Comments in Response to DCPA Use on Sweet Potatoes

Date: April 25, 2005

To: Dr. Michael Kawate
Cathy Tarutani
Department of Plant and Environmental Protection Sciences
3190 Maile Way, St. John 307
University of Hawaii
Honolulu, HI 96822

From: Jill Bloom
Office of Pesticide Programs
EPA

Subject: comments on Federal Register Notice (Docket# OPP-2005-0024)

Dear Dr. Kawate and Ms. Tarutani,

Hi! I am the Chemical Review Manager for DCPA, and I have reviewed your comments on certain use sites, proposed for termination, for which you would like to retain the use of DCPA. We have taken your comments into consideration, and are trying to determine the most appropriate course of action. As part of that determination, I would like to confirm your thoughts about the use of DCPA on the use sites you discuss in your comments and see if you can provide any insights about water contamination with degradates of DCPA. First, I would like to explain the rationale for our proposal to terminate the subject uses.

It was not our intention to terminate uses which are critical to crop production, but rather to reduce the loading of groundwater with the DCPA-metabolite, TPA. Although the Agency has not identified a health endpoint associated with exposure to TPA, we are concerned about modeling which indicates a strong potential for TPA, from the use of DCPA, to contaminate drinking water and water natural resources. The modeling is supported by the prominence and degree of contamination with TPA we have observed in groundwater monitoring studies and reports. To address our concerns abut water contamination, the manufacturer agreed to request termination of a number of use sites, most notably residential turf and ornamentals, potatoes, and cotton. The manufacturer also proposed termination of a number of other use sites with much less usage, based on the input of their own marketing people, The Agency also sought information on which uses of DCPA were critical, this time based on input from USDA and State Extension specialists. From this input, the list of use sites for termination was developed.

We acknowledge your assessment of the critical need for DCPA on sweet potato, and understand that you believe that use should be retained. We also acknowledge your comments on the potential effect the loss of DCPA may have on the culture of beans, bean yam, cucumber, eggplant, and turnips in Hawaii. We would like you to clarify—is it your wish that the Agency reconsider the termination of these uses of DCPA also, or is the use of DCPA less critical problem for them? In addition, although your comments mention that weed control in sweet potato depends on alternating treatments of DCPA and Devrinol, we would like to know if that is the limit of controls available, or if mechanical controls are feasible, and whether mechanical controls or herbicides other than DCPA can be used to the desired effect in beans, bean yam, cucumber, eggplant, and turnips.

Of the crops you mention, only the continued use of DCPA on turnips has been requested in another comment on the Federal Register notice. Do you have an opinion on whether the use of DCPA in Hawaii on sweet potato, beans, bean yam, cucumber,and eggplant might best be made available to Hawaii as a Special Local Need (SLN) registration? Such an SLN would enable us to terminate those uses elsewhere, while allowing the use in Hawaii. We might even be able to arrange that the regular Section 3 uses would be retained until such time as Hawaii obtains an SLN.

Probably most important, since we are lacking information on the contamination of Hawaiian waters (particularly groundwater) with TPA, we want to make sure we take the right approach in balancing the critical nature of these uses to Hawaiian agricultue and the potential for drinking water and groundwater contamination with TPA in Hawaii. Any insights you may have on this last issue would be very helpful to us as we develop our course of action.

Thank you in advance for any commentary you can provide.

Jill Bloom, Review Manager
US Environmental Protection Agency
Office of Pesticide Programs
Special Review and Reregistration Division
Phone: (703) 308-8019
Fax: (703) 308-8041