2. Technical Aspects of Spray Drift Reeves Petroff Montana State University Extension Pesticide EDUCATION Specialist

3. Technical Aspects of Spray Drift Changes in the Application Industry! u Inefficient u Easy to make mistakes u Rates are changing (< an ounce/acre) u More pest specific products (foliar) u Biotechnology and GMO’s – Issues???? u More sophisticated equipment (electronics) $$$ u Variable rates u Site-specific u Focus on Drift

4. Technical Aspects of Spray Drift Why Interest in Drift? u Spotty pest control u Wasted chemicals u Off-target damage u Litigious Society u Result-higher costs-$$$ u More wind?? (Timing) u Environmental impact 4 Water and Air Quality u Public more aware of pesticide concerns! (Negative) u Spraying in more populated areas? (Suburbs)

5. Technical Aspects of Spray Drift Big lies u The check is in the mail. u I love you. u There’s no wind on the drop zone. u Always use the biggest drop possible. u Its best to spray when there’s no wind u Increase pressure to increase GPA

6. Technical Aspects of Spray Drift Nozzle Technology? u Nozzles designed to reduce drift u Improved drop size control u Emphasis on ‘Spray Quality’

7. 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.

8. Technical Aspects of Spray Drift Will affect drift: u Movement of spray particles off-target. u Creating smaller spray drops will result in increased drift. u Large droplets maybe result in bounce. $64,000 Question?

9. Technical Aspects of Spray Drift

10. 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

11. 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

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

13. Technical Aspects of Spray Drift Wind Direction: u Wind direction is very important 4 Know the location of sensitive areas – consider.. 4 Do not spray at any wind speed if it is blowing towards sensitive areas… 4 Spray when breeze is gentle, steady, and blowing AWAY from sensitive areas. 4 “Dead calm” conditions are recommended. safe buffer zones. ---all nozzles can drift--- NEVER

14. Technical Aspects of Spray Drift u Because: 4 Light winds (0-3 mph) tend to be unpredictable and variable in direction. 4 Calm and low wind conditions may indicate presence of a temperature inversion. u Drift potential is lowest at wind speeds between 3 and 10 mph (gentle but steady breeze) blowing in a safe direction. However, Drift Potential May be High at Low Wind Speeds

15. Spray Droplet Size

16. Technical Aspects of Spray Drift Drift 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) % Volume in droplets less than 200 microns in size % Volume in droplets less than 200 microns in size

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

18. 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

19. 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

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

21. Technical Aspects of Spray Drift Important Droplet Statistics: Operational Area

22. Technical Aspects of Spray Drift Cutting Droplet Size in Half Results in Eight Times the Number of Droplets 500 Microns 500 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns 250 Microns

23. Technical Aspects of Spray Drift Cutting Droplet Size in Half Results in Eight Times the Number of Droplets = = 2 more droplets fill in the sphere 500 Microns 500 Microns 250 Microns

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

25. Technical Aspects of Spray Drift Wind Speeds Gradients The relation between height above the canopy of a crop and the speed of wind. 30 20 10 6 2 0 11 mph 10 mph 8 mph 7 mph 5 mph Height Above Crop Canopy, Feet Wind Speed

26. Technical Aspects of Spray Drift Wind Current Effects u Wind currents can drastically affect spray droplet deposition u Structures drastically affect wind currents 4 Wind breaks 4 Tree lines and orchards 4 Houses and barns 4 Hills and valleys

27. Technical Aspects of Spray Drift Wind Patterns Near Shelterbelts Distance from shelterbelt (tree heights) Generalized pattern of wind in the neighborhood of a shelterbelt. 5 0 51015 32 32 Height

28. Technical Aspects of Spray Drift Wind Patterns Near Treelines Adapted from Survey of Climatology: Griffiths and Driscoll, Texas A&M University, 1982

29. Technical Aspects of Spray Drift Wind Patterns Around Buildings Diagram of wind around a building. Adapted from Farm Structures* Ground * H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)

30. Technical Aspects of Spray Drift Wind Patterns Around Buildings Diagram of Wind Around a Building Adapted From Farm Structures* Overhead View Wind * H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959)

31. Technical Aspects of Spray Drift NameFeaturesCost* DwyerFloating Ball15.50 Wind WizardMechanical39.50 Turbo MeterWind speed - knots, feet/min, meters/sec, mph135.00 Kestrel 1000Maximum, average, current wind speed - knots, feet/min, meters/sec, mph 89.00 Kestrel 2000Maximum, average, current wind speed, temp, wind chill- knots, feet/min, meters/sec, mph 119.00 Kestrel 3000All wind speed features plus temp, wind chill, dew point, heat index, relative humidity 159.00 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(708-215-7888)

32. Technical Aspects of Spray Drift Under normal conditions air rises and mixes 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:

33. Technical Aspects of Spray Drift Temperature increases with altitude. 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. Temperature Inversion Altitude Temperature increases with height Warm Air Cool Air Increasing Temperature Temperature Inversions:

34. Technical Aspects of Spray Drift Recognizing Inversions: u Under clear to partly cloudy skies and light winds, a surface inversion can form as the sun sets. u Under these conditions, a surface inversion will continue into the morning until the sun begins to heat the ground.

35. 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… 4 There is low heavy cloud cover 4 The wind speed is greater than 5-6 mph at ground level 4 5 degree temp rise after sun-up u Notice smoke or dust patterns to identify inversion conditions.

36. Technical Aspects of Spray Drift Evaporation and Deceleration of Various Size Droplets* *Conditions assumed: 90 F, 36% R.H., 25 psi., 3.75% pesticide solution

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

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

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

40. Technical Aspects of Spray Drift XR Flat-fan @ 20, 40, & 80 psi Turbodrop XL @ 20, 40, & 80 psi

41. Technical Aspects of Spray Drift

42. 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: 4 drift reduction nozzles 4 drift reduction additives 4 shields, electrostatics, air-assist

43. Technical Aspects of Spray Drift Some Other Things to Keep in Mind when Planning a Spray Application Allow enough time for: 4 Scheduling and planning the application 4 Obtaining the products 4 Setting up the application date 4 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.

44. Technical Aspects of Spray Drift In Conclusion: Minimizing spray drift is in the best interests of everyone. Do your part to keep pesticides on target.

45. Technical Aspects of Spray Drift s