Transcript Drift - Purdue Pesticide Programs

Understanding Spray Drift
Robert E. Wolf
Extension Specialist
Biological and Agricultural Engineering
Why Interest in Drift?











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
Nozzle Technology?
 Nozzles
designed to reduce drift
 Improved drop size control
 Emphasis on ‘Spray Quality’
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
Will affect drift:
 Movement
of spray
particles off-target.
 Creating smaller spray
drops will result in
increased drift.
 Is
it Coverage vs Drift?
 What is the answer?
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




chemical
formulation
drop size
evaporation
Weather
 air
Equipment &
Application




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
However, Drift Potential May
be High at Low Wind Speeds
 Because:
 Light
winds (0-3 mph) tend to be
unpredictable and variable in direction.
 Calm and low wind conditions may
indicate presence of a 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 Speeds Gradients
11 mph
Height Above Crop Canopy, Feet
30
10 mph
20
8 mph
10
6
2
7 mph
Wind Speed
5 mph
0
The relation between height above the canopy of a
crop like cotton or soybean and the speed of wind.
Technical Aspects of Spray Drift
Wind Current Effects
 Wind
currents can drastically affect
spray droplet deposition
 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 Patterns Around Buildings
Ground
Diagram of wind around a building.
Adapted from Farm Structures*
* H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)
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:
Under normal
conditions air
tends to rise and
mix with the air
above. Droplets
will disperse and
will usually not
cause problems.
Technical Aspects of Spray Drift
Normal Temperature Profile
Cooler
Temperature decreases
with height
Altitude
Warmer
Increasing Temperature
Temperature Inversions:
Under these conditions
the temperature increases
as you move upward. This
prevents air from mixing
with the air above it. This
causes small suspended
droplets to form a
concentrated cloud which
can move in unpredictable
directions.
Technical Aspects of Spray Drift
Temperature Inversion
Temperature increases
with height
Altitude
Cool Air
Increasing Temperature
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
105 foot temperature monitoring tower
105’ 38°F
Cloud of 5-25 u oil
droplets generated under
unstable conditions
64’ 40°F
32’ 40°F
16’ 41°F
8’
41°F
Cloud is dispersing
2.5 mph wind
105’ 38°F
.5 mph wind
64’
32’
16’
8’
38°F
37°F
36°F
33°F
Shallow surface inversion
STABLE conditions up to 64’
NEUTRAL conditions at 105’
Technical Aspects of Spray Drift
Courtesy – George Ramsay, Dupont
Precautions for Inversions:


Surface inversions are common .
Be especially careful near sunset and an
hour or so after sunrise, unless…




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
Use of a smoke bomb or smoke
generator is recommended to
identify inversion conditions.
Technical Aspects of Spray Drift
Spray Droplet Size
Efficacy and Drift Potential is
Influenced by:
 Size
of the Spray Droplets Volume Median Diameter (VMD)
 Droplet Spectrum (Range - big to small)
% Volume in droplets less than
200 microns in size
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
1/2 of spray volume = smaller droplets
VMD
1/2 of spray volume = larger droplets
Technical Aspects of Spray Drift
Cutting Droplet Size in Half
Results in Eight Times the Number of Droplets
250
Microns
250
Microns
500
Microns
250
Microns
250
Microns
250
250
250
250
Microns Microns Microns Microns
Technical Aspects of Spray Drift
Important Droplet Statistics:
Operational
Area
Technical Aspects of Spray Drift
Evaporation of Droplets
High Relative Humidity
Low Temperature
Wind
Technical Aspects of Spray Drift
Low Relative Humidity
High Temperature
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
EPA Requested Changes Coming!!!!






Technical Aspects of Spray Drift
900
9
0
0
800
8
0
0
700
7
0
0
Example Reference Graph
E
x
a
m
p
l
e
R
e
f
e
r
e
n
c
e
G
r
a
p
h
very fine/ fine
fine/medium
v
e
r
y
f
i
n
e
/
f
i
n
e
medium/ coarse
f
i
n
e
/
m
e
d
i
u
m
coarse/
very
coarse
m
e
d
i
u
m
/
c
o
a
r
s
e
very
coarse/
extremely
c
o
a
r
s
e
/
v
e
r
y
c
o
a
r
s
ecoarse
v
e
r
y
c
o
a
r
s
e
/
e
x
t
r
e
m
e
l
y
c
o
a
r
s
e
600
6
0
0
XC
X
C
500
5
0
0
C
C
VC
V
C
400
4
0
0
Drop Size (microns)

New Label languageEPA Reviewing
Public Comments
Public ‘Listening
Sessions’ planned
Sometime in 2003??
Match the crop
protection product to
the target
Adhere to label
guidelines based on
an industry standard
 ASAE S-572
Buffer Zones or No
Spray Zones
Maximize Efficacy
Minimize Drift
DropSize(microns)

300
3
0
0
M
M
200
2
0
0
F
F
VF
V
F
100
1
0
0
0
0
0.1
0
.
1
0.5
0
.
5
Cumulative
Volume
Fraction
C
u
m
u
l
a
t
i
v
e
V
o
l
u
m
e
F
r
a
c
t
i
o
n
0.9
0
.
9
Origin Of Standardized Spray
Droplet Size Categories

1985 -- British Crop Protection Council (BCPC)
 Droplet
size classifications, primarily
designed to enhance efficacy.
 Uses the term SPRAY QUALITY for droplet
size categories.
2000 -- ASAE Standard S572
 Droplet
size classifications, primarily
designed to control spray drift.
 Uses the term DROPLET SPECTRA
CLASSIFICATION for droplet size
categories.
Technical Aspects of Spray Drift
ASAE DSC and Volume Median Diameter (DV0.5)
From PMS* Laser Spectrometer
Droplet Spectra
Classification (DSC)






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
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
In Conclusion:
Minimizing spray drift is in the best
interests of everyone. Do your part
to keep agrichemical applications on
target.
Technical Aspects of Spray Drift
Technical Aspects of Spray Drift