New Organic Herbicide Registration for California
Richard Smith, Farm Advisor
University of California Cooperative Extension, Monterey County

A new organic herbicide, Suppress, from Westbridge Company is now in the 30-day waiting period with the California Department of Pesticide Registration and should be fully registered by mid-February of 2015. The active ingredients are Caprylic and Capric Acids and were approved by the Organic Materials Review Institute (OMRI). It is a contact burn-down material that is registered for use in and around food crops including vegetables, trees and vines. I have tested it in trials conducted to screen materials for use with automated lettuce thinners that use a spray as the kill mechanism to remove unwanted lettuce plants and weeds http://cemonterey.ucanr.edu/files/201678.pdf. As a result, the weeds were young,14 to 21 days old in these trials. In addition, the trials conducted in 2013 and 2014 tested applications that were made at dawn when the plants were wet with dew to evaluate the efficacy of the materials under a worst-case scenario when the materials are probably diluted by moisture on the plants. In 2013, Suppress was tested at 12% v/v and provided excellent weed control to weeds 14 days after first germination water (FGW); control dropped off when applied at 21 days after FGW but it still had good weed control (Table 1). In 2014, Westbridge had finalized the label and Suppress was tested at the label rates of 3, 6, and 9% v/v with no additional spreader sticker at 14 days after FGW. It provided good weed control at1 and 7 days following the application. I have not yet tested Suppress on larger weeds, and it will be interesting to see how effective that it can be on larger, hard-to-kill weeds.