What Is Imprelis Herbicide? (Conifer Damage Risks)
Imprelis® was a DuPont herbicide containing aminocyclopyrachlor, registered in the United States as EPA No. 352-793. In 2011, the EPA directed DuPont to stop its sale, distribution, and use after reports of tree damage. Suspected exposure can harm susceptible conifers, so stop further disturbance, document symptoms, and seek advice from your state pesticide regulator and a qualified arborist.
A tree beside treated lawn can show damage even when the trunk and surrounding ground look normal. That makes suspected Imprelis exposure hard to judge by sight alone. Needle browning or dying shoots may have more than one cause, and symptoms do not prove which chemical, if any, is responsible.
The safest approach is to treat a credible report of Imprelis use as a site concern, not as a do-it-yourself diagnosis. Do not apply the product, move suspect soil, or rush to replace a tree. First record what is known, then get qualified advice about the site and the affected trees.
Imprelis Identification, Regulatory Status & Site Safety
Imprelis was a DuPont herbicide whose active ingredient was aminocyclopyrachlor. Its U.S. EPA registration number was 352-793. After reports of tree damage, the EPA directed DuPont in 2011 to stop sale, distribution, and use. It is not a current-use recommendation; do not apply it or advise anyone to use it.
The word herbicide means a product made to control unwanted plants. The active ingredient is the chemical in a product that causes its intended effect. In Imprelis, that ingredient was aminocyclopyrachlor. The EPA action followed reports of injury to trees, including susceptible conifers.
A conifer is a cone-bearing tree, such as a spruce, pine, or fir. Reports associated with Imprelis included damage to certain conifers. The specific outcome at a site can depend on the plant, exposure, and other conditions, so a tree’s appearance alone cannot confirm Imprelis injury.
| Question | Practical answer |
|---|---|
| What was Imprelis? | A DuPont herbicide containing aminocyclopyrachlor |
| What was its EPA registration number? | 352-793 |
| What did the EPA direct in 2011? | DuPont to stop sale, distribution, and use |
| Can a suspected site be judged safe by looking at it? | No. Soil residues may not be visible |
| Should you apply it or recommend using it? | No |
If you have a container, label, invoice, or treatment record, keep it. The product name and registration number can help regulators and an arborist assess what may have been used. Do not handle or dispose of a container in a way that conflicts with its label or local instructions.
Key next step: If Imprelis use is possible, stop any suspected application and begin documenting the site before moving soil, plants, or yard waste.
Conifer Injury Assessment and Immediate Field Response
Imprelis-related injury reports included needle browning, shoot or branch dieback, and abnormal or distorted new growth in susceptible trees. These signs can also have other causes, so use them to flag a concern, not to make a diagnosis. Record where symptoms appear and when they began.
Dieback means that a shoot or branch is dying back from its tip or along its length. Distorted growth means new growth appears misshapen or develops abnormally. Note whether symptoms affect one tree or several, and whether affected trees sit near treated turf or another area where herbicide may have been applied.
Take these steps if exposure is suspected:
- Stop any further suspected application.
- Photograph the whole tree and close views of needles, shoots, and branches. Include the date.
- Mark affected trees in a way that does not damage them.
- Write down the product name, application date, rate if known, weather, and boundaries of the treated area.
- Keep people, pets, and equipment out of affected areas as appropriate.
- Do not move suspect soil, clippings, or mulch to untreated areas.
Avoid cutting, digging, or treating a tree based only on a symptom photo or online description. A qualified arborist can assess the tree’s condition and whether it presents a safety concern. If a tree appears unstable or has large dead limbs over places people use, keep clear and ask an arborist to assess it promptly.
A declining conifer beside treated lawn deserves particular attention. Exposure may involve treated soil or roots, and the visible tree may not show the full extent of the affected area. Removing the tree or replacing soil without first assessing the treatment area can leave a possible source in place or spread suspect material.
| What you observe | What to do next |
|---|---|
| Brown needles or dying shoots | Photograph and record the pattern; ask an arborist to assess it |
| New growth looks distorted | Record when it appeared and which parts of the tree are affected |
| A tree is near a suspected treated area | Map the distance and treated boundaries; do not assume exposure is confirmed |
| Several trees show changes | Document each tree separately and share the pattern with the assessor |
| A tree or limb may be unsafe | Keep people away and contact a qualified arborist |
Key next step: Preserve the pattern of evidence. Photos, dates, and a simple site map can help distinguish a focused concern from a general yard problem.
Documentation, Reporting & Qualified Arborist Evaluation
A useful report combines the product information, application history, site layout, and symptom timeline. Contact your state pesticide regulatory agency and a qualified arborist. The regulator can advise about reporting and site-specific restrictions; the arborist can assess tree condition and hazards. Neither a photo nor a symptom list alone confirms the cause.
Before contacting them, gather:
- Any product label, container information, invoice, or contractor record
- The application date and rate, if known
- The weather around the application, if recorded
- A map showing treated boundaries, trees, and nearby areas
- Dated photos and notes about when each symptom began
- Details of any soil, clippings, or mulch that may have been moved
Keep statements clear about what you know and what you are unsure of. For example, say that a lawn was reportedly treated, but the product or date is unknown, rather than presenting a guess as fact. Ask the state regulator whether the situation should be reported and whether rules apply to the site or its materials.
Illustrative field scenario: A homeowner notices browning on a spruce beside a lawn and finds an old lawn-treatment record. The record names a product but does not show the application boundary. The useful next step is to share the record, photos, and a sketch of the yard with the regulator and arborist, rather than assuming the spruce was exposed.
This is an example of a response process, not a documented individual case or proof that Imprelis caused damage. Similar-looking symptoms can arise for different reasons. Qualified assessment helps prevent a suspected cause from being treated as certain before the site history and tree condition are reviewed.
Key next step: Ask the regulator about reporting and restrictions, and ask the arborist to evaluate the affected trees and any safety risks.
Soil, Planting and Site Management After Suspected Exposure
A site may need assessment even if its surface looks normal. Residues in treated soil can injure susceptible plants, so elapsed time and a clean-looking lawn do not establish that replanting is safe. Do not move suspect soil or plant a susceptible tree there until qualified authorities provide site-specific guidance.
Do not spread soil, grass clippings, or mulch from a suspected area into untreated parts of the yard. Moving material can expand the area of concern. Avoid unverified fixes such as soil removal or dilution: excavation may disturb roots, and moving material may spread residues. Do not try chemical treatments unless a qualified authority gives site-specific instructions.
| Proposed action | Why caution matters | Safer next step |
|---|---|---|
| Plant a replacement conifer | Soil residues may still pose a risk to susceptible plants | Ask the regulator and arborist for site-specific guidance first |
| Move soil or mulch elsewhere | It may transfer suspect material to another area | Keep it in place until you receive disposal or handling instructions |
| Remove or dilute soil | It can disturb roots or spread material | Do not proceed without qualified direction |
| Remove a visibly damaged tree | It may not address a possible source in the treated area | Have an arborist assess the tree and site |
| Wait a set period, then replant | Time alone does not prove the soil is safe | Seek an assessment rather than relying on a calendar |
If a tree must be removed for safety, ask the arborist and regulator how to handle material from the site. Follow applicable disposal and regulatory instructions. Do not assume that removing the tree also removes any soil concern.
Key next step: Leave soil and plant material where they are until you know what handling and planting guidance applies to that specific site.
Conclusion and FAQ
When Imprelis exposure is possible, the main priorities are to stop further disturbance, document the site, and get qualified advice. The product contained aminocyclopyrachlor, and the EPA directed DuPont to stop its sale, distribution, and use in 2011 after reports of tree damage. Symptoms can raise concern but do not confirm the cause.
What should I do first if I suspect Imprelis was used?
Stop any suspected application, photograph symptoms, record site details, and contact your state pesticide regulator and a qualified arborist.
What was the active ingredient in Imprelis?
The active ingredient was aminocyclopyrachlor.
What was Imprelis’s U.S. EPA registration number?
Its registration number was 352-793.
Is Imprelis still a product I should use?
No. In 2011, the EPA directed DuPont to stop its sale, distribution, and use after reports of tree damage. Do not apply or recommend it.
What symptoms were reported on conifers?
Reports included needle browning, shoot or branch dieback, and abnormal or distorted new growth. These symptoms do not, by themselves, prove Imprelis exposure.
Can I tell from the tree’s appearance whether Imprelis caused the damage?
No. Similar symptoms can have other causes. An arborist can assess the tree, while regulators can advise about reporting and site concerns.
Can soil still be a concern if the lawn looks normal?
Yes. Residues in treated soil may injure susceptible plants, and surface appearance alone cannot establish that the site is safe.
Should I replace the soil or mix it with clean soil?
Do not do so without site-specific guidance. Moving or disturbing soil may spread suspect material or harm roots.
Can I replant a conifer after waiting a certain amount of time?
There is no safe interval to assume from elapsed time alone. Ask the state regulator and a qualified arborist for site-specific guidance before replanting.
What should I give the arborist or regulator?
Share product or label information, application records, dates, weather if known, a site map, and dated photos showing symptoms and their locations.
(This article was written by one of our staff writers, Evan Bradley. Visit our Meet the Team page.)
