20 Arbor Age / May 2014 www.arborage.com
Herbicide applicators are trained to know the infl uence
that certain factors can have on the effectiveness of the appli-
cation — things like application timing, equipment calibration
and selection of the proper herbicide for the vegetation being
treated. One factor often overlooked is water quality.
Water is often 95 percent or more of the total herbicide
spray solution. So it makes sense that water quality could im-
pact the effectiveness of the herbicide application.
This was the focus of a publication by Purdue Pesticide
Programs, a function of the Purdue University Cooperative
Extension Service. The publication is titled The Impact of Water
Quality on Pesticide Performance.
Poor water quality can have adverse effects
What kind of problems can poor water quality cause in a
herbicide solution? For one, if water contains high levels of
acidity and/or dissolved minerals, these may interact with the
active and/or additive ingredients in the herbicide formulation.
Poor-quality water also can adversely infl uence the herbicide
by reducing the solubility and decreasing absorption by the
target plant, resulting in poor performance.
These problems might not always drastically reduce perfor-
mance, but even a slight drop may be enough to cause signifi -
cant control issues when treating particularly diffi cult species,
or species that are tolerant to certain herbicides. And if this
happens, water quality often is overlooked as the culprit. The
immediate suspects are factors such as improper tank-mixing,
poor weather conditions at the time of application or perhaps
the herbicide used.
The importance of testing water
The Purdue publication makes the case for testing
your water before making a tank mix. Things to mea-
sure include iron levels, pH and water hardness. There are
essentially two options for testing your water: Hire a pro-
fessional vendor or purchase a do-it-yourself water-testing
kit. The route selected probably will be influenced by the
water source.
If an operation is getting the majority of the water used
in applications from the same main source, it's fairly simple to
bring in a professional to determine the water quality before
the season starts.
Selecting the do-it-yourself testing route makes more sense
for those who are using multiple water sources from various
The Impact
Water
Quality Can
Have on
Herbicide
Performance
HERBICIDES HERBICIDES
