Spot treatments call for care and calibration.
T
he popularity of backpack sprayers
and ATV-mounted spray rigs has fed
the fast-rising interest in spot-spraying
weeds.
Catching new infestations early
is a smart, low-cost and convenient
way to maintain grazing lands. But
treating relatively small areas and
applying small amounts of product
still requires responsible, proper
application. Often that requires a
more complex answer to a simple
question. For example:
Q. How much Product X do I put in
my 2-gallon hand sprayer?
A. How much spray volume are you
applying with your particular spray
equipment and spraying style?
Answering a question with another
question may make us a bunch of
wiseacres, but without calibration,
there are no answers. Fortunately,
there’s a simple step-by-step procedure
to determine your individual spray
volume and then how much product
— Opensight® herbicide in this
example — to add to your sprayer:
Step 1. Clean your sprayer and
nozzle thoroughly. Then fill the spray
gallons of water. Find your spray
volume in gallons per acre calculated
above and read across the table to
determine the amount of Opensight
to use based on the recommended
application rate. Remember:
Opensight is a dry formulation.
tank with clean water. Make sure the
nozzle forms a uniform spray pattern.
Step 2. Measure an area 18½ feet by
18½ feet, which equals ¹⁄128 of an acre.
If possible, this should be done in the
area where you will be spraying.
Step 3. Time the number of seconds
it takes to spray the measured area
uniformly with water by using a sideto-side sweeping motion with the spray
wand. Think of it as spray-painting the
measured area. Record the number
of seconds required to spray the area.
During application, be sure to maintain
a constant sprayer pressure. It will take
about four to six passes through the
area for complete coverage, and you
should repeat this step at least twice,
making sure the results are consistent
to calculate an average time.
Step 4. Spray into a container while
maintaining constant pressure for the
average time calculated in Step 3.
Step 5. Measure the number of
fluid ounces of water in the bucket.
This amount is equal to the number of
gallons per acre the sprayer is delivering.
Step 6. Use Table 1 to determine
how much Opensight to add to 2
Example
You have completed the calibration
procedure and applied 40 fluid ounces
in the measured area. Thus, with your
particular spraying style, you can
expect to apply a spray volume of 40
GPA. Now, you’ve determined you
want to apply the 2½-ounce-per-acre
rate of Opensight. Referencing Table 1,
the amount of Opensight® herbicide
needed for your GPA and the 2½-ounce
application rate is 1¼ teaspoons. Add
1¼ teaspoons of dry product (it doesn’t
take much) into 2 gallons of water plus
2 tablespoons of a quality agricultural
surfactant. Make sure the herbicide is
in solution with agitation. Shake the
backpack periodically to maintain
solution. Use Table 2 to determine how
much ForeFront® HL herbicide to add
to 3 gallons of water plus 3 tablespoons
of surfactant. Table 1. Amount of Opensight® Herbicide (in tsp.) to Mix in 2 Gallons of Water (1 tsp. = 0.1 oz. of Opensight)
Desired
Application Rate
of Opensight
(oz. dry product/A)
20 GPA
tsp.
20 GPA
oz. prod.
30 GPA
tsp.
30 GPA
oz. prod.
40 GPA
tsp.
40 GPA
oz. prod.
50 GPA
tsp.
50 GPA
oz. prod.
60 GPA
tsp.
60 GPA
oz. prod.
Water Volume in GPA
2 oz./A
2.00
0.20
1.33
0.13
1.00
0.10
0.80
0.08
0.67
0.07
2.5 oz./A
2.50
0.25
1.67
0.17
1.25
0.13
1.00
0.10
0.83
0.08
3.3 oz./A
3.30
0.33
2.20
0.22
1.65
0.17
1.32
0.13
1.10
0.11
Table 2. Amount of ForeFront® HL Herbicide (in fl. oz.) to Mix in 3 Gallons of Water
Desired
Application Rate of
ForeFront HL
(pt. product/A)
20 GPA
fl. oz. prod.
30 GPA
fl. oz. prod.
40 GPA
fl. oz. prod.
50 GPA
fl. oz. prod.
60 GPA
fl. oz. prod.
70 GPA
fl. oz. prod.
80 GPA
fl. oz. prod.
90 GPA
fl. oz. prod.
100 GPA
fl. oz. prod.
1.2 pt./A
2.9
1.9
1.4
1.1
1.0
0.8
0.7
0.6
0.6
1.5 pt./A
3.6
2.4
1.8
1.4
1.2
1.0
0.9
0.8
0.7
2.1 pt./A
5.1
3.4
2.6
2.0
1.7
1.4
1.3
1.1
1.0
Water Volume in GPA
Label precautions apply to forage treated with ForeFront HL and to manure from animals that have consumed treated forage within the last three days. Consult the label
for full details.
4
®Trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow. When treating areas in and around roadside or utility rights-of-way that are or will
be grazed, hayed or planted to forage, important label precautions apply regarding harvesting hay from treated sites, using manure from animals grazing on treated areas
or rotating the treated area to sensitive crops. See the product label for details. State restrictions on the sale and use of Opensight apply. Consult the label before purchase
or use for full details. ForeFront HL is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for
sale or use in your state. Always read and follow label directions.