Keys to Spray Drift Management
Robert E. Wolf
Extension Specialist Application Technology
Biological and Agricultural Engineering
Why Interest in Drift?
Spotty pest control
Wasted chemicals
Off-target damage
More high value specialty crops
Urban sprawl and.....
Less tolerant neighbors
Litigious Society
More wind?? (Timing)
Environmental impact
• Water and Air Quality
 Public more aware of pesticide
concerns! (Negative) (Perceptions)
 Result-higher costs-$$$
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Spray Droplet Management!
 Need knowledge of the product being used.
 Herbicide, Fungicide, Insecticide
• Systemic
• Contact
 Uniform coverage.
 Is it Coverage vs Drift?
$64,000 Question?
 What is the answer????
Efficacy and Drift Mitigation:
Droplet Spectrum (Range - big to small)
Size of the Spray Droplets - Microns
Volume Median Diameter (VMD)
% Volume in droplets less than
200 microns in size
Drop Size:
One micron (m) =1/25,000 inch
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
Types of Drift:
Vapor Drift - associated with
volatilization (gas, fumes)
Particle Drift - movement of spray
particles during or after the spray
application
Factors Affecting Drift:
Spray Characteristics Equipment & Application

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chemical
formulation
drop size
evaporation
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nozzle type
nozzle size
nozzle pressure
height of release
Weather
 air
movement (direction and velocity)
 temperature and humidity
 air stability/inversions
 topography
Weather factors of concern:
 air movement
(direction and velocity)
• Topography, etc.
 temperature and humidity
 air stability/inversions
Courtesy – George Ramsay, Dupont
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.
Determining wind direction:
 Compass
• Provide magnetic description
• Direction blowing from
• Into your face!
Drift Potential: 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.
Wind Speeds: Spray Droplet Movement
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
Wind Speeds Gradients:
Height Above Crop Canopy, Feet
30
20
10
6
2
11 mph
10 mph
8 mph
7 mph
5 mph
0
The relation between height above the canopy of a
crop like cotton or soybean and the speed of wind.
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
Wind Patterns Near Treelines:
Adapted from Survey of Climatology:
Griffiths and Driscoll,
Texas A&M University, 1982
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)
Wind Patterns Around Buildings:
Overhead
View
Wind
Diagram of Wind Around a Building
Adapted From Farm Structures*
* H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)
Determining wind speeds:
 Handheld devices
• Mechanical - floating ball, wind vane
• Electronic – spinning turbines
 In-the-field stations
 On-the-go stations
Handheld windmeters:
Weather stations with anemometers:
Weather station in use:
Enabling technology:
 GPS (Global Positioning System)
 Increased computing power in
smaller packages
 Ability to transfer data to
computers
On board weather instrumentation:
 Aventech Research Inc.
• Aircraft Integrated Meteorological
Measurement System –AIMMS
 AIMMS-10
 AIMMS-20
 Air flow probe
 2 - measurement modules
 CPU (20 second updates)
 Wind speed and direction
transmitted on-board
• Used and logged
• PDA software available for real
time display of meteorological
conditions.
http://www.aventech.com
On board weather instrumentation:
www.ambientweather.com
www.specmeters.com
Web sites of interest:
www.aventech.com
www.ambientweather.com
www.benmeadows.com
www.brunton.com
www.davisnet.com/weather/index.asp
www.gemplers.com
www.onlinemarine.com
www.oregonscientific.com
www.scientificsales.com/constat.htm
www.specmeters.com
www.westmarine.com
Brand names appearing in this presentation are for identification purposes only. No
endorsement is intended, nor is criticism implied of similar products not mentioned.
Inversions:
Under normal
conditions air
tends to rise and
mix with the air
above. Droplets Altitude
will disperse and
will usually not
cause problems.
Normal Temperature Profile
Cooler
Temperature decreases
with height
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.
Temperature Inversion
Temperature increases
with height
Altitude
Cool Air
Increasing Temperature
Warm Air
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’
Courtesy – George Ramsay, Dupont
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.
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.
Evaporation of Droplets:
High Relative Humidity
Low Temperature
Wind
Low Relative Humidity
High Temperature
Strategies to Reduce Drift:
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Select nozzle to increase drop size
Increase flow rates - higher application volumes
Use lower pressures
Use lower spray (boom) heights
Avoid high application speeds/rapid speed changes
Avoid adverse weather conditions
• High winds, light & variable winds, calm air
 Consider using buffer zones
 Consider using new technologies:
• drift reduction nozzles
• drift reduction additives
• shields, electrostatics, air-assist
Field Comparisons for Drift
Reducing/Deposition Aid
Tank Mixes
Materials and Methods:
 AT 502A (Hawkeye Flying Service)
•
•
•
•
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Drop booms
CP-09 nozzles w/5° deflection
Combination of .078 and .125 orifice settings
40 psi
150 mph ground speed by radar
•
•
•
•
•
Ag Tips
CP-03 w/30 degree deflection
Combination of .078 and .125 orifice settings
26 psi
115 mph ground speed by radar
 Cessna 188 Ag Husky (Rucker Flying Service)
 Aircraft calibrated for 3 GPA
Participants in the Study:
 United
Suppliers
 Helena Chemical
 Garrco
 Loveland
 Wilber-Ellis
 Rosen’s
 Precision Labs
 SanAg
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
41-A
Formula One
AMS 20/10
Border EG 250
Control
INT VWZ
Inplace
Garrco Exp-3
INT YAR
Border XTRA 8L
11. HM2005-C
12. HM0226
13. Liberate
14. Target LC
15. HM2052
16. INT HLA
17. HM 0230
18. Valid
19. Double Down
20 & 21. water
Collection Procedure for drift:
Final Rank – Horizontal @ 4.2 mph - AT
PRODUCT
C
INT HLA
P
GARCO #3
H
CONTROL
E
DOUBLE DOWN L
41-A
T
INT YAR
I
BORDER XTRA 8L
J
HM0226
B
LIBERATE
M
TARGET LC
N
TAP WATER
S
FORMULA ONE A
HM 0230
Q
INPLACE
G
INT VWX
F
BORDER EG 250D
VALID
R
HM 2052
O
HM 2005C
K
AMS 20/10
POINT TOTAL
PRODUCT / AT SUMMARY RATING
150
100
50
0
C P HE L T I J BMNS AQG F DR OK
PRODUCT
CODE
PT. TOT.
9
9
31
32
48
50
63
64
71
73
77
78
80
91
94
101
104
119
120
122
Final Rank – Horizontal @ 4.2 MPH - Cessna
PRODUCT
POINT VALUE
PRODUCT / CESSNA SUMMARY RATING
150
100
50
0
H E L P T F D S A R Q O J I CG MB N K
PRODUCT
CODE PT TOT
H
CONTROL
E
DOUBLE DOWN L
INT HLA
P
41-A
T
INT VWX
F
BORDER EG 250 D
TAP WATER
S
FORMULA ONE A
VALID
R
HM 0230
Q
HM 2052
O
BORDER XTRA J
INT YAR
I
AMS 20/10
C
INPLACE
G
LIBERATE
M
HM0226
B
TARGET LC
N
HM 2005C
K
GARCO #3
18
28
31
37
37
39
62
64
66
68
70
72
83
92
102
104
109
116
119
137
Final Rank – Vertical @ 4.2 MPH - AT
PRODUCT / AT SUMMARY RATING
PRODUCT
CODE
PT. TOT
AMS 20/10
C
T
P
L
A
H
N
B
G
J
E
I
M
F
S
K
D
Q
R
O
20
21
43
52
59
60
69
75
88
92
100
104
105
110
113
129
132
147
164
180
41-A
INT HLA
DOUBLE DOWN
200
FORMULA ONE
POINT VALUE
GARCO #3
150
TARGET LC
HM0226
INPLACE'
100
BORDER XTRA 8L
CONTROL
50
INT YAR
LIBERATE
INT VWX
0
TAP WATER
C T P L A H N B G J E I M F S K D Q R O
PRODUCT
HM2005C
BORDER EG 250
HM 0230
VALID
HM 2052
Final Rank – Vertical @ 4.2 MPH - Cessna
PRODUCT
PRODUCT / CESSNA SUMMARY RATING
DOUBLE DOWN
INT VWX
CONTROL
GARCO #3
200
POINT TOTAL
41-A
HM 0230
150
FORMULA ONE
VALID
INT HLA
100
HM 2052
TARGET LC
50
INPLACE
BORDER EG 250
LIBERATE
0
TAP WATER
L F E H T Q A R P O N G D M S I B J C K
PRODUCT
INT YAR
HM0226
BORDER XTRA 8L
AMS20/10
HM 2005C
CODE PT. TOT
L
F
E
H
T
Q
A
R
P
O
N
G
D
M
S
I
B
J
C
K
30
40
45
48
51
55
66
87
90
97
102
103
105
108
116
122
123
141
155
180
Documentation – Recordkeeping:
 All certified applicators are required to
maintain records of federally restricted
use pesticide (RUP) applications.
Pesticide Recordkeeping Requirements:
 Optional information ??????
•
•
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•
Target pest(s)
Size/density of pest
Adjuvants
Application method
 Aerial, ground, chemigation, incorporation
• Special equipment details
 Boom/nozzle, airplane, helicopter, banding
 Droplet size, pressure
• Reentry time/date
• Environmental conditions – Actual
 Wind speed, direction, temperature, humidity, time
Why am I keeping all of this information?
Refresh your memory
Safety
Better performance
Demonstrate care and concern
Stay ahead of the competition
Pesticide Recordkeeping Survey
Pesticide Education Program - Carol Ramsay and Carrie Foss
Washington State University
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At-Program Recordkeeping Survey – Jan.–March 2002
number of attendees = 2,191
sample size = 826
sample is 38% of attendees
 Post-Program Recordkeeping Survey – August 2002
 surveys mailed = 490
 sample size = 155
 response rate is 32% of mailed surveys
How do you measure wind speed?
do not measure
anemometer
local radio or tv station
weather web site
observe flag movement
on flag pole
local weather station
wind meter
best estimate
Carol Ramsay and Carrie Foss – Washington State University-2002
At Program Post Program
4%
5%
5%
6%
6%
4%
8%
4%
7%
13%
10%
16%
11%
15%
40%
34%
What measure do you use for wind speed?
Use words: calm, gusty, variable
 At Program
38%
 Post Program
33%
In miles per hour (or feet per second)
 At Program
62%
 Post Program
67%
Carol Ramsay and Carrie Foss – Washington State University-2002
How do you measure wind direction?
At Program Post Program
do not measure
4%
3%
compass
5%
3%
local radio or tv station
4%
6%
local weather station
6%
10%
dust and best estimate
9%
12%
flag or flagging tape
13%
14%
best estimate
44%
36%
Carol Ramsay and Carrie Foss – Washington State University-2002
What measure do you use for wind direction?
general direction (S, SSW, ESE, W)
At Program
94%
Post Program
97%
compass reading (172˚)
At Program
6%
Post Program
3%
Carol Ramsay and Carrie Foss – Washington State University-2002
How do you measure temperature?
At Program Post Program
do not measure
2%
2%
other
3%
5%
internet weather web site
5%
5%
best estimate
19%
8%
local weather station
18%
26%
thermometer/anemometer
53%
54%
Carol Ramsay and Carrie Foss – Washington State University-2002
In Conclusion:
Minimizing spray drift is in
the best interests of
everyone. Do your part to
keep applications on target.
Disclaimer:
Brand names appearing in this
presentation are for identification and
illustration purposes only.
No endorsement is intended, nor is
criticism implied of similar products not
mentioned.
For more information contact:
rewolf@ksu.edu
www.bae.ksu.edu/faculty/wolf/