Understanding Spray Drift

1. Understanding Spray Drift Robert E. Wolf Extension Specialist Application Technology Biological and Agricultural Engineering

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

3. Productivity The application triangle Off-site protection Efficacy

4. Technical Aspects of Spray Drift

5. 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

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. 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.

10. Spray Droplet Movement with Various Wind Speeds

11. 30 20 10 6 2 0 11 mph 10 mph 8 mph Height Above Crop Canopy, Feet 7 mph 5 mph Wind Speeds Gradients Wind Speed The relation between height above the canopy of a crop like cotton or soybean and the speed of wind.

12. Wind Current Effects • Wind currents can drastically affect spray droplet deposition • Structures drastically affect wind currents • Wind breaks • Tree lines and orchards • Houses and barns • Hills and valleys

13. 3 2 Height 5 0 5 10 15 Wind Patterns Near Shelterbelts Distance from shelterbelt (tree heights) Generalized pattern of wind in the neighborhood of a shelterbelt.

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

15. 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)

16. 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 2002 Master Catalog **Plastimo Airguide Inc., 1110 Lake Cook Road, Buffalo Grove, IL 60089(708-215-7888)

17. 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.

18. 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.

19. 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.

20. Courtesy – George Ramsay, Dupont

21. 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.

22. Spray Droplet Size

23. Efficacy and Drift Potential is Influenced by • Size of the Spray Droplets - Volume Median Diameter (VMD) • Droplet Spectrum (Range - big to small) % Volume in droplets less than 200 microns in size

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

25. 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

26. 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets

27. 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

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

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

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

31. ASAE S-572 Droplet Size Standard

32. Coverage • Need knowledge of the product being used. • Systemic • Contact • What is the target? • Soil • Grass • Broadleaf (smooth, hairy, waxy) • Leaf orientation – time of day

33. ASAE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer Droplet Spectra Classification (DSC) 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

35. Computer Models:

36. AgDRIFT® Program Map

37. Example of Model Use – Aerial Applicators Standard Operation

38. 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 high application speeds/rapid speed changes • Avoid adverse weather conditions • High winds, light & variable winds, calm air • Consider using buffer zones • Consider using new technologies: • drift reduction nozzles • drift reduction additives • shields, electrostatics, air-assist

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

40. Goodland Drift Project • 8 Companies • 19 Drift Reduction/Deposition Aids • Water • X-77 @ .25% • 2 Airplanes • AT 502 - Hawkeye – Bill and Dave • Cessna Ag Husky w/wing tips – Cary • 3 reps with the drift tower • 1 pass over a canopy – top and bottom • 260 flight passes each • 4600 cards

41. 41-A Formula One AMS 20/10 Border EG 250 Control INT VWZ Inplace Garco Exp-3 INT YAR Border XTRA 8L HM2005-C HM0226 Liberate Target LC HM2052 INT HLA HM 0230 Valid Double Down Participants in the Study: Companies Products • United Suppliers • Helena Chemical • Garco • Loveland • Wilber-Ellis • Rosen’s • Precison Labs • SanAg

42. 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.

43. In Conclusion Minimizing spray drift is in the best interests of everyone. Do your part to keep applications on target.

44. Thank You

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