Transcript Drift - Pesticide Safety Education Program

Understanding Spray Drift
Why Interest in Drift?
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Spotty pest control
Wasted chemicals
Off-target damage
More high value specialty crops
Less tolerant neighbors
Litigious Society
Result-higher costs-$$$
More wind?? (Timing)
Environmental impact
 Water and Air Quality
Public more aware of pesticides
(Negative) (Perceptions)
Urban sprawl
Technical Aspects of Spray Drift
The Drift:
 Creating
smaller spray drops will result
in increased drift.
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
Definition of Drift:
Movement of spray particles and
vapors off-target causing less
effective control and possible
injury to susceptible vegetation,
wildlife, and people.
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
drop size
evaporation
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.
 Do not spray at any wind speed if it is
blowing towards sensitive areas
 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
More drift at low Wind speeds?
 Because:
 Light
winds (0-3 mph)
- unpredictable & variable in ALL
directions.
 Calm & low wind conditions?
- temperature inversion
 Drift potential is lowest at wind
speeds between 3 and 10 mph (gentle
but steady breeze) blowing in a safe
direction.
Technical Aspects of Spray Drift
Wind Current Effects
Structures drastically 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
Inversions: Normal Conditions
Normal Temperature Profile
Air tends to rise
and mix with the
air above.
Droplets will
disperse and will
usually not cause
problems.
Technical Aspects of Spray Drift
Cooler
Temperature decreases
with height
Altitude
Warmer
Increasing Temperature
Temperature Inversions:
Temperature Inversion
Temperature increases as
you move upward.
Temperature increases
with height
Prevents air from mixing
with the air above it.
Altitude
Small suspended droplets
form a concentrated cloud
Cool Air
Move in unpredictable
directions.
Technical Aspects of Spray Drift
Increasing Temperature
Warm Air
Recognizing Inversions:
Technical Aspects of Spray Drift
Spray Droplet Size
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
Droplet Class
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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
Efficacy and Drift Potential is
Influenced by:
 Size
of the Spray Droplets Volume Median Diameter (VMD)
 Droplet Spectrum (Range - big to small)
Technical Aspects of Spray Drift
1/2 of spray volume = smaller droplets
VMD
1/2 of spray volume = larger droplets
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
Strategies to Reduce Drift:
 Select
nozzle to increase drop size
 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
Technical Aspects of Spray Drift