Is There Really a Difference Among Adjuvants

Adjuvants are unregulated and are not required to be labeled with
the EPA. This creates an "open field" for companies to produce
and distribute their own series of adjuvants. As a result, there
are literally thousands of adjuvants on the market which creates
confusion and frustration to the grower in trying to decide which
adjuvant should be used with each herbicide or tankmix and under
different environmental conditions. Adjuvants could be tested as
is done by "Consumer Report," but each production batch may be
different and a company can change the ingredients or proportion
of ingredients without notifying the user because they are
unregulated. As a result the material used one year may not be
the same as the product used in another year.

There are limitations in creating the "perfect adjuvant". NDSU
research has shown significant herbicide enhancement from
methylated seed oil (MSO's) adjuvants with many classes of
herbicides. However, MSOs should not be used with Roundup or
Cobra. Several other factors make adjuvant selection difficult:  


1. Some adjuvant labels do not define chemical composition.   

2. Adjuvant labels make vague, unverifiable claims and even   
   contradict pesticide labels. 
 
3. Altering surface characteristics (wetting, sticking,  
   spreading, etc.) vary greatly between adjuvants and often DO 
   NOT correlate with herbicide enhancement. 

4. Components labeled as active ingredients (ai) in adjuvants   
   are not recognized universally. This would then alter the   
   percentage of ai as stated on each adjuvant label. 

5. Surfactant Hydrophilic:Lipophilic Balance (HLB) does not   
   always correlate with herbicide enhancement.

There is a need to standardize adjuvant labels and create a more
uniform method in which labels are written and active ingredients
disclosed. The Canadian herbicide and adjuvant companies are
solving the problem of adjuvant selection by testing and
selecting the superior adjuvant with each herbicide and then
packaging that superior adjuvant with the herbicide. The user
would have no choice in adjuvant selection because the adjuvant
comes in the same box as the herbicide. Some companies in the
U.S. (i.e. DuPont) produce bulletins stating guidelines to
qualify adjuvants for use with specific herbicides.  

The following table shows 1995 data from Roundup applied at about
3 fl oz/A (4 fl oz = 0.25 pt) applied with various adjuvants.
Wide ranges of control were observed with each weed species
evaluated. Research was conducted at Williston and Hettinger, ND
where humidity is less and weed control would be decreased making
adjuvants more critical in herbicide enhancement.

Control was greatest with Impressive, Class Act, or Surfate II
which are all ammonium sulfate + surfactant mixtures. Highest
control can be achieved by selecting the superior adjuvant, using
a good ammonium sulfate + surfactant premix product, and by
increasing the Roundup rate. This information is important in
using Roundup as a preharvest burndown, for fall annual and
perennial weed control, for spring preplant weed control, and for
use on many genetically alter crops available in the future in
which Roundup can be used. 

Yes, there is a difference among adjuvants - All Adjuvants Are
NOT Created Equal!