Understanding Spray Drift

Technical Aspects of Spray Drift Why Interest in Drift? u Spotty pest control u Wasted chemicals u Off-target damage u More high value specialty crops u Less tolerant neighbors u Litigious Society u Result-higher costs-$$$ u More wind?? (Timing) u Environmental impact  Water and Air Quality u Public more aware of pesticides (Negative) (Perceptions) u Urban sprawl

Technical Aspects of Spray Drift The Drift: u Creating smaller spray drops will result in increased drift.

Technical Aspects of Spray Drift Nozzles are important: u Control the amount – GPA. u Determine uniformity of application. u Affects the coverage. u Influences the drift potential.

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  chemical  formulation  drop size  evaporation Equipment & Application  nozzle type  nozzle size  nozzle pressure  height of release Weather  air movement (direction and velocity)  temperature and humidity  air stability/inversions  topography

Technical Aspects of Spray Drift Wind Direction: u 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 u 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 u Because:  Light winds (0-3 mph) - unpredictable & variable in ALL directions.  Calm & low wind conditions? - temperature inversion u Drift potential is lowest at wind speeds between 3 and 10 mph (gentle but steady breeze) blowing in a safe direction. More drift at low Wind speeds?

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 NameFeaturesCost* DwyerFloating Ball15.50 Wind WizardMechanical39.50 Turbo MeterWind speed - knots, feet/min, meters/sec, mph Kestrel 1000Maximum, average, current wind speed - knots, feet/min, meters/sec, mph Kestrel 2000Maximum, average, current wind speed, temp, wind chill- knots, feet/min, meters/sec, mph Kestrel 3000All wind speed features plus temp, wind chill, dew point, heat index, relative humidity Plastimo Iris 50**Compass89.00 Wind Meters and Compass *Prices for Wind Meters taken from Gempler’s 2000 Master Catalog **Plastimo Airguide Inc., 1110 Lake Cook Road, Buffalo Grove, IL 60089( )

Technical Aspects of Spray Drift Air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems. Normal Temperature Profile Altitude Cooler Warmer Temperature decreases with height Increasing Temperature Inversions: Normal Conditions

Technical Aspects of Spray Drift Temperature increases as you move upward. Prevents air from mixing with the air above it. Small suspended droplets form a concentrated cloud Move in unpredictable directions. Temperature Inversion Altitude Temperature increases with height Warm Air Cool Air Increasing Temperature Temperature Inversions:

Technical Aspects of Spray Drift Recognizing Inversions:

Technical Aspects of Spray Drift Precautions for Inversions: u Surface inversions are common. u 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 u Use of a smoke bomb or smoke generator is recommended to identify inversion conditions.

Spray Droplet Size

Technical Aspects of Spray Drift One micron (  m ) =1/25,000 inch Relationship of Drift to Drop Size

Technical Aspects of Spray Drift Comparison of Micron Sizes for Various Items: (approximate values) u pencil lead 2000 (  m ) u paper clip 850 (  m ) u staple 420 (  m ) u toothbrush bristle 300 (  m ) u sewing thread150 (  m ) u human hair100 (  m ) 150

Technical Aspects of Spray Drift u Very Fine (VF) < 182µm u Fine (F) µm u Medium (M) µm u Coarse (C) µm u Very Coarse (VC) µm u Extremely Coarse (XC) >656µm *USDA ARS College Station, TX Droplet ClassDroplet Size Range

Technical Aspects of Spray Drift Efficacy and Drift Potential is Influenced by: u Size of the Spray Droplets - Volume Median Diameter (VMD) u Droplet Spectrum (Range - big to small) u Size of the Spray Droplets - Volume Median Diameter (VMD) u Droplet Spectrum (Range - big to small)

Technical Aspects of Spray Drift 1/2 of spray volume = larger droplets VMD 1/2 of spray volume = smaller droplets

Technical Aspects of Spray Drift Spray Droplet Movement with Various Wind Speeds

Technical Aspects of Spray Drift Evaporation of Droplets Wind High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance

Technical Aspects of Spray Drift Nozzle Technology? u Nozzles designed to reduce drift u Improved drop size control u 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 40, 80 PSI Turbodrop 40, 80 PSI Boom Drift

Technical Aspects of Spray Drift Strategies to Reduce Drift: u Select nozzle to increase drop size u Increase flow rates - higher application volumes u Use lower pressures u Use lower spray (boom) heights u Avoid adverse weather conditions u Consider using buffer zones u 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:  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 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