The Silent Trespasser: How Herbicide Drift is Threatening Illinois’ Wild Landscapes

Photos courtesy of the authors.

Year after year, pesticide drift continues to silently injure Illinois prairies and woodlands.

Two years ago, this magazine published our findings from the report Herbicide Drift and Chemical Trespass on Natural Landscapes and Habitats. That report documented the devastating effects of off-target herbicide exposure on Illinois’ plants and trees. Unfortunately, the injuries persist. This chemical trespass continues, leaving scars on the very landscapes that hunters, anglers, birders and outdoor enthusiasts treasure most.

In August of 2024, we released our report “Hidden in Plain Sight – Herbicide drift and chemical trespass. A Summary of 6 Years of Monitoring and Tissue Analysis.” Since 2018, Prairie Rivers Network has been documenting these injuries through its Tree and Plant Health Monitoring Project. Over 6 years, we have logged over 11,500 plant observations across 290 sites in Illinois, ranging from private woodlands to public parks and nature preserves. The results are startling: More than 99 percent of monitored sites exhibit signs of herbicide drift every single year.

Drifting chemicals can include herbicides, insecticides and fungicides. However, those causing visible plant injury, and can be identified without laboratory tests, are herbicides. These herbicides are used primarily in Illinois’ massive row crop industry, but also in chemical lawn and turf treatments.

These chemical intrusions not only degrade the health of our ecosystems but also compromise wildlife habitat, diminish the resilience of our forests, and impair our ability to adapt to a changing climate. It undermines the ecological integrity of Illinois’ most cherished habitats.

Oaks, maples, sycamores and hickories, which provide vital shelter and sustenance for countless species, are among the hardest hit. Prairie wildflowers and woodland understory plants, essential for pollinators and ground-nesting birds, are also showing signs of injury, year after year.

This damage is not confined to rural farm fields or suburban lawns. It reaches deep into protected natural areas, state parks and even private lands managed for conservation. Drifting chemicals are stealing the health and vitality of these places, posing a dire threat to the forests and habitats that sustain Illinois’ iconic wildlife and natural beauty.

An Unseen Epidemic

Widely used herbicides such as 2,4-D, dicamba and atrazine can drift at the time of application, causing harm to nearby vegetation.

However, these chemicals, and many others like them, can also volatilize after application— essentially evaporating into the air — and travel for miles, settling onto woodlands, prairies and even urban backyards. Symptoms of exposure are unmistakable once you know what to look for: cupped or curled leaves, disoriented foliage, yellowing and stunted growth.

As we have observed through our monitoring, for oaks, maples, cherries, hickories and many other species, these signs are more than cosmetic — they’re the harbingers of stress, poor health, and even death.

A Heritage Under Siege: The Story of Beadles Barrens

Among the impacted sites is Beadles Barrens Nature Preserve, a rare prairie-woodland ecosystem in Edwards County. Managed by the Beadles family for four generations, this Illinois Nature Preserve is a living testament to the state’s ecological and historical heritage. The barrens are anything but barren, teeming with prairie wildflowers and oak trees that have stood for generations. Yet today, they’re under extreme stress as a result of repeated herbicide exposures.

Roger Beadles, whose great-great-grandfather purchased the land after the Civil War, has spent his life stewarding the preserve.

“I’ve done everything I can to maintain this post-oak barrens, but seeing herbicide drift slowly killing oaks that have survived 100 to 200 years is devastating,” Roger explained. “There’s no longer acorn production to ensure another generation of trees. You can’t help but wonder if drift is the key factor.”

Recent tissue analyses confirmed his fears. Herbicide exposure at the site is severe, with symptoms observed on 22 plant species from 10 different families.

White oak mortality is accelerating, with an estimated 25 to 33 percent of trees now recently dead. Drift symptoms were found uniformly across the preserve.

What’s at Stake?

The damage herbicide drift inflicts goes far beyond the visible injuries to plants.

Trees suffering repeated exposure show thinning canopies, dieback, and increased susceptibility to pests, disease and extreme weather events. Oaks, in particular, play a keystone role in Illinois ecosystems, supporting wildlife with their acorns, serving as host plants for pollinators, and contributing to carbon sequestration and climate regulation. The decline in health and loss of oaks as a result of repeated exposures, threatens not only biodiversity but also the resilience of entire landscapes.

Moreover, the issue isn’t isolated to rural areas.

Prairie Rivers Network’s research has shown that urban neighborhoods are exposed to both agricultural drift and chemicals from local lawn treatments. The cumulative effect of these exposures is an ecological crisis hidden in plain sight.

A Call to Action

Despite decades of herbicide use, comprehensive systems to consistently monitor drift or its impacts on ecosystems and human health do not exist. Meanwhile, Prairie Rivers Network and other organizations are stepping in, shining a light on this widespread problem in hopes of spurring action. Together with our partners we are educating the public about drift injuries and working to get stronger protections for the wild landscapes we all enjoy and depend on.

The presence of severe exposures often goes unrecognized. It’s easy to misattribute herbicide symptoms to disease or weather, and so many injuries are simply ignored.

But we can’t afford to keep looking away. We need the drift injuries to stop.

For hunters, anglers and anyone who cherishes the outdoors, this issue is deeply personal. Healthy habitats are the foundation of thriving wildlife populations, and losing them to chemical trespass undermines conservation efforts, outdoor recreation, and our shared heritage.

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Kim Erndt-Pitcher is the Director of Ecological Health at Prairie Rivers Network, a statewide conservation organization based in Champaign.

Martin Kemper is a retired Illinois Department of Natural Resources biologist and a volunteer for Prairie Rivers Network who co-leads the monitoring program.