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Calibrating a Backpack Sprayer August 23, 2019
Scott Wanzor: [email protected] /// 404-434-4442
Coastal Georgia Botanical Gardens
Savannah, GA
Since everybody here loves math…… Here are 3 slides on the value of understanding knowing how to calibrate a backpack or pump-up
sprayer and how that knowledge can save you money!
Calibration
1 gallon of water covers how many square feet?
Calibration: Backpack
• Know your water volume per 1,000 ft2
• Always double check rates of pesticide
Correct Example… (Slide 1 of 2 slides…)
• Label says to apply 3 oz. 1,000 ft2: - Amount of water you apply per 1,000 ft2 = 2 gallons - 3 gallon backpack sprayer
- Will cover 1,500 ft2 (3 gals water divide by 2 gals/1,000 ft2)
- Therefore: Mix 4.5 oz. of herbicide in this backpack (3 oz./1,000 ft2 x
1,500 ft2 …or… 3 x 1.5)
Calibration: Backpack
Incorrect example: (Slide 2 of 2 slides…)
• Label calls for 3 oz./1,000 ft2 - 3 gallon backpack sprayer
- You mix 3 oz. x 3 gallons of water (3 oz. for each gallon of water)
- 9 oz. of herbicide
• Correct amount of herbicide is 4.5 oz. per 3
gallons. 9 oz. is double the rate on the label! 1) Excellent weed control!
2) Off label use!
3) Paid twice too much $$$!
Liquid applications:
Do you use backpacks?
Flat fan nozzles should only be
held in a stationary position while
spraying.
Attached to a
backpack
sprayer
Spray wand held correctly,
non-swinging arm motion
providing a flat band pattern
Spray wand turned sideways
“swinging arm motion” resulting
In a zig zag pattern.
Slide of Spray Techniques Used For Training of Applicators
Glyphosate mis-application
Uniform weed or insect control?
High Pressure
Spray Wand High pressure, high volume nozzle,
spray wand used in Florida
200 psi pressure?
So it floats?
Drying Patterns
Flat fan nozzle
turned sideways
using a “swinging
arm motion”
Initially the
pattern appears
uniform
Zig Zag pattern
is starting to
show
Over application in
others areas can
result in injury.
Drying Patterns
Uneven pattern--
under application
can result in poor
control
Over
Application
As the spraying
pattern continues
to dry, under
application
becomes more
obvious.
Drying Patterns
Uniform weed or insect control?
Flat Fan
Misapplication
High pressure, large nozzle
spray wand used with a
swinging arm motion
Drift versus Volatility
Huge, fundamental difference!
Drift • Definition: Spray droplets – However small
• Droplet size: Smaller more likely to drift
– Pressure
– High volume
– Low volume
• Wind moves fine droplets
• Spray tip height
• Operating speed
• Air temperature & Humidity
Volatility
• Definition: Gas or vapor of the chemical
• Amine:
– Water-based
– No volatility
• Esters:
– Oil or solvent-based
– Some new technology: Low volatile esters
– Many years ago esters were much more
volatile
Fine Droplets
Large Droplets
Misapplications
Uniform weed or insect control??
Spray Nozzle
Wear
No Wear
Some Wear Heavy Wear
CALIBRATION
CALIBRATION
CALIBRATION
Calibration
CANNOT
keep calibrated
—Adjustable—
Spray Rate
vs
Spray Volume
RATE: Per 1,000 Square Feet
What happens when a high rate of
herbicide is mixed or applied
incorrectly?
CORRECT
RATE OF
HERBICIDES
ARE VERY
IMPORTANT!
Pressure
Regulators
Calibrating a Backpack Sprayer August 23, 2019
Scott Wanzor: [email protected] /// 404-434-4442
Coastal Georgia Botanical Gardens
Savannah, GA