1. Imprelis® Damage to Trees Primer
Imprelis has become a new concern for tree health in Minnesota. This brief primer is intended to outline how the chemical harms plants, the symptoms of damage, the range of host plants, proposed treatments or therapeutic measures, and any course of action that tree owners have for tree loss compensation.

2. What is Imprelis®? A Broadleaf Herbicide for Turf and Right-of-way Use
Introduced by DuPont in Spring, 2011
Active Ingredient: aminocyclopyrachlor
In spring 2011, a new DuPont herbicide with the active ingredient aminocyclopyrachlor was sold with the trade name Imprelis and used to control weeds on many turf areas (lawns, golf courses, sports fields, rights-of-way etc.)

3. Why Imprelis® Turf Magazine - November, 2010
TURF SCIENCE
New Products
“Control Weeds Even on Rainy Days
DuPont Imprelis herbicide...control dandelion, clover and plantains, as well as tough broadleaf weeds...even during reseeding or rainy days...a low application rate... and is the first compound in an advanced generation of herbicides.”
This herbicide was touted to be “the first compound in an advanced generation of herbicides” that could be applied even in the rain and effectively control a wide range of broad-leaved turf weeds. 3

4. How does Imprelis® Work?
Turf Magazine - November, 2010
TURF SCIENCE
New Products
“Imprelis® is readily absorbed by plant leaves and roots, stopping the growth of target weeds by interfering with the hormonal balance necessary for normal shoot and root development.”
The mode of action for this herbicide is essentially as a growth regulator. 4

5. Imprelis® related to Clopyralid
Clopyralid introduced as a broadleaf herbicide.
Clopyralid found in organics waste stream.
Decomposition processes in compost...did not degrade the molecule.
Compost was herbicidal.
The sole active ingredient of Imprelis® is similar to another broad-leaved turf herbicide that was introduced over a decade ago and also caused landscape and environmental issues.
Clopyralid is an herbicide commonly used in farming and forestry applications. Trade names are Stinger and Transline. Clopryladid is persistent and moves with water. Clopyralid is a highly selective herbicide affecting composites. This is different from aminocyclopyrachlor 5

6. Imprelis® Long residual -- not biodegradable
High concentrations remain in plants
Herbicidal at very low concentrations
Recycled in grass clippings and tree leaves
Evergreen & deciduous plants affected
Also, similar to the characteristics of clopyralid, Imprelis® tends to be very effective at low application rates or concentrations in the soil, doesn’t readily break down and recycles in the landscapes’ organic tissues that have taken up the chemical. 6

7. What Did DuPont Do? Introduced by DuPont in Spring, 2011
By June, 2011, damage to trees and shrubs was reported...
By end of summer 2011, Imprelis® was pulled from use
In effect, Imprelis® was used for less than one growing season in Minnesota. Despite that fact, the damage it has caused has continued for over two growing seasons to date. 7

8. What plants are affected?
All woody trees, shrubs, vines
Damages new growth
Spruce, honey locust, cottonwood are especially sensitive
As more plants are diagnosed with the damage, there’s no reason to believe that any woody plant is immune to the effects of Imprelis®. 8

9. Symptoms of Imprelis® Damage
Dead buds, shoots, pine candles
Twisted, fused needles
Contorted, chlorotic leaves
Tumorous growths on twigs, stems
Twisted, “stretched” twig growth
Death
Symptoms of Imprelis® damage are continually emerging. Symptoms range from typical growth regulator damage: contorted growth, stunted growth, flattened/fused growth; to dieback and death. 9

10. Symptoms of Imprelis® Damage
Common symptomology with spruce includes dieback, tumorous galls forming just below terminal buds and stem swelling below dieback areas on twigs.
Colorado Spruce dieback, galls, stem swelling 10

11. Symptoms of Imprelis® Damage
In addition to the dieback and gall growths, fused needles are commonly symptomatic on Colorado spruce. One of the concerns is how will these trees look in 2-3 years when that needle growth is dropped?
Colorado Spruce fused needles 11

12. Symptoms of Imprelis® Damage
Needles and twig death was one of the first symptoms noticed on spruce trees in the summer of Most of these trees did not recover.
Black Hills Spruce 12

13. Symptoms of Imprelis® Damage
Twisted growth
Norway spruce seems to be particularly susceptible to Imprelis® damage and dies very quickly. Those that do survive often have the twisted twig growth as seen in the picture to the right. This contorted growth is very common with growth regulator damage.
Norway Spruce - death 13

14. Symptoms of Imprelis® Damage
White pine, too, appears to be very susceptible to damage, often dying within a year.
White Pine: 2011 on the left, 2012 on the right 14

15. Symptoms of Imprelis® Damage
Needle death, swollen twigs, galls, distorted needles
An assortment of damage symptoms to white pine including needle death, swollen twig growth, tumorous galls and distorted needles.
White Pine 15

16. Symptoms of Imprelis® Damage
Damage to Northern white cedar has been common and includes needle and twig death, stunted terminal growth and tumorous galls on twigs.
Northern White Cedar needle & twig death stunted growth, galls 16

17. Symptoms of Imprelis® Damage
Damage to honeylocust has been particularly damaging, distorting and ubiquitous. Symptoms range from leaf distortions similar to plant bug infestation to leaf and twig dieback.
Leaf distortion, dieback, similar to plant bug infestation
Honeylocust 17

18. Symptoms of Imprelis® Damage
In addition to dieback and severe thinning of the foliage on honeylocust, Imprelis® causes extensive gall formation on the petioles, twigs, branches and stems. The long-term effects of these galls is unknown at this time.
Honeylocust Galls on twigs, branches and stems 18

19. Symptoms of Imprelis® Damage
Symptoms of Imprelis® damage on Ginkgo to date has been confined to leaf margin scorch and/or chlorosis and distorted new, terminal growth.
Ginkgo 19

20. Symptoms of Imprelis® Damage
Freeman Maple
Distorted terminal growth
Damage symptoms on maples have ranged from leaf wilting to this unique distortion of terminal growth on freeman maples. Again, the long-term effects of this damage is unknown. 20

21. Symptoms of Imprelis® Damage
Damage symptoms on cottonwood and other species of poplars has included leaf distortion, tip dieback and complete death on big-toothed aspen.
Cottonwood Leaf distortion
Tip dieback
Death of big toothed aspen 21

22. Mitigation Measures Prune and remove damaged growth
Chemical moves with water
. . . water moves down-hill
Damage seems to be confined to new growth, so removing new growth gets the chemical out of the plant system. Make sure to destroy those pruned branches, though, rather than chipping them or composting them.
The chemical moves with water and if the water moves down hill, plants at the bottom will be effected. Avoid planting any new plants down hill from a known use area until all symptoms have subsided. 22

23. Mitigation Measures Remove all contaminated materials
Including grass clippings, leaves, wood and other plant debris until at least 2014
Burn or landfill affected yard waste
For replacement plantings
Remove and replace contaminated soil
Amend edges of excavation site with activated carbon
Since there is so little known about the longevity of the chemical and the damage from it, remove all plant materials that could have the chemical in them at least through MPCA has issued a waiver through 2013 for lawn/wood waste going to landfills.
If an area is going to be replanted, replace as much soil as possible with untreated soil. This is not real practical due to costs involved if it’s on a large scale.
Activated carbon can tie up the chemical, but it’s very expensive and at some point, the chemical will again be released. So this, too, is not an optimal treatment. 23

24. Compensation for Tree Loss?
Carefully document all damage:
Maintenance records
Dates
Photos
Symtomology
DuPont claim site:
Only through 2013
DuPont does have a web site with a claims/compensation section. Consult this before removing any plants from the landscape. Document all damage carefully and do not settle any claims until you are certain all plants are returning to health.
Claims with DuPont are currently only taken through the end of MDA can advocate for a longer period if damage continues to increase or worsen. 24

25. For More Information
Imprelis® Update: 2012 Field Notes on Injury and Recovery.
A Turf Professional’s Guide to Suspected Imprelis® Herbicide Injury in the Landscape.
MDA:
Purdue University’s web site from their Plant and Pest Diagnostic Laboratory is currently one of the best reference sites.
The MDA’s website has a fact sheet, call if suspicions about Imprelis damage arise. 25

26. Questions All Imprelis® symptoms images were generously shared by
Acknowledgement page.
All Imprelis® symptoms images were generously shared by
Manuel Jordan: Heritage Shade Tree Consultants and
John Lloyd: Plant Health Doctors.com 26