Imprelis™ Technical Bulletin

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.

A. CHEMICAL CONUNDRUMS.

Navigating suspected chemical injury for green industry companies is challenging on many levels. This includes the diagnostic dilemmas we have already noted in this BYGL, and the many diverse communications issues that arise. Here are two examples of these challenges relative to questions that have emerged regarding Norway spruce, Black Hills and white pine injury and possible association with Imprelis herbicide applications.

First, according to James Belt, Agriculture Inspection Manager of ODA, the Ohio Administrative Code 901:5-11-02(D) indicates:

Pesticide applicators:

(4) Shall report to the department of agriculture:

(b) By written report within ten calendar days after learning of any property damage in excess of five hundred dollars resulting from or allegedly resulting from a pesticide used by the pesticide applicator or a trained service person, immediate family member or subordinate employee working under the pesticide applicator's direct supervision.

Ohio Revised Code 921.24: Prohibited Acts

No person shall do any of the following:

(Q) Refuse or fail to comply with this chapter, the rules adopted thereunder, or any lawful order of the director;

Secondly, Jim Chatfield recently met with Dr. John Lloyd, Chief Science Officer of the Rainbow Companies, based in the Twin Cities of Minnesota. John shared aspects of their communication with their customers from Rainbow Treecare President Greg Krogstad:

This week we have been receiving more calls regarding spruce [Norway and Black Hills] and pine damage due to Imprelis Herbicide. There was a letter sent out [to] Lawncare clients that we know have spruce and pine trees. Hundreds of companies have been using Imprelis this year so you may certainly see damage on properties. Lawncare will look at the property and talk with the client.

For now, we are not recommending anything for the declining trees. We have attempted [applications of] POM [Prescription Organic Matter]. We are waiting until DuPont instructs us on how to proceed. We will not remove the tree until we know what DuPont requires to support the claim.

The trees were not accidentally sprayed; it appears to be a systemic issue where roots are absorbing the compound. Newly planted, root-bound trees, do not appear to be impacted like mature, established trees. This is due to the application occurring over lawn areas and not under or around trees.

Please feel confident when discussing the Imprelis issue with clients. You may have some very upset clients. Remind them that the product was released in fall of last year and we waited before using it. All research showed Imprelis to be the least toxic, landscape friendly product on the market. It fits our commitment to low toxic, low input options and their property was not in any way a test site. We will correct the problems, but need to work with DuPont because they have responsibility in the matter.

As BYGL goes to press, John notes that the issue in the Twin Cities is now gaining local media attention.

These are just a few reminders that the green industry is a challenging business. As Joshua J. Marine noted: "Challenges are what make life interesting; overcoming them is what makes life meaningful."