Transcript Drift - Montana Pesticide Safety Education Program

Understanding Spray Drift
Reeves Petroff
Pesticide Education Specialist
Montana State University
Extension
http://mtpesticides.org
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
 Know the location of sensitive areas consider safe 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) tend to be
unpredictable and 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
Temperature increases
with height
Altitude
Cool Air
Increasing Temperature
Technical Aspects of Spray Drift
Warm Air
Recognizing Inversions:
 Under
clear to partly
cloudy skies and light
winds, a surface
inversion can form as
the sun sets.
 Under these
conditions, a surface
inversion will continue
into the morning until
the sun begins to heat
the ground.
Technical Aspects of Spray Drift
Precautions for Inversions:
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Surface inversions are common .
Be careful near sunset and an hour or so
after sunrise, unless…
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There is low heavy cloud cover
The wind speed is greater than 5-6
mph at ground level
5 degree temp rise after sun-up
Observe smoke or dust to
identify inversion conditions.
Technical Aspects of Spray Drift
Nozzles are important:
the amount – GPA.
Determine uniformity of application.
Affects the coverage.
Influences the drift potential.
Control
Technical Aspects of Spray Drift
Nozzles &
drift:
 Creating
smaller spray drops will result
in increased drift.
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 (m) =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
ASAE DSC and Volume Median Diameter (DV0.5)
From PMS* Laser Spectrometer
Droplet Spectra
Classification (DSC)
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Very Fine (VF)
Fine (F)
Medium (M)
Coarse (C)
Very Coarse (VC)
Extremely Coarse (XC)
Droplet Size
Range
< 182µm
183-280µm
281-429µm
430-531µm
532-655µm
>656µm
*USDA ARS
College Station, TX
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 means 0.3 gallons per minute 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 Droplet Movement with
Various Wind Speeds
Droplet
Sizes
(microns)
5 mph
Wind
10 mph
Wind
15 mph
Wind
20
mph
Wind
100
24 ft.
48 ft.
72 ft.
96 ft.
200
9
18
26
35
400
5
9
14
18
500
4
7
10
14
600
3
6
9
12
Boom height: 3 feet
Technical Aspects of Spray Drift
Evaporation of Droplets
High Relative Humidity
Low Temperature
Wind
Technical Aspects of Spray Drift
Low Relative Humidity
High Temperature
Nozzle Technology?
 Nozzles
designed to reduce drift
 Improved drop size control
 Emphasis on ‘Spray Quality’
Technical Aspects of Spray Drift
Spray Characteristics are
Important to Understand:
Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind
Technical Aspects of Spray Drift
XR Flat-fan @20, 40, 80 PSI
Boom
Drift
Technical Aspects of Spray Drift
Turbodrop XL @20, 40, 80 PSI
Strategies to Reduce Drift:
 Match
nozzle to target pest
 Increase flow rates - higher application volumes
 Use lower pressures
 Use lower spray (boom) heights
 Avoid adverse weather conditions
 Consider using buffer zones
 Consider using new technologies:
 drift reduction nozzles
 drift reduction additives
 shields, electrostatics, air-assist
Technical Aspects of Spray Drift
Some Other Things to Keep in Mind
when Planning a Spray Application
Allow enough time for:
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Scheduling and planning the application
Obtaining the products
Setting up the application date
Weather delays or maintenance problems, if
necessary.
Try not to fall into the trap of declaring “I
need to spray RIGHT NOW!”. Forcing a job
under poor conditions almost always leads to drift or
other errors.
Technical Aspects of Spray Drift
13%
23%
26%
38%
Applicator
Technical Aspects of Spray Drift
Nozzle
Nozzle
Applicator
Physical
Other
Thanks
Technical Aspects of Spray Drift