Transcript Drift
Understanding Spray Drift Why Interest in Drift? Wasted chemicals Off-target damage Less tolerant neighbors Litigious Society Environmental impact Water and Air Quality Public more aware of pesticides (Negative) (Perceptions) Urban sprawl Technical Aspects of Spray Drift Nozzle Technology? Nozzles designed to reduce drift Improved drop size control Emphasis on ‘Spray Quality’ Technical Aspects of Spray Drift Nozzles are important: the amount – GPA. Determine uniformity of application. Affects the coverage. Influences the drift potential. Control Technical Aspects of Spray Drift Nozzles & drift: Creating smaller spray drops will result in increased drift. Technical Aspects of Spray Drift 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 drop size evaporation Weather air Equipment & Application nozzle type nozzle size nozzle pressure height of release movement (direction and velocity) temperature and humidity air stability/inversions topography Technical Aspects of Spray Drift Wind Direction: Wind direction is very important Location of sensitive areas? buffer zones. Do not spray if blowing towards sensitive areas 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 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 & 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. Technical Aspects of Spray Drift 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 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 Wind Meters and Compass 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 *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) Technical Aspects of Spray Drift Inversions: Under normal conditions air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems. Technical Aspects of Spray Drift Normal Temperature Profile Cooler Temperature decreases with height Altitude Warmer 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. Technical Aspects of Spray Drift Temperature Inversion Temperature increases with height Altitude Cool Air Increasing Temperature Warm Air Recognizing Inversions: Under clear to partly cloudy skies and light winds, a surface inversion can form as the sun sets. Surface inversion will continue into the morning until the sun begins to heat the ground. Technical Aspects of Spray Drift 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. Technical Aspects of Spray Drift Spray Droplet Size 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 Technical Aspects of Spray Drift Relationship of Drift to Drop Size One micron (m) =1/25,000 inch Technical Aspects of Spray Drift Comparison of Micron Sizes for Various Items: (approximate values) pencil lead 2000 (m) paper clip 850 (m) 150 toothbrush bristle sewing thread 420 (m) 300 (m) 150 (m) human 100 (m) staple hair Technical Aspects of Spray Drift Spray Droplet Movement with Various Wind Speeds Droplet Sizes (microns) 5 mph Wind 10 mph Wind 15 mph Wind 20 mph Wind 100 24 ft. 48 ft. 72 ft. 96 ft. 200 9 18 26 35 400 5 9 14 18 500 4 7 10 14 600 3 6 9 12 Boom height: 3 feet Technical Aspects of Spray Drift 1/2 of spray volume = smaller droplets VMD 1/2 of spray volume = larger droplets Technical Aspects of Spray Drift Evaporation of Droplets High Relative Humidity Low Temperature Wind Technical Aspects of Spray Drift Low Relative Humidity High Temperature Spray Characteristics are Important to Understand: Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind Technical Aspects of Spray Drift XR Flat-fan @20, 40, 80 PSI Boom Drift Technical Aspects of Spray Drift Turbodrop XL @20, 40, 80 PSI ASAE DSC and Volume Median Diameter (DV0.5) From PMS* Laser Spectrometer Droplet Spectra Classification (DSC) Very Fine (VF) Fine (F) Medium (M) Coarse (C) Very Coarse (VC) Extremely Coarse (XC) Droplet Size Range < 182µm 183-280µm 281-429µm 430-531µm 532-655µm >656µm *USDA ARS College Station, TX Technical Aspects of Spray Drift 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 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. 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. Technical Aspects of Spray Drift In Conclusion: Minimizing spray drift is in the best interests of everyone. Do your part to keep agrichemical applications on target. Technical Aspects of Spray Drift Technical Aspects of Spray Drift