Understanding Spray Drift Reeves Petroff Pesticide Education Specialist Montana State University Extension http://mtpesticides.org Why Interest in Drift? Spotty pest control Wasted chemicals Result-higher costs-$$$ Off-target damage High value.
Download ReportTranscript Understanding Spray Drift Reeves Petroff Pesticide Education Specialist Montana State University Extension http://mtpesticides.org Why Interest in Drift? Spotty pest control Wasted chemicals Result-higher costs-$$$ Off-target damage High value.
Understanding Spray Drift Reeves Petroff Pesticide Education Specialist Montana State University Extension http://mtpesticides.org Why Interest in Drift? Spotty pest control Wasted chemicals Result-higher costs-$$$ Off-target damage High value specialty crops Less tolerant neighbors Urban sprawl Litigious Society Environmental impact Water and Air Quality Public more aware of pesticides (Negative) (Perceptions) Technical Aspects of Spray Drift EPA Requested Changes Coming !?!? Guidance to Chemical Manufacturers Matching the pesticide to the target More exacting label guidelines Buffer Zones or No Spray Zones Maximize Efficacy Minimize 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 evaporation drop size 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 Know the location of sensitive areas consider safe buffer zones. If it is blowing towards sensitive areas – STOP - 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 What ‘n’ Why? Because: Light winds (0-3 mph) tend to be unpredictable and variable in direction. Calm & low wind conditions? - temperature inversion Drift potential is lowest 3 and 10 mph gentle but steady breeze blowing in a safe direction. Technical Aspects of Spray Drift Wind Current Effects Wind currents can affect spray droplet deposition Structures 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 Normal Conditions • Air rises • Mixes with air above. • Droplets will disperse • Usually no problems. Normal Temperature Profile Cooler Temperature decreases with height Altitude Warmer Increasing Temperature Technical Aspects of Spray Drift Temperature Inversions: • Temperature increases with altitude. • Prevents air from mixing with the air above it. • Small suspended drops form a concentrated cloud • Moves in unpredictable directions. Temperature Inversion Temperature increases with height Altitude Cool Air Increasing Temperature Technical Aspects of Spray Drift Warm Air 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. Technical Aspects of Spray Drift Precautions for Inversions: Surface inversions are common . Be 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 Observe smoke or dust to identify inversion conditions. 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 Spray Droplet Size Size Matters! • All nozzles produce a wide range of droplet sizes • Big to small 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 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 Nozzle Drop Size Classes Very Fine to Fine < 200 um Medium to Coarse – 200 to 450 um Very Coarse > 450 um Technical Aspects of Spray Drift Technical Aspects of Spray Drift 8003 tip 80 means 80o fan 03 means 0.3 gallons per minute at 40 psi (38 ½ ounces per minute) Technical Aspects of Spray Drift Tip Spray Selection by Drop Size Turbo TeeJet Flat-fan 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 Evaporation of Droplets High Relative Humidity Low Temperature Wind Technical Aspects of Spray Drift Low Relative Humidity High Temperature Nozzle Technology? Nozzles designed to reduce drift Improved drop size control Emphasis on ‘Spray Quality’ Technical Aspects of Spray Drift 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 Strategies to Reduce Drift: Match nozzle to target pest 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 13% 23% 26% 38% Applicator Technical Aspects of Spray Drift Nozzle Nozzle Applicator Physical Other Thanks Technical Aspects of Spray Drift