Corn and soybean seeds colored red and blue, respectively, have become an all-too-common sight on U.S. farms. The seeds are given a colorful hue because they’ve been treated with neonicotinoid pesticides, and the coloring is one of the only ways to tell them apart from their untreated, yellow counterparts. In 2018, nearly every field corn seed sown in the U.S. contained the insecticides, along with about half of soybeans and most of the cotton.1
(For clarification, there are three kinds of corn: field, sweet and popcorn. Popcorn is never genetically modified, 2 although some brands may include GMO Ingredients, for example, if you purchase preflavored bags. Sweet corn is that tasty corn you eat right on the cob every summer, and it’s moist when it’s harvested,3 unlike field corn, which is left on the stalk longer so it can dry out in preparation for processing. Field corn is then used to make processed food products and animal feed.)
According to John Tooker, associate professor of entomology at Pennsylvania State University, “ … [T]hese insecticides will be used across at least 150 million acres of (field corn) cropland, an area about the size of Texas.”4
While some attention has been given to neonicotinoids’ potential role in bee decline, Tooker believes the chemicals are having an even greater pernicious influence on insects, such that entire ecosystems could be in jeopardy. What’s more, neonicotinoids are only one type of agricultural chemical that’s being used in excess while the environmental consequences begin to unfold all-around us.
Neonicotinoids Devastating the Environment While Reducing Farmers’ Crop Yields
In recent years, the acreage of crops treated with neonicotinoids has skyrocketed, as has the volume used. From 2011 to 2014, Tooker says, seed suppliers doubled the amount of insecticide applied to each seed. During that time, the number of pests have stayed largely the same, as they have since the 1990s, when only 35 percent of U.S. corn acres and 5 percent of soybean acres were treated with neonicotinoids.
Even at those levels, “pest populations did not cause economically significant harm very often,” according to Tooker. “This suggests that it is not necessary to treat hundreds of millions of acres of crops with neonicotinoid seed coatings.” Further, while the chemicals are very effective at killing insects, this is part of the problem.
Not every insect is a pest; in fact, many are beneficial. Research by Tooker and colleagues found that planting neonicotinoid seeds kills off insects that prey on slugs — prominent corn and soybean pests — thereby reducing crop yields.5
Other research revealed that planting seeds coated with neonicotinoids reduced predatory insects by up to 20 percent.6 Such insects help to reduce pest infestations on crops from insect pests like black cutworm, giving another example of how using neonicotinoids may actually lead to reduced crop yields for farmers. There are other alarming effects as well, particularly since only about 2 percent of the chemical is taken up by the plants.
“The critical question is where the rest goes,” Tooker says, and it’s known that some of it ends up in nearby waterways where the chemicals are now polluting rivers and streams and killing off aquatic insects that other species depend on for food. Not only can the treated seeds directly kill birds if they pick one up for a snack, but research suggests that declines in insect-eating birds are associated with high usage of neonicotinoids.7
An investigation by the U.S. Environmental Protection Agency (EPA) even found that treating soybean seeds with neonicotinoids provides no significant financial or agricultural benefits for farmers.8 The researchers also noted there are several other foliar insecticides available that can combat pests as effectively as neonicotinoid seed treatments, with fewer risks.
Duration of Pesticide Exposure Is a Ticking Time Bomb
Risk assessments for pesticide application often consider only the present time of use and don’t factor in that usage may increase over time or the modes of application may change. In reality, pesticide usage is changing rapidly and non-target species are being exposed to multiple chemical agents for long durations of time, with unknown consequences. Writing in the journal Frontiers in Environmental Science, researchers tackled the question of how changing pesticide usage over time may affect migrating amphibians such as frogs.9
They looked in particular at glyphosate, the active ingredient in Monsanto’s Roundup herbicide, which has been continuously increasing since it was introduced in the 1970s. “Glyphosate-based herbicides can be used as an appropriate indicator for assessing how changes in pesticide application modes affect wild-living organisms in agricultural landscapes over time,” they reasoned, estimating that the use of glyphosate in German agriculture increased by 5.7-fold from 1992 to 2012.
During this time, amphibians also became more likely to transverse fields treated with the chemical during their travels. Their analysis found that juvenile great crested newts and fire-bellied toads faced the highest likelihood of coming into contact with the herbicides, while moor frogs and spadefoot toads were subjected to moderate increased of exposure ranging up to 3.6-fold higher.
Such exposure could be devastating, as glyphosate-based herbicides are toxic to amphibians, especially during the aquatic life stages, with POEA (polyethoxylated tallow amine), a surfactant commonly added to the chemical formulations, thought to be responsible for many of the adverse effects. Although POEA-free glyphosate-based herbicides were introduced in Germany in 2013, there is still concern that glyphosate-based herbicides could lead to problems with development, malformations, stress and death in amphibians.10