ve caused problems somewhere every year since, although damage is hard to predict; aphids don’t do well if it’s too hot, cool, too wet or dry. But aphid populations can explode when conditions are ideal, doubling in less than two days. That means the tiny pests can go from below-threshold numbers to yield-damaging levels in less than a week if they’re not treated.
As it stands, the EPA’s latest risk assessment could limit or prohibit use of some of the most effective pyrethroid treatments available. It suggests that use could be limited or prohibited by wind speed, for example, or large buffer zones may be required, relegating some affected fields to significant yield damage, as much as 5 to 10 bushels per acre when they exceed economic thresholds.
EPA’s incomplete risk assessments for pyrethroids raise concerns for some aquatic organisms in some areas and non-ag uses. But EPA’s overly simplistic risk assessment methods don’t fully consider the actual chemical characteristics of these products. Using the bifenthrin example, again, this active ingredient is hydrophobic, meaning it repels water. It biodegrades in sunlight and binds tightly to soil particles, further limiting its availability to non-target aquatic organisms in their natural environments. EPA’s laboratory studies don’t take these qualities into consideration, many crop scientists say, thereby exaggerating its environmental impact.
Farmers Urged to Comment
To prevent losing access to this important pest management tool, Iowa farmers are urged to tell EPA how these products fit into their cropping programs. Tell EPA how pyrethroids are part of your integrated pest management and resistance management “tool box,” including use of resistant varieties, early planting dates, scouting, proper sprayer pressures and nozzles, use of alternate the modes of action, and understanding the stages of a crop’s development cycle when a product is the most effective.
Tell EPA how you use precision agriculture systems to maximize the efficiency of your crop inputs, how you plant seeds with biotech traits to increase yields and decrease the need for crop protection compounds. Give examples of how you work every day to conserve soil, water and other natural resources using the latest techniques. Gives estimates of the cost if these products are limited or prohibited. Remind EPA that sound science should be just as important to them in its risk assessment process as it is to you in your daily farm management.
How to Comment
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