EVANSVILLE, Ind., Oct. 4 (UPI) -- New research has found a widely used and increasingly controversial class of insecticide has "negligible" benefits for commercially grown soybeans. Pesticide makers and farmers disagree.

The class of insecticide, called neonicotinoid, has come under fire in recent years after scientists discovered it might be killing honey bees, monarch butterflies, certain birds and aquatic life.


"We've documented the costs and the downsides of neonicotinoids," said Christian Krupke, an entomology professor at Purdue University, who was one of the 23 researchers who authored a study on the topic.

"So the question we asked with this study was, what are the benefits? Do these insecticides pay off for growers? Do they prevent pest damage? And our findings are that the benefits are negligible."

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The study was an analysis of nearly 200 field studies that evaluated the effects of neonicotinoids on soybean yields across the United States.

The compiled results showed that, on average, neonicotinoid-treated crops produced an average of 2 additional bushels per acre than non-treated crops. When compared to the added cost farmers paid for the insecticide, the payoff is slim, the study concluded.

Contrary opinion

The companies that produce the insecticide and the farmers who use it were quick to refute that verdict.

"The entomologists and agronomists who published this paper might not think that a 2 bushel-per-acre yield increase is a big deal, but clearly growers do," Bayer Crop Science, which sells neonicotinoid-treated soybean seeds, said in an emailed statement.


"And we do, too. The benefits of neonicotinoid seed treatments are well established, which is why thousands of farmers choose to use them every season -- based, like all crop-protection products, on the needs and challenges of their individual fields."

These are farmers like Wayne Fredricks, who grows corn and soybeans in northern Iowa.

"I read through the study," Fredricks said. "It points out that there are certain areas where neonic use is more responsive than others, and we fall right in the middle of one of those areas."

Fredericks -- who employs multiple conservation farming methods, including planting cover crops and not tilling his soil to reduce fertilizer runoff, tested the effect of neonicotinoids on his farm in 2015. He found that the insecticide increased his yields that year by an average of 0.8 bushel per acre.

That 0.8 bushel is an additional $7.20 per acre, if the beans sell at $9 per bushel. (Their price Thursday was $9.11.) The insecticide costs roughly $4 per acre, he said. With 300 acres of soybeans, that means Fredericks earns roughly an additional $1,000 from his harvest by using the insecticide.

"That's an 80 percent return on investment in six months," he said.

Pests a problem

What's more, Fredericks farms in an area that is prone to the kind of seed-eating pests neonicotinoids target, he said. He has lost crops to those pests before.

"We had a case where part of our soybean crop was totally devoured by seed corn maggots and we had to totally replant," he said. "So I know the damage pests can do. That's always in the back of my mind. I know what can happen."


Aside from boosting yield, neonicotinoids are popular among farmers because they provide insurance against such widespread crop loss.

That popularity is broad. Neonicotinoids are the most widely used insecticide in the world, said Scott McArt, an entomology professor at Cornell University, who was not involved in the soybean study.

In the United States, some 40 percent of commercially grown soybeans are treated with neonicotinoids, according to the study. Corn is closer to 100 percent, McArt said.

The substance is a chemically altered version of nicotine.

"The name literally means 'new nicotine,'" McArt said. "The reason nicotine is there in plants is to protect them against insects. The [neonicotinoid] molecule has been synthesized to have a more potent effect on insects. We've altered the compound to be more toxic."

The insecticide first appeared on the market in the mid-1990s and its use grew quickly.

Less toxic

Neonicotinoids are less toxic to vertebrates, like humans, than other kinds of insecticides that were used at the time. Unlike those other insecticides, which had to be sprayed directly onto plant leaves, neonicotinoids are absorbed into the plant through the seeds.

As the plant grows, the substance becomes part of its tissue. That means farmers can buy neonicotinoid-coated seeds instead of spraying their fields with other chemicals.

But the new data on the insecticide's effect on wildlife has many questioning its use.

Multiple studies have shown that neonicotinoids leach off those treated seeds and into the surrounding environment. Once there, they are absorbed into the tissue of wild plants. This makes them a great risk to honey bees, monarch butterflies and other pollinators, according to Cornell University's Pollinator Network.


Other studies have shown the insecticide harms invertebrate aquatic animals and certain types of birds.

The European Union recently banned neonicotinoid use, Canada is considering more restrictions and the U.S. Environmental Protection Agency is conducting a neonicotinoid review that it will release for public comment at the end of this year.

Pesticide producers and scientists warn that placing restrictions on neonicotinoids could result in an increase in the use of other -- more dangerous -- insecticides.

"The assumption that we're going to stop using neonicotinoids and they're not going to be replaced is unrealistic," McArt said. "They will be replaced with other chemical compounds, and those chemical compounds might pose even greater risks. That's something that's not talked about all that much."

Alternates not better

Bayer made a similar point.

"The loss of neonicotinoids would force growers to rely on few older classes of insecticides," the company said.

This argument was one of the key reasons for conducting the meta-analysis of soybean yields, said Krupke, one of the study's authors. Based on the findings, he believes most farmers don't need to be using this kind of insecticide.

"They're sold under the banner that you never know what pests are going to show up, so you'd better treat crops to be on the safe side," Krupke said. "What we showed is the pests just aren't usually there. If they were there, we would be able to see them in untreated seeds. We would have seen them because they would have gobbled them up."


Lacking government intervention, it's up to individual farmers whether they buy neonicotinoid-treated seeds or not.

"If they're in an area that doesn't show an economic response, it may make sense for farmers to not use it," Iowa's Fredericks said.

He added that seed companies are experimenting with ways to reduce chemical leaching by applying it to the seeds with stickier substances.

"I don't disregard the environmental concerns," said Fredericks, who is a member of the National Monarch Collaborative, and sets aside multiple acres of his property for pollinator habitat.

"There is room all around to make improvements. But it should be left up to the individual farmers to make that decision based on what they see in the results from their area."