Glyphosate is the most widely used herbicide in Arizona, the USA and worldwide. That may be coming to an end and it is probably not too early to start to consider alternatives. Glyphosate was developed in the early 60’s as an industrial solvent to clean pipes and boilers. Monsanto registered it as a herbicide in 1974 and sold it for around $100/gal. It now sells for $30 to $50/gal and is used by people everywhere. It has fallen in popularity in recent years for a couple reasons: 1) A couple lawsuits were decided last year in favor of a groundskeeper and a homeowner who claimed they had contracted cancer as a result of glyphosate use and thousands of similar lawsuits are now underway even though the EPA has found it to be safe., and 2) More than 40 separate weed species have been identified that have developed resistance to Glyphosate over the last 40 years. This has caused serious problems in many parts of the country. Only one species, palmer amaranth, has been identified in Arizona and careful management is needed to avoid more. Some counties and some municipalities have already banned the use of glyphosate. The reason why Glyphosate is so popular in commercial agriculture are that 1) it is systemic and effective on most weeds including those that have become well established, 2) It is used postemergence to the weeds and has little soil residual activity and will not hurt most crops that are planted soon after application and 3) it has been off of patent for several years is relativity affordable and 4) It is not volatile and will not drift to sensitive crops in the vicinity There are not many herbicides that have these same characteristics. There are several contact herbicides that are broad spectrum with little soil residual and are not volatile, but they are normally only effective on small seedlings Several are used in combination with Glyphosate, but they are can be inconsistent when weeds get beyond the seedling stage. These include bromoxynil (Buctril, Maestro), Paraquat (Gramoxone), Pyraflufen (ET), Carfentrazone (Aim, Shark) Caprylic acid (suppress), Pelargonic acid (Scythe) and others. Some have soil activity (Goal and Chateau). The Plant growth regulators like Dicamba (Clarity), 2,4-D and MCPA are volatile and dangerous to use around many crops. We will be conducting trials this year to find alternatives to that are used postemergence and have the same characteristics as Glyphosate. Our trials will focus on postemergence weed control, soil residual and volatility. So far, our list is fairly short and includes Glufosinate, (Rely, Liberty, Finale, Cheetah), Indaziflam (Alion, Specticle, Marengo), and Pyroxasulfone (Zidua), We would like suggestions so that we can expand this list. Please contact myself (btickes@ag.arizona.edu) or Marco (marco@ag.arizona.edu) if you have suggestions.

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.