For immediate release

Release Date:    April 04, 2013

Contacts:         John E. Lloyd, Ph.D., Plant Health Doctors
                       (DrJohn@PlantHealthDoctors.com)

                     
                        Manuel J. Jordán, B.S., Hertitage Shade Tree Consultants    
                        (Manuel@heritageshadetree.com)

               

Tainted compost is an issue that should not be overlooked. 
Beware says EPA:  Is your compost safe, or will it damage your garden and landscape?

Many communities, golf courses and residential lawns were treated with Imprelis® herbicide in spring of 2011. Unfortunately, the herbicide kills and damages both needle bearing and leaf bearing trees.  It was removed from use by the EPA in 2011, but due to its persistence in the soil and in affected plant tissues it continues to be a problem in treated landscapes where the materials are recycled in lawn clippings as well as when treated materials are composted.  

The United States Environmental Protection Agency and State Pesticide Regulatory Agencies have strongly recommended against composting any grass clippings or landscape waste that had been treated with Imprelis® herbicide.  However, recommending and regulating are two different issues.

The State of Minnesota lifted the ban on depositing green wastes in landfills in 2012 to help landscape professionals and communities dispose of treated grass and debris for damaged and killed trees.  However, this opportunity to dispose of tainted materials was not well advertised.  Most landscape maintenance businesses in Minnesota were not even aware that they could landfill the waste.  So, the large majority of Imprelis® tainted plant and soil materials removed from landscapes made it into the traditional composting waste streams.

Why is Imprelis® in compost an issue? 

Imprelis®, common name aminocyclopyrachlor , is closely related to another herbicide called clorpyralid that was introduced in the early 2000’s.  Both products do not decompose in compost streams and can remain toxic to broad leaf plants when those plants come in contact with these composted materials. With clopyralid the EPA mandated that any residues that had been or were suspected to have been treated could not be composted¹. 

Since clopyralid was primarily used in turf farms, grass seed production systems and golf courses it was relatively easy for managers of those operations to follow the mandate created against composting contaminated materials.  The situation is not as easy with Imprelis®.  Imprelis® was distributed widely in the green industry and was used extensively by lawn care companies throughout the United States on both commercial and residential properties.  With such a broad source of application and such a broad range of applicators, it is more difficult for the EPA to work individually with commodity groups involved with using the herbicide. 

While Dupont, the manufacturer of Imprelis®, is diligently working with companies and residential landowners to compensate them for the extent of damage to impacted trees, the EPA has not mandated any testing or procedures for evaluating the potential for compost waste streams to be compromised.  This is even the case after professionals (university faculty and state regulators) throughout the United States warned about the potential for Imprelis® contamination of compost streams in 2011.²  But, either due to other distractions or industry pressures, the EPA has not followed up with regulation of either disposal or urban composting centers to protect the users of compost in the United States from this preventable issue.  At this point the message from our own environmental protection agency to users of composted materials seems to be “buyers beware.”³

So, how can we beware?  

There is no regulation making testing for Imprelis® residues mandatory at composting centers managed by either municipal or commercial contractors.  Most compost testing laboratories in the United States do not even offer the option for testing for Imprelis® herbicide residues.  Of those that do, it can be quite expensive, especially for homeowners or landscapers that may have to test repeatedly during the summer since they can’t store or use materials in bulk.  What you test and use today will not be the same materials you have available to use tomorrow.

We do know a couple of things that should help the average gardener, landscaper and homeowner.  Imprelis® was only used in landscapes in 2011 before it was removed from the market.  If you have compost that was started prior to 2011 and has not had any stock additions from lawn and landscape waste streams since, then you are probably OK.  If you compost your own yard wastes and never used Imprelis® (since it wasn’t available for homeowners to use) you are probably OK.  If your waste stream stock is only made up of agricultural wastes (cow manures and crop residues) you are probably OK.  

If you don’t know where your compost waste stream originates, and/or you use a community based formulation of compost, consider using another compost source for the next several years until we are guaranteed that any Imprelis® residues have been eliminated from the waste stream.  Also, if you are fortunate enough to have a commercial or municipal composter who actually tests for Imprelis® in their product, make sure the tested samples were actually taken from the stock of material you will be receiving.

Dr. Lloyd is the President of Plant Health Doctors, a Minnesota company dedicated to the environmentally sound management of healthy landscapes.

Mr. Jordán is an Instructor with Hennepin Technical College, Contract City Forester for Greenwood, Minnesota and a legal and environmental consultant with Heritage Shade Tree Consultants.

¹ http://www.puyallup.wsu.edu/soilmgmt/clopyralid.htm

² http://www.epa.gov/pesticides/regulating/imprelis.html

³ http://vanwert.osu.edu/licking/top-stories/update-on-herbicide-imprelis

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