Imprelis, from DuPont™, is a systemic, broad-spectrum, selective broadleaf herbicide for use in lawn care operations.  The active ingredient is Potassium salt of aminocyclopyrachlor.  This new lawn care herbicide was registered for use in 2010 and was widely-used in many markets across the US in 2011.  Its mode of action is by foliar and root uptake.  Its formulations allow applications as a liquid spray or as a granule.  It provides good control of several persistent perennial weeds such as wild violets and ground ivy.  An added characteristic of this herbicide is that it also provides efficacy when applied during periods of rainfall.  It is effective at very low use rates of 0.07 lb active ingredient/acre or 4.5 oz/Acre.  On fertilizer granules the use rate is 0.07 – 0.1 lb ai/acre.

Within the past few weeks (late May/early June), there have been several reports of plant damage on properties that received an Imprelis application in April.  At present, the plants most affected have been Norway spruce (Picea abies) and white pine (Pinus strobus).  Blue spruce (Picea pungens) trees may also be affected but there have been fewer reports of damage.  Moderate to large trees have exhibited damage to varying degrees and seen as twisting and curling (epinasty), discoloration/blanching, and browning of the newer growth (as seen in pictures below).  There is also some damage suspected on other landscape ornamental plants such as Honeylocust, Taxus, and arborvitae.

The Ohio Lawn Care Association is working towards collecting as much information as possible regarding suspected plant damage following Imprelis applications.  While much is yet unknown, we will strive to keep our membership and the Green Industry at large informed as to developments on this topic.  Please see additional resources available here and by following the hyperlinks to several university updates below.  OLCA will continue to monitor developments and update this site frequently.