Pronamide (Kerb) is the most broad spectrum and widely used herbicide on leaf lettuce. It was first registered in 1969 by Rohm and Haas and was acquired by Dow AgroSciences in 2001. Until 2009 it was registered on all types of lettuce, endive, escarole and radicchio. The registration for leaf lettuce was removed in August 2009. Prior to this, the registration did not differentiate between the types of lettuce and most of the work done by Rohm and Haas to register this compound was done on head lettuce. The EPA now considers head and leaf lettuce to be in different crop groups requiring separate studies. The cancellation was the result of regulatory action by EPA and not because of any known problem with food safety or environmental contamination. It is still used on other leafy vegetables, including head lettuce, and was used safely for 40 years on leaf lettuce. The percentage of lettuce grown that is leaf lettuce has increased significantly and in 2009 about half of the lettuce grown here was leaf lettuce. This is the fourth season that Kerb will not be registered for leaf lettuce. Dow AgroSciences is committed to regaining this registration and has made a significant investment to develop the data needed by the EPA. There are two parts to regaining the leaf lettuce label: 1) A cancer reclassification of pronamide, the active ingredient in Kerb, and it’s metabolites is needed to make additional room in the risk cup. This makes it possible to register leaf lettuce, and 2) The EPA must establish a tolerance for leaf lettuce. Both of these are expected to be completed in mid to late 2014.

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To contact Barry Tickes go to: btickes@ag.arizona.edu.

For questions or comments on any of the topics please contact Marco Pena at the Yuma Agricultural Center.
College of Agriculture, The University of Arizona, Tucson, AZ.