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Difference in NIS Brands? (07/16/15)

Question: Is there a difference in the quality of adjuvant between X NIS and Y NIS? I noticed that you listed both of them in the weed guide as an NIS. Does that mean that they are similar in activity or just classified as an NIS by the company?

Difference in NIS Brands?

Question: Is there a difference in the quality of adjuvant between X NIS and Y NIS? I noticed that you listed both of them in the weed guide as an NIS. Does that mean that they are similar in activity or just classified as an NIS by the company?

Answer:  Surfactants listed on page 126 in the ND Weed Guide are classified by their active ingredients and product label designation and information. Reputable surfactants do not show much difference in herbicide activity when herbicides are used at full label rates. A 1 pt/A rate of Roundup is considered a reduced rate. At that rate surfactants may increase herbicide activity on many weeds and have little effect on other weeds. As herbicide rates increase differences in activity of surfactants will decrease. A great man once said the best surfactant for Roundup is more Roundup.

You may want to consider the information shown in the table on page 71 in the electronic version of the ND weed control where we have tested some surfactants over many years.

Here is the link to page 71 in the weed guide.

http://www.ag.ndsu.edu/weeds/weed-control-guides/nd-weed-control-guide-1/wcg-files/a5-adjuvants

Several surfactants show good and consistent herbicide enhancement. We have not tested all surfactants on the market as the list is massive. It is difficult to interpret language indicating active ingredients on surfactant labels. It is also difficult to know which ingredients listed contribute to herbicide efficacy. One ingredient in many surfactants is nonylphenol ethoxylate (NPE) which makes surfactants very effective with herbicides. NPEs are also very toxic to aquatic organisms and have been targeted for possible elimination by the EPA (endocrine disruptor).

The mode of action of activator adjuvants are simplified into 3 areas:

  1. Retention – retain (stick) spray droplets on leaf foliage
  2. Deposition – decrease surface tension to some degree and deposit herbicide active ingredients on the leaf cuticle wax matrix to form a close interface
  3. Absorption – increase movement of herbicide active ingredients through leaf barriers and into the cytoplasm of the plant (systemic herbicides)

Surfactants influence mainly #1 above but have a role in all three actions.

Rich Zollinger

Extension Weed Specialist

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