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Healthy Forests, Today and Tomorrow

The Illinois Forestry Association (IFA) is sharing this information in an effort to bring awareness to a serious threat to our trees and forests. 

"Herbicides can be effective tools for controlling unwanted weeds in the landscape". (Nebraska Forest Service)  However, in recent years, IFA members have seen an alarming increase in unintended damage to trees and other landscape plants in multiple counties throughout our state from off-target herbicide exposure. 

Testing and analysis by Illinois Department of Agriculture (IDOA) and Illinois Department of Natural Resources (IDNR) representatives have confirmed the presence of chemicals including 2,4-D and dicamba in damaged foliage samples in multiple cases.  This foliage damage appears to have contributed to a decline in health and increased mortality of many of our tree and plant species including, but not limited to oaks, elms, maples, redbud, honeylocust, hickories, flowering dogwood, and sycamores.  

About Trees

 Trees are essential to our ecosystem and as a renewable resource provide social, communal, environmental and economic benefits.  We as humans could not survive without the process of photosynthesis during which trees convert carbon dioxide to oxygen.  Photosynthesis  is also essential in the life cycle of deciduous trees whereby leaves collect sunlight and turn it into nutrients that the tree uses for energy.  It is safe to say that the health of a tree is directly dependent on the health of its foliage.

What Are the Primary Symptoms of Herbicide Exposure?

  • "Leaves that are cupped, curled, twisted, deformed, puckered or strapped (narrowly elongated)". (Nebraska Forest Service)
  • "Clusters of stunted shoots or abnormally elongated and twisted shoots". (Nebraska Forest Service)
  • A thinning canopy (loss of foliage).

Why is the Damage Occurring Now?

In recent years with the emergence of weeds resistant to the glyphosate herbicides, applicators have significantly increased utilization of other chemicals including 2,4-D and dicamba for pre-emergent and post-emergent weed control.  Many formulations of dicamba and 2,4-D (including the “low volatile” ester formulations) are prone to volatilization and drifting.  Multiple factors affect volatilization, but higher temperature and lower humidity tend to favor increased volatilization.  Unfortunately, under certain atmospheric conditions these chemicals can vaporize and drift considerable distances for several days after application.  These chemicals are toxic to many tree species and  can cause severe disfigurement of the leaves, which compromises photosynthesis.  Toxicity combined with compromised photosynthesis can lead to reduced flowering, fruiting, nut production and growth, increased risk of disease and insect damage, and causes decline and even subsequent premature death of trees.   

What is Being Done?

The Illinois Department of Natural Resources began studying and monitoring tree damage in 2018 and continues to gather facts and evidence to help resolve the problem.  In the meantime, the IFA believes that through awareness and education additional damage to our forested lands and trees can be mitigated.  

How Can Applicators Help Prevent Damage to Trees?

  •  "Read and follow all regulations and herbicide label directions, particularly restrictions that help limit drift, vaporization, and runoff. Look for precautionary statements regarding trees". (Nebraska Forest Service)
  • Be particularly careful with chemicals capable of volatilizing and drifting.  Please note that in several cases involving herbicide damage, applicators were unaware of the damage that was caused by volatilizing chemicals due to the distance at which the damage occurred relative to the target application site (e.g., >1/3 mile). 
  • Fortunately, there are effective alternative chemicals for weed control that are not prone to off-target damage.  Chemical providers and agronomists can help determine suitable products for your needs.  
  •  "Be aware of surrounding properties with sensitive vegetation including parks, gardens, windbreaks, landscape nurseries, orchards, vineyards, organic farms, native woodlands and other natural areas. Visit for locations of growing operations near you". (Nebraska Forest Service) Careful consideration should also be given to residential areas. 
  •  "Most damage occurs in spring when trees and other plants are leafing out with susceptible new growth.  If practical, shift weed control to autumn when many weeds are more easily controlled and damage to trees is reduced". (Nebraska Forest Service) 
  • "When possible use alternate methods of weed control such as cultivation, mulching, use of cover crops, and mowing weedy tree sprouts". (Nebraska Forest Service)  

    How Can Landowners and Concerned Citizens Help?

If you see something, say something.  Pay particular attention to trees for foliage damage symptoms between mid-March through late May when they are developing leaves and are particularly vulnerable to herbicides.  Once these symptoms develop, they are typically observable for the remainder of the growing season on
damaged trees. Please reference for a detailed photo library of herbicide symptoms on a variety of tree species.  

"Damage from weather, insects, and diseases can be confused with herbicide damage". (Nebraska Forest Service) If you have trees exhibiting foliage damage, and want help in diagnosing the injury, please contact your county extension office or local IDNR forester › dnr › conservation › Forestry.  Contacting IDNR may not always result in a site visit.  However, district foresters are likely to provide a form that can be filled out and returned.  District foresters will keep track of these forms and attempt to see some affected sites as time permits. 

If you believe your property has been damaged by pesticide misuse, call the IDOA’s Bureau of Environmental Programs at 1-800-641-3934 (voice and TDD) or 217-785-2427 for a complaint form or visit their website at

Individuals with specialty crops or timber property are encouraged to register with Fieldwatch to alert applicators of their sensitive crops.  FieldWatch is a non-profit company with a Google Maps based registry built to enhance communications that promote awareness and stewardship activities between producers of specialty crops, bee keepers and pesticide applicators.  Their mapping tools are FREE for use, and all areas mapped in their registries have oversight by each given state / province or area in which they are mapped.

Thinning Canopy

Twisted, Curled Leaves

Cupped Leaves

Cupped Leaves

Stunted Leaf Growth/Cupping

Foliage Damage

               Help The IFA Monitor

With your help, we believe that we can help in mitigating this issue by collecting reports from Illinois landowners who are suspicious of off-target herbicide damage occurring on their lands. With the data we collect from you, we hope to capture the frequency and magnitude at which off-target herbicide damage is occurring in Illinois. We will share this information with other forestry organizations and agencies so that we can have a better collective understanding of the issue. Access this report form by clicking the blue button below labeled "Herbicide Damage Report Form".

Before Submitting Report Form Remember

Pay close attention to the symptom photos above. Multiple factors can lead to tree decline and mortality. Having multiple species of trees showing similar symptoms can be a helpful indicator of off-target herbicide injury. This report form is not an official complaint. The IFA cannot confirm with absolute certainty that your tree damage is herbicide drift related. However, through your reporting, we can collect data that is highly suspect of herbicide injury.

Literature Cited: Nebraska Forest Service - Herbicide Damage to Trees

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