Transcript Technical Aspects of Spray Drift

Understanding Spray Drift
Reeves Petroff
Pesticide Education Specialist
Montana State University
Extension
http://mtpesticides.org
Technical Aspects of Spray Drift
Why Interest in Drift?
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Spotty pest control
Wasted chemicals
 Result-higher costs-$$$
Off-target damage
 High value specialty crops
Less tolerant neighbors
 Urban sprawl
 Litigious Society
Environmental impact
 Water and Air Quality
Public more aware of pesticides
(Negative) (Perceptions)
Technical Aspects of Spray Drift
EPA Requested Changes Coming !?!?
 Guidance
to Chemical Manufacturers
 Matching the pesticide to the target
 More exacting label guidelines
 Buffer Zones or No Spray Zones
 Maximize Efficacy
 Minimize Drift
Technical Aspects of Spray Drift
Technical Aspects of Spray Drift
Definition of Drift:
Movement of spray particles and
vapors off-target causing less
effective control and possible
injury to susceptible vegetation,
wildlife, and people.
Adapted from National Coalition on Drift
Minimization 1997 as adopted from the AAPCO
Pesticide Drift Enforcement Policy - March 1991
Technical Aspects of Spray Drift
Types of Drift:
Vapor Drift - associated with
volatilization (gas, fumes)
Particle Drift - movement of spray
particles during or after the spray
application
Technical Aspects of Spray Drift
Factors Affecting Drift:
Spray
Characteristics
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chemical
formulation
evaporation
drop size
Weather
 air
Equipment &
Application
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nozzle type
nozzle size
nozzle pressure
height of release
movement (direction and velocity)
 temperature and humidity
 air stability/inversions
 topography
Technical Aspects of Spray Drift
Wind Direction:
 Wind
direction is very important
 Location of sensitive areas
 Consider buffer zones.
 If it is blowing towards sensitive areas –
STOP
 All nozzles can drift.
 Spray when breeze is gentle, steady, and
blowing away from sensitive areas.
 “Dead calm” conditions are never
recommended.
Technical Aspects of Spray Drift
What ‘n’ Why?
 Because:
 Light
winds (0-3 mph)
unpredictable & variable in
direction.
 Calm & low wind conditions?
- temperature inversion
 Drift potential is lowest
 3 and 10 mph
 gentle but steady breeze
 blowing in a safe direction.
Technical Aspects of Spray Drift
Wind Current Effects
Wind
currents can affect spray
droplet deposition
Structures affect wind currents
 Wind breaks
 Tree lines and orchards
 Houses and barns
 Hills and valleys
Technical Aspects of Spray Drift
Wind Patterns Near Treelines
Adapted from Survey of Climatology:
Griffiths and Driscoll,
Texas A&M University, 1982
Technical Aspects of Spray Drift
Wind Meters and Compass
Name
Features
Cost*
Dwyer
Floating Ball
15.50
Wind Wizard
Mechanical
39.50
Turbo Meter
Wind speed - knots, feet/min, meters/sec, mph
135.00
Kestrel 1000
Maximum, average, current wind speed
- knots, feet/min, meters/sec, mph
89.00
Kestrel 2000
Maximum, average, current wind speed, temp,
wind chill- knots, feet/min, meters/sec, mph
119.00
Kestrel 3000
All wind speed features plus temp, wind chill, dew
point, heat index, relative humidity
159.00
Plastimo Iris 50**
Compass
89.00
*Prices for Wind Meters taken from Gempler’s 2000 Master Catalog
**Plastimo Airguide Inc., 1110 Lake Cook Road, Buffalo Grove, IL 60089(708-215-7888)
Technical Aspects of Spray Drift
Normal Conditions
• Air rises
• Mixes with air
above.
• Droplets will
disperse
• Usually no
problems.
Normal Temperature Profile
Cooler
Temperature decreases
with height
Altitude
Warmer
Increasing Temperature
Technical Aspects of Spray Drift
Temperature Inversions:
• Temperature increases
with altitude.
• Prevents air from mixing
with the air above it.
• Small suspended drops
form a concentrated cloud
• Moves in unpredictable
directions.
Temperature Inversion
Warm Air
Altitude
Cool Air
Increasing Temperature
Technical Aspects of Spray Drift
Recognizing Inversions:
 Clear
to partly
cloudy skies
 Light winds
 Inversion can form
as the sun sets.
 Continues into the
morning until the
sun begins to heat
the ground.
Technical Aspects of Spray Drift
Precautions for Inversions:
Surface inversions are common .
 Be careful near sunset and an hour
or so after sunrise, unless…
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 Low
heavy cloud cover
 Wind speed > 5-6 mph
o
 5 temp rise after sun-up
 Observe
smoke or dust to
identify inversion conditions.
Technical Aspects of Spray Drift
Nozzles &
drift:

Creating smaller spray drops will result in
increased drift.
 Nozzle tip
 Weather
Technical Aspects of Spray Drift
Spray Droplet Size
Size Matters!
All nozzles produce a wide range of
droplet sizes
Big to small
Technical Aspects of Spray Drift
Relationship of Drift to Drop Size
One micron (um) =1/25,000 inch
Technical Aspects of Spray Drift
Comparison of Micron Sizes for
Various Items: (approximate values)
pencil
lead
2000 (m)
paper
clip
850 (m)
150
toothbrush
bristle
sewing thread
420 (m)
300 (m)
150 (m)
human
100 (m)
staple
hair
Technical Aspects of Spray Drift
Is Drift Bad?
Are all small
droplets bad?
Technical Aspects of Spray Drift
Nozzle Drop Size Classes
Very Fine to Fine
< 200 um
Medium to Coarse
200 to 450 um
Very Coarse > 450 um
Technical Aspects of Spray Drift
Technical Aspects of Spray Drift
8003 tip
80 means 80o fan
03 = 0.3 GPM at 40 psi
(38 ½ ounces per minute)
Technical Aspects of Spray Drift
Tip Spray Selection by Drop
Size
Turbo TeeJet Flat-fan
Technical Aspects of Spray Drift
Spray Characteristics are
Important to Understand:
Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind
Technical Aspects of Spray Drift
Evaporation of Droplets
High Relative Humidity
Low Temperature
Low Relative Humidity
High Temperature
200 um
Wind
100 um
Technical Aspects of Spray Drift
Nozzle Technology?
 Nozzles
designed to reduce drift
 Improved drop size control
 Emphasis on ‘Spray Quality’
Technical Aspects of Spray Drift
Turbodrop – A.I.
XR Flat-fan
20 PSI
40 PSI
Boom
Small
Drops
Technical Aspects of Spray Drift
80 PSI
20 PSI
40 PSI
80 PSI
Strategies to Reduce Drift:
 Match nozzle to target pest
 Larger application volumes - GPA
 Use lower pressures
 Use lower spray (boom) heights
 Weather?
 Consider using buffer zones
 Consider using new technologies:
 drift
reduction nozzles
 drift reduction additives
 shields, electrostatics, air-assist
Technical Aspects of Spray Drift
13%
23%
Nozzle
26%
38%
Applicator
Technical Aspects of Spray Drift
Nozzle
Applicator
Physical
Other
Thanks
Technical Aspects of Spray Drift