The Purdue Plant and Pest Diagnostic Laboratory

Growth Regulator-Type Herbicide
Symptoms on Spruce and Pine

Tom Creswell, Lab Director
Gail Ruhl, Plant Disease Diagnostician
Aaron Patton, Turfgrass Extension Specialist
Steve Weller, Extension Weed Scientist

The PPDL has received samples of Norway spruce, white pine, dawn redwood and several other woody ornamental species that exhibit symptoms similar to those that can be caused by synthetic auxin (growth regulator type) herbicides. Typical symptoms caused by these herbicides can include epinasty (twisting and curling) of needles, shoots and tips of branches. New growth may turn brown and die. On broadleaf plants, leaf cupping (upward or downward) may occur and in extreme cases, new leaves may appear irregular in size and shape (usually smaller than normal) and have abnormal leaf margins. Samples submitted to the PPDL as well as reports of injury in other areas of the country appear to be linked back to the common denominator of the herbicide aminocyclopyrachlor applied to surrounding lawns for broadleaf weed control. The damage appears to be from root uptake rather than from drift or volatilization. Herbicides with good soil activity may cause problems on nearby broadleaf ornamentals through root uptake if they are applied within root zones of non-target plants or if the chemical moves into the rootzone of non-target plants due to drainage issues. It is important to read all labels thoroughly to avoid applications that are not recommended on the label.

Information Links:

2013 Imprelis® Update: Tree Maintenance, Replacement, and Disposal (pdf file)

Imprelis® Update: 2012 Field Notes on Injury and Recovery (pdf file)

Tree damage from Imprelis: One year later - Michigan State University, 2012

A Homeowner's Guide to Suspected Imprelis® Herbicide Injury in the Landscape (pdf file)

A Turf Professional's Guide to Suspected Imprelis® Herbicide Injury in the Landscape (pdf file)

Imprelis® Herbicide Injury to Landscape Trees and Ornamentals (pdf file) - Office of the Indiana State Chemist

Avoid use of herbicide Imprelis, Purdue experts advise - Purdue University News Service - July 22, 2011

Herbicide damage on Spruce and Pine - Turf Tip - June 17, 2011

Stop sale order for Imprelis issued by the OISC (PDF) - Office of Indiana State Chemist - August 1, 2011

For additional information please refer to the Pesticide Section of the Office of the Indiana State Chemist website

Dupont website about Imprelis®

Click image to enlarge

Symptoms on Norway spruce growing near lawns treated with aminocyclopyrachlor

Symptoms on Norway spruce growing near lawns treated with aminocyclopyrachlor

Symptoms on white pine growing near lawns treated with aminocyclopyrachlor

Symptoms on Norway spruce growing near lawns treated with aminocyclopyrachlor

Symptoms on Norway spruce growing near lawns treated with aminocyclopyrachlor

 

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service