Transcript No Slide Title

Herbicide Drift Management
John Boyd
University of Arkansas
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What is drift?
Movement of
spray particles
and/or vapors offtarget.
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Types of Drift


Vapor Drift - associated with
volatilization, gases and fumes.
Particle Drift - movement of spray
particles.
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Misapplication Facts
2%
8%
33%
24%
33%
Equipment
Drift
Tank Mix
Wrong Field
Off Label
Source: Farmland Insurance 1996
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Contributions to Drift
13%
23%
26%
Nozzle
Applicator
Physical
Other
38%
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Factors Affecting Drift
Spray Characteristics Equipment &
Application
Herbicide
Nozzle type
Formulation
Nozzle size
Additives
Nozzle orientation
Drop size
Nozzle pressure
Evaporation
Height of release
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Weather & other Factors
Affecting Drift




Temperature & humidity
Wind (direction and velocity)
Air stability/inversions
Topography
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Drift Potential Depends on



The percentage of small droplets in the
droplet size range.
Droplet size is measured in microns.
The key factor is the percentage of the
spray droplets less than 200 microns in
diameter.
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Droplet Size


Spray drift droplets are
measured in microns and
expressed as Volume Median
Diameter or VMD
One micron = 1/25,000th inch
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Comparison of Micron Sizes
100 microns
Human hair
150 microns
Sewing thread
300 microns
Toothbrush bristle
420 microns
Staple
850 microns
Paper clip
2000 microns
#2 Pencil lead
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1/2 of spray volume = smaller droplets
VMD
1/2 of spray volume = larger droplets
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Results in Eight Times the
Cutting
Droplet Size in Number of Droplets
Half
500
Microns
=
250
Microns
2 more
droplets fill in
the sphere
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Important Droplet Statistics:
Operational
Area
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Evaporation and Deceleration of Various
Size Droplets*
Droplet
Diameter
(microns)
Terminal
Velocity
(ft/sec)
Final Drop Time to
diameter evaporate
(microns)
(sec)
Deceleration
distance
(in)
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.04
7
0.3
<1
50
.25
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1.8
3
100
.91
33
7
9
150
1.7
50
16
16
200
2.4
67
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*Conditions assumed: 90 F, 36% R.H., 25 psi., 3.75% pesticide solution
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Nozzle Drop Size
Classification
British Crop Protection Council (BCPC)
Size
Very
Fine
Fine
Dv0.1 <55*
55-94
Dv0.5 <119
Medium Coarse
95-164
Very
Coarse
165-225
>225
119-216
217-353 354-464
>464
Dv0.9 <204 204-369
370-598 599-789
>789
%<141 57.2 20.2-57.2 5.7-20.1
2.9-5.6
<2.9
*Numbers listed are in Microns
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Drop Size Classification & Use



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
Very Fine
Fine
Medium
Coarse
Very
Coarse
 <119 m
 119-216
m
 217-353
m
 354-464
m
 >464 m
Insecticides
and Fungicides
Herbicides and
Postemergence
Soil Applications
of Herbicides
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Software for estimating droplet size distribution is
available on the web.
http://apmru.usda.gov/downloads/downloads.htm
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Evaporation of Droplets
High Relative Humidity
Low Temperature
Low Relative Humidity
High Temperature
Wind
Wind
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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.
Spraying in dead calm conditions is never
recommended.
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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.
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Conditions

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Where are what are the adjacent
crops?
Are there houses, a town or other
sensitive areas near the site?
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Buffer Zone

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A buffer zone means an area where
pesticide is not directly applied thereby
providing protection to a defined area.
Buffer zones may depend on:

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state regulations
pesticide product labels
prevailing weather conditions
sensitive/protected area(s)
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Product Selection



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You may have several options on
products.
Understand the product chemistry!
Consider the effect this product may
have on homes and gardens near the
application site.
Consider environmental and wildlife
safety.
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Equipment Selection and Setup


Select equipment to produce the largest
droplet size possible and still provide
adequate coverage.
Be aware that some products require
relatively smaller droplets to ensure
good coverage.
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When Planning a Spray
Application


Allow enough time for planning and
executing the operation. Including
weather and equipment delays.
Do not 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.
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Wind Direction

Wind direction is very important

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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.
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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.
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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)
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Recognizing Inversions:

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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.
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Precautions for Inversions

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Surface inversions are common .
Be especially 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
Use of a smoke bomb or smoke
generator is recommended to
identify inversion conditions.
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Nozzles are important
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Control the amount – GPA.
Determine uniformity of application.
Affects the coverage.
Influences the drift potential.
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Spray Characteristics are Important to Understand
Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind
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XR Flat-fan @20, 40, 80 PSI
Turbodrop XL @20, 40, 80 PSI
Boom
Drift
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Strategies to Reduce Drift
 Increased drop size.
 Higher application volumes.
 Lower pressure.
 Avoid adverse weather conditions.
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Strategies to Reduce Drift
 Buffer zones.
 Drift reduction nozzles
 Drift reduction additives

Consider using new technologies:
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drift reduction nozzles
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