Neonicotinoid seed treatments under microscope

The U.S. Environmental Protection Agency (EPA) recently released results of a peer-reviewed study on neonicotinoid seed treatments on soybeans.

The agency is seeking public comments on its findings.

The agency’s conclusions were not exactly positive with regard to the use of insecticide seed treatments. In fact, EPA reported that they “provide little or no overall benefits to soybean production in most situations.”

These controversial findings play a role in federal efforts on pollinator health, as neonicotinoids have been identified among the causes of declining bee populations.

Some members of Congress are calling on EPA to restrict use of these pesticides until more is known about their effects on pollinators.

Producers, crop consultants and others can comment on EPA’s assessment by Dec. 22 at!docketDetail;



EPA’s review can be viewed at

UW-Madison soybean specialist Shawn Conley points out that EPA questioning the benefits of neonicotinoids has “generated a significant amount of discussion regarding the use of these insecticides on soybeans.”

Conley urges readers to “spend time, know all the facts on this topic, both environmental and economic, and put forward a well-articulated comment regarding this class of chemistry to EPA.”

Conley and UW co-authors Adam Gaspar and Paul Mitchell published an article in the Journal of Crop Science titled “Economic Risk and Profitability of Soybean Fungicide-Insecticide Seed Treatments at Reduced Seeding Rates.”

They say that use of both insecticide and fungicide seed treatments has dramatically increased during the last decade, due to earlier planting in cooler, wetter soil, which slows emergence and increases exposure to early-season root-rotting pathogens and insects like wireworms and seed corn maggots.

They also mention that at the same time many farmers have increased their seeding rates to insure adequate harvest plant populations even after less than optimal planting conditions.

Soybean seed costs have increased by 58 percent during the past 5 years, according to this UW team.

Furthermore, recent studies point to lower seeding rates as lower final plant populations can potentially achieve similar yields and provide higher return on investment.

Similar yields at reduced seeding rates have been attributed to increased branching and today’s varieties producing more compensatory yield under lower plant populations.

This UW team reports that past research has shown inconsistent results for seed treatments. While growers can read their new results at

It’s noted that CruiserMaxx increased grower profit compared with ApronMaxx and the untreated check (UTC). The component difference between CruiserMaxx and ApronMaxx is the addition of thiamethoxam in CruiserMaxx.

The fungicidal components (mefenoxam and fludioxonil) target Pythium, Phytophthora, Fusarium and Rhizoctonia. The insecticidal component (thiamethoxam) targets insects like bean leaf beetle and seed corn maggot.

The economically optimal seeding rate (EOSR) for ApronMaxx and the UTC are nearly identical for each grain sale price examined by UW researchers, while the CruiserMaxx EOSR was less at several crop prices.

“Based upon our findings, using lower than currently recommended seeding rates may increase grower return, especially at lower grain sale prices and when a fungicide-insecticide seed treatment is used,” the UW researchers say.

The authors of the new Extension research say that “growers should account for their expected grain sale price and seed treatment use when determining their seeding rate and additionally, the components of the seed treatment should be considered.”

“We found that reducing seeding rates when using no seed treatment or a fungicide-only seed treatment (ApronMaxx) may be too risky and provided minimal profit gains.

“In contrast, this study also showed that a fungicide-insecticide seed treatment (CruiserMaxx) reduced economic risk and increased profit across an array of environments, seeding rates (80,000 to 140,000 seeds per acre) and grain sale prices ($9 per bushel and $12 per bushel),” the publication details.

“Furthermore, to realize the lowest risk and highest profit increase with CruiserMaxx, producers should consider lowering their seeding rates to the EOSR according to their expected grain sale price.

“The EOSR for CruiserMaxx ranged from 94,000 to 101,000 seeds per acre and was on average, 16 percent (18,000 seeds per acre) less than ApronMaxx and the UTC across grain sale prices of $9 per bushel and $12 per bushel,” they state.

Returning to EPA’s examination of neonicotinoid seed treatments, Michael Gray, University of Illinois entomologist, points to what he believes are interesting pieces of information cited from EPA’s report.

• On average, from 2008-2012, neonicotinoid-treated seeds were applied on 30 percent of soybean acres (with some individual years approaching 40 percent of soybean acres).

• Across the U.S. (2008-2012), 1,151,000 pounds of imidacloprid and thiamethoxam were used as seed treatments on soybeans.

• Early-season insects were the primary focus and included soybean aphids, bean leaf beetles, cutworms, thrips, and some soil insects (wireworms, seed corn maggots).

• Published data indicate that most usage of neonicotinoid seed treatments does not protect soybean yield any better than doing no pest control.

• In cases where pest pressure does necessitate some type of insect control, efficacious alternatives are available for the key foliar pests of soybeans at a comparable cost per acre.

Gray says EPA makes some assumptions, namely, that nearly all soybean growers are already making foliar pesticide applications of some sort, and that growers would not have to make an additional field pass as “foliar alternative insecticides that target the same pest spectrum as neonicotinoid seed treatments are applied at the same time as a number of current foliar sprays (including herbicides, fungicides, miticides) and can be tank mixed.”

Gray says that some of these assumptions can be challenged. Although use of fungicides is increasingly common, the practice is not routine within every Midwestern soybean field.

Furthermore, Gray states that “the optimum time to apply an herbicide for weed control can vary considerably from that to deter insect damage.”

Gray says that “the use of insecticidal seed treatments within the soybean production system clearly functions as an insurance-based form of pest management and that the long-term trend regarding insect management within large-scale commercial corn and soybean production systems reveals an increasing reliance on product-based inputs (insecticidal seed treatments, Bt hybrids) versus labor and management costs (scouting and use of economic thresholds).”

He also mentions that “it will be interesting to see if EPA does a similar analysis for insecticidal seed treatments in corn.”

ASA adds that the technology partners at Bayer CropScience, Syngenta and Valent USA have unveiled an online educational resource to learn more about the science behind neonicotinoids at

Meantime, the Natural Resources Conservation Service reports honey bees being lost to “diseases, parasites, poor nutrition, pesticide exposure and other issues.”

Last month, U.S. Ag Secretary Tom Vilsack announced Environmental Quality Incentives Program (EQIP) funding for farmers, including those in Wisconsin, to enhance bee food sources and habitat. View story