Understanding Spray Drift

1. Understanding Spray Drift Robert E. Wolf Extension Specialist Application Technology

2. Why Interest in Drift? • Spotty pest control • Wasted chemicals • Off-target damage • Litigious Society ???? • Result - higher costs - $$$ • Windy?? (Timing) • Environmental impact (Water and Air Quality)

3. Misapplication Facts:

4. Facts about drift:

5. Why is the Nozzle Important? • Amount of spray applied • Uniformity of the spray • Coverage on the target • Amount of off-target drift

6. Technical Aspects of Spray Drift

7. Definition of Drift: Movement of spray particlesand vaporsoff-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

8. Types of Drift: Vapor Drift - associated with volatilization (gas, fumes) Particle Drift - movement of spray particles during or after the spray application

9. Factors Affecting Drift: • Equipment & Application • nozzle type • nozzle size • nozzle pressure • height of release • Weather • air movement (direction and velocity) • temperature and humidity • air stability/inversions • topography Spray Characteristics • chemical • formulation • drop size • evaporation

10. 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 arenever recommended.

11. 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 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(708-215-7888)

12. Normal Temperature Profile Cooler Temperature decreases with height Altitude Warmer Increasing Temperature Inversions: Under normal conditions air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems.

13. Temperature Inversion Warm Air Temperature increases with height Altitude Cool Air 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.

14. 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.

16. 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.

17. Wind Patterns Near Treelines: Adapted from Survey of Climatology: Griffiths and Driscoll, Texas A&M University, 1982

18. 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)

19. Spray Droplet Size

20. Drift & Dropsize Relationship: • Particle drift will result from the smaller drops created during the spray process. The size of the droplets created is critical. • Dropsizes are measured in microns using laser beams.

21. Dropsize Facts: • One micron = 1/25,000 inch • Expressed as (VMD) Volume Median Diameter • Example - VMD = 500 microns

22. pencil lead 2000 (m) paper clip 850 (m) staple 420 (m) toothbrush bristle 300 (m) sewing thread 150 (m) human hair 100 (m) Comparison of Micron Sizes for Various Items: (approximate values) 150

23. Raindrop compared to a Turbo Turf Flood 5.0 MPH wind at 40 psi Turbo Turf Flood Raindrop Drop

24. 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

25. Cutting Droplet Size in HalfResults in Eight Times the Number of Droplets 250 Microns 250 Microns 500 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns

26. Important Droplet Statistics: VMD (50%) VD0.9 (90%) Operational Area VD0.1 (10%)

27. Evaporation of Droplets High Relative Humidity Low Temperature Low Relative Humidity High Temperature Fall Distance Wind

28. 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

29. Drift Reduction Additives: • Many available! • Not EPA regulated • Long chain polymers • New-soluble powders • 50 - 80% reduction in off-target movement • Pump shear problems

31. New Label language-EPA 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 Example Reference Graph 900 800 very fine/ fine fine/medium medium/ coarse coarse/ very coarse 700 very coarse/ extremely coarse 600 XC 500 C VC 400 M 300 F 200 Drop Size (microns) VF 100 0 0.1 0.5 0.9 Cumulative Volume Fraction EPA Requested Changes Coming!!!! VMD

33. For more information contact: rewolf@ksu.edu www.bae.ksu.edu/rewolf/