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Farmers are using too much pesticide-coated seed, which has been found to be harming nature

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Spring planting season for crops begins in southern states and moves north. As farmers plant their seeds, they spray huge amounts of pesticides into the air without using any at all.

Almost every field corn seed planted this year in the United States will be coated with neonicotinoids, the most widely used class of insecticides in the world. So will seeds for about half of U.S. soybeans and nearly all cotton, along with other crops. By my estimate, based on acres planted in 2021, neonicotinoids will be deployed across at least 150 million acres of cropland – an area about the size of Texas.

Insecticide neonicotinoid compounds are extremely powerful pesticides, killing pests at concentrations that are usually just a few parts per million (ppm). They’re considered to be relatively safe for humans compared to older pesticide chemicals, but they may pose some risks to birds and fish.

Over the last ten years, scientists and conservationists have pointed out that neonics are harming bees. They’ve also claimed that these pesticides harm other wildlife, too, such as birds that eat the coated seed.

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To address these concerns, several states have passed laws restricting the use of neonicotinoids. Others are considering similar legislation. Advocacy groups are also challenging the EPA’s failure to act.

As an applied entomologist and extension specialist working with agricultural producers on pest management, I believe that American farm operators use pesticides far too often, with mounting harm to natural ecosystems. Furthermore, our ongoing studies indicate that encouraging beneficial predators on farms can greatly diminish pesticide usage.

Insecticides on seeds

Most neonicotinoid pesticides in the United States are applied directly onto crop plants as a coating. These include products such as Bayer’s Thiamethoxam (Actara®) and Syngenta’s Imidacloprid (Admire®).

While these chemicals can help control certain types of insects that attack agricultural fields, they do not target the primary pest species that cause significant losses to agriculture.

In addition, these pesticides are often sprayed onto food sources, including fruits and vegetables, and then eaten by people. Therefore, consumers may unknowingly consume pesticide residues through contaminated produce.

Since 2004, the percentage of acres planted with neonicotinoids has been increasing steadily. However, from 2011 to 2014, the number of acres treated with neonicotinoids nearly doubled. Unfortunately, in 2016, the federal agency responsible for monitoring pesticide use stopped collecting data used to estimate this increase.

Unlike most pesticides, neonicotinoid insecticides are water soluble. When a plant grows from a neonicotinoid-coated seeds, its roots can absorb part of the insecticidal coating. This can protect the plant for a limited period of times from certain pests.

However, only a small portion of the insecticide applied onto seeds actually gets into seedlings; for instance, corn seedlings absorb only about 2%. The most important issue: where does the rest of the insecticide persist?

Soybean seeds treated with neonicotinoids (dyed blue to alert users to the presence of pesticide) and treated corn seeds (dyed red) versus untreated seeds. Ian Grettenberger/PennState University, CC BY-ND

Pervading the environment

One answer is that leftover insecticide not taken up by plants can easily wash into nearby waterways. Neonicotinoids from seed coatings are now polluting streams and rivers across the U.S.

Studies have shown that neonics are harming and killing aquatic insects that are vital sources of nutrition for fish, birds, and other animals. Recent studies have linked their widespread usage with declines in bird populations and a commercial fishing industry in Japan.

We’ve shown that neonicotinoid pesticides can poison insect predators in crop field, and subsequently, we’ve shown that they can reduce their population by up to 20%.

We recently discovered that many pesticides can kill bees and other beneficial pollinators. These include neonicotinoid insecticides which are widely used in agriculture.

Slugs, shown here on a soybean plant, are unaffected by neonicotinoids but can transmit the insecticides to beetles that are important slug predators. Nick Sloff/Penn State University, CC BY-ND

Are neonicotinoids essential?

Neonicotinoid proponents claim that neonicotinoids are essential for controlling pests and therefore offer significant benefits to growers.

But they usually compare neonicotinoid seeds with the costs of conventional pesticides, which are assumed to be necessary on every acre of crops. Their claims rely on assumptions about the need for pesticide use on every acre of crops, so their arguments don’t stand up to scrutiny.

Field studies suggest that neonicotinoid seed coatings may not offer significant benefits because their effects on pests tends to be minimal.

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Should the United States ban neonicotinoid pesticides or adopt stricter limits than those imposed by New Jersey?

As I see it there are two main issues with neonicotinoid pesticides. First, they are not effective against some pests (e.g., aphids).

Second, they may be harming beneficial insects (e.g., bees) and pollinators. Therefore, I think we need to limit their uses for field crop seeds.

Instead, I think agricultural firms should focus on promoting IPM (integrated Pesticide Mgmt) instead of relying on chemical pesticides. And farmers should adopt IPM practices rather than rely on chemicals.

As concerns mount about neonicotinoid pesticides, agricultural companies have done little to change their practices, and farmers often have very limited choices if they don’t wish to use coated seeds. Farmers often face pressure from seed suppliers to buy coated seeds.

Insects are declining worldwide at an alarming rate, and scientists are warning that neonicotinoids—a class of pesticides used widely throughout the world—are playing a role in the decline. I think it’s time for us to start considering regulatory options to curb the use of these harmful chemicals.