Understanding Spray Drift

1. Understanding Spray Drift

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

3. The Drift: • Creating smaller spray drops will result in increased drift.

4. Nozzles are important: • Control the amount – GPA. • Determine uniformity of application. • Affects the coverage. • Influences the drift potential.

5. Definition of Drift: Movement of spray particlesand vaporsoff-target causing less effective control and possible injury to susceptible vegetation, wildlife, and people.

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

7. 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

8. 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.

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

10. Wind Current Effects Structures drastically affect wind currents • Wind breaks • Tree lines and orchards • Houses and barns • Hills and valleys

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

12. 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)

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

14. Temperature Inversion Warm Air Temperature increases with height Altitude Cool Air Increasing Temperature Temperature Inversions: 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.

15. Recognizing Inversions:

16. Spray Droplet Size

17. Relationship of Drift to Drop Size One micron (m) =1/25,000 inch

18. 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

19. Droplet Class Droplet Size Range • Very Fine (VF) < 182µm • Fine (F) 183-280µm • Medium (M) 281-429µm • Coarse (C) 430-531µm • Very Coarse (VC) 532-655µm • Extremely Coarse (XC) >656µm *USDA ARS College Station, TX

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

21. 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

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

23. Nozzle Technology? • Nozzles designed to reduce drift • Improved drop size control • Emphasis on ‘Spray Quality’

24. Spray Characteristics are Important to Understand: Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind

25. 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, electrostatics, air-assist

26. 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.

27. Thank You