Adjuvants for Vegetable Herbicides (March 19, 2014)

An adjuvant is a substance that is in a herbicide formulation or added to the spray tank to modify herbicidal activity or application characteristics. These can be divided into spray modifiers which include spreaders and stickers, anti-foaming agents, drift control agents and others that are used to alter the physical characteristics of the spray solution and activator agents which include surfactants (surface active agents), Crop oil concentrates and water conditioners including fertilizers. Some adjuvants are included in the formulation by the manufacturer and some are required to be added to that spray tank by the applicator. There are thousands of products on the market and many of them include more than one type of adjutant. Applicators are commonly confused by all of these and the diverse uses that they were developed for. There are not many herbicides registered for use on vegetable crops and most of them use pre-emergence herbicides. Adjuvants are generally used only with post emergence herbicides. There are some people who think that adjuvants can be useful with pre-emergent herbicides but in seven trials we have not found evidence of this. At the risk of oversimplification, the following chart is intended to help with some of the confusion associated with this subject. It includes only postemergence herbicides registered for use in the production of vegetable crops.

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