Getting the Most Out of
Glyphosate and Other Sprays: Fruit growers
often apply a post-emergent herbicide beneath the tree or vine row
in
spring to control
winter annuals and other weeds. Often a pre-emergent herbicide is included in this application.
Glyphosate (Roundup) is a
post emergent
systemic herbicide that is widely used for this first weed spray.
In order for
glyphosate to be effective, it needs to be
absorbed into the plant. In soft water glyphosate
has no problems in being absorbed. However in hard water glyphosate will be 'tied up'
and not absorbed
as readily. Hard water, common in many parts of Indiana, contains high
concentrations of soluble salts, calcium and magnesium. When these cations are present they react with the negatively
charged glyphosate to form compounds that are not readily absorbed by
plants.
This results
in poor uptake and poor weed control. The solution to the hard water problem is to add ammonium sulfate to the spray
water before
mixing with
glyphosate. Ammonium sulfate ions tie up the calcium and magnesium ions forming conjugate salts. Additionally, some of
the
glyphosate
reacts with ammonium to form a compound that some weeds preferentially absorb. Follow the Roundup label
recommendations on the
amount of
ammonium sulfate to add. Another problem associated with spray water quality is that many fungicides and insecticides
break down
quickly in
high pH water. Captan, Cygon, Imidan, Kelthane, malathion, and Omite are examples of compounds that are especially
vulnerable to
alkaline
hydrolysis. The addition of about 2
ounces of food grade citric acid per 100 gallons of water will lower the pH from about 8.0 to
about 5.5.
Here is his contact information:
Bruce Bordelon, 1165 Dept. of
Horticulture and Landscape Architecture,
Purdue University, West Lafayette, IN
47907-1165, 317/494-8212,
Hope
this helps,
Brian
Sheridan, IN
Hello,
There was talk a while back
about (cannot remember name of the stuff)
dusting fruit trees to present a
barrier to insect damage. My question
is; Would calcium disolved in
the water present a similar barrier?
In our area we have the second
hardest water in Ontario, and when it dries
it leaves a white film.
Doesn't matter if it is a car being washed or the
foliar feeding of a
plant, lots of calcium in the water, ALWAYS a film
when it
dries.
After reading the postings regarding water PH and chemcial half
lifes, I
decided not to use our hard well water for my limited spraying,
and buy
water that was pure for chemical spraying.
Now I am
wondering if I should not spray chemicals with the "clean" water,
and later
spray with our "calcium" water to add a white film barrier.
Anyone have
any experiece with very hard water and
spraying?
Thanks,
Tom
--
Thomas Olenio
Ontario,
Hardiness Zone 6a
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