Understanding Spray Drift Reeves Petroff Pesticide Education Specialist Montana State University Extension

Technical Aspects of Spray Drift

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

Technical Aspects of Spray Drift u Guidance to Chemical Manufacturers u Matching the pesticide to the target u More exacting label guidelines u Buffer Zones or No Spray Zones u Maximize Efficacy u Minimize Drift EPA Requested Changes Coming !?!?

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  evaporation  drop size 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  Location of sensitive areas  Consider buffer zones.  If it is blowing towards sensitive areas – STOP  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) u unpredictable & variable in direction.  Calm & low wind conditions? - temperature inversion u Drift potential is lowest  3 and 10 mph  gentle but steady breeze  blowing in a safe direction. What ‘n’ Why?

Technical Aspects of Spray Drift Wind Current Effects u Wind currents can affect spray droplet deposition u Structures 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 rises Mixes with air above. Droplets will disperse Usually no problems. Normal Temperature Profile Altitude Cooler Warmer Temperature decreases with height Increasing Temperature Normal Conditions

Technical Aspects of Spray Drift Temperature increases with altitude. Prevents air from mixing with the air above it. Small suspended drops form a concentrated cloud Moves in unpredictable directions. Temperature Inversion Altitude Warm Air Cool Air Increasing Temperature Temperature Inversions:

Technical Aspects of Spray Drift Recognizing Inversions: u Clear to partly cloudy skies u Light winds u Inversion can form as the sun sets. u Continues into the morning until the sun begins to heat the ground.

Technical Aspects of Spray Drift Precautions for Inversions: u Surface inversions are common. u Be careful near sunset and an hour or so after sunrise, unless…  Low heavy cloud cover  Wind speed > 5-6 mph  5 o temp rise after sun-up u Observe smoke or dust to identify inversion conditions.

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 Nozzles & drift: u Creating smaller spray drops will result in increased drift.  Nozzle tip  Weather

Spray Droplet Size

Technical Aspects of Spray Drift Size Matters! All nozzles produce a wide range of droplet sizes Big to small All nozzles produce a wide range of droplet sizes Big to small

Technical Aspects of Spray Drift One micron ( um ) =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 ASAE DSC and Volume Median Diameter (D V0.5 ) From PMS* Laser Spectrometer 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 Spectra Classification (DSC) Droplet Size Range

Technical Aspects of Spray Drift Is Drift Bad? Are all small droplets bad?

Technical Aspects of Spray Drift Nozzle Drop Size Classes Very Fine to Fine < 200 um Medium to Coarse 200 to 450 um Very Coarse > 450 um

Technical Aspects of Spray Drift

80 means 80 o fan 03 = 0.3 GPM at 40 psi (38 ½ ounces per minute) 8003 tip

Technical Aspects of Spray Drift Tip Spray Selection by Drop Size Turbo TeeJet Flat-fan

Technical Aspects of Spray Drift Spray Characteristics are Important to Understand: Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind

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

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 Evaporation of Droplets Wind High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance 200 um 100 um

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 80 PSI Turbodrop – A.I. Boom Small Drops 40 PSI20 PSI XR Flat-fan 80 PSI40 PSI20 PSI

Technical Aspects of Spray Drift Strategies to Reduce Drift: Match nozzle to target pest  Larger application volumes - GPA  Use lower pressures  Use lower spray (boom) heights Weather? 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:  Scheduling and planning the application  Obtaining the products  Setting up the application date  Weather delays or maintenance problems, if necessary. “I need to spray RIGHT NOW!”. Don’t Force A Job

Technical Aspects of Spray Drift Applicator Nozzle

Technical Aspects of Spray Drift T hanks