9/30/ Managing Pesticide Drift. Which size droplet? Robert E. Wolf. Spray Droplet Management - Coverage

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1 Managing Pesticide Drift For more information contact: Adapted from a presentation by Robert E. Wolf Extension Specialist Application Technology Biological and Agricultural Engineering Which size droplet? Productivity Spray Droplet Management - Coverage The application triangle Efficacy Courtesy of Ken Giles, U of California Davis Off-site protection Need knowledge of the product being used. Herbicide, Fungicide, Insecticide Systemic Contact What is the target? Soil Grass Broadleaf (smooth, hairy, waxy) Leaf orientation time of day Penetration into canopy 9/30/2016 1

2 Why Interest in Drift? Technical Aspects of Spray Drift Spotty pest control Wasted chemicals Off-target damage More high value specialty crops Urban sprawl and... Less tolerant neighbors Litigious Society Environmental impact Water and Air Quality Public more aware of pesticide concerns! (Negative Perceptions) Result-higher costs-$$$ 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 Types of Drift: Vapor Drift - associated with volatilization (gas, fumes) Particle Drift - movement of spray particles during or after the spray application Vapor drift 2,4-D Dicamba 9/30/2016 2

3 Vapor Drift Pesticide forms a vapor which drifts offsite pesticide dependent Vapor pressure - the ability of a chemical to form a vapor. 2,4-D ester =.0017 mmhg Dicamba = mmhg Glyphosate = mmhg 2,4-D salt = mmhg Volatility is affected by weather High temperatures 2,4-D ester is twice as volatile at 80 0 vs 70 0 F Low humidity increases volatility Air inversions Factors Affecting Particle Drift: Efficacy and Drift Mitigation: Spray Characteristics chemical formulation droplet size evaporation & humidity Weather Equipment & Application nozzle type nozzle orientation nozzle pressure height of release air movement (direction and velocity) temperature and humidity air stability/inversions topography Size of the Spray Droplets - Microns Volume Median Diameter (VMD) Droplet Spectrum (Range - big to small) % Volume in droplets less than 200 microns in size Drop Size microns (µm) Comparison of Micron Sizes for Various Items: (approximate values) One micron (µm) =1/25,000 inch One millionth of a meter pencil lead paper clip 50 staple toothbrush bristle sewing thread human hair 2000 (µm) 850 (µm) 420 (µm) 300 (µm) 150 (µm) 100 (µm) 9/30/2016 3

4 1/2 of spray volume = smaller droplets Important Droplet Statistics: VMD Operational Area 1/2 of spray volume = larger droplets VMD greater than or equal to 200 Pressure and nozzles More drift High Pressure Higher spray height Wide spray angle nozzle Low flow rate (small orifice) Less drift Lower pressure Low height Narrow angle Higher flow rate Nozzles and Droplets - cals.arizona.edu Nozzles Types? Tunnel Drift Results: Coverage on WSP at 1 Meter Downw ind 9/30/ Percent Area Coverage LSD = 12.7 tr8004 tr xr800 4 mci1.875 xr tkvs2 dg tt11004 ra4 tfvp2 tfvs2 ab11004 dr80-04 am rf4 avi ai11004 td04-xr11008 ru-4cp td04-tt uld ttj04

5 Air-Assist Sprayers: Where a curtain of high speed air is used to assist with particle movement after leaving the nozzle. Air Assist Spraying: Process using air energy to aid in the atomization, transportation, penetration, deposition of spray products. Potential for reduced rates of carrier & ai Best for dense plant canopies not bare ground! Electrostatic Spraying Turbulence, preorifice chambers Spray Coupe with ESP Air induction nozzles Introduces air to spray mix Creates bubbles Reduces number of small droplets and drift 9/30/2016 5

6 Weather & drift air movement (direction and velocity) Topography, etc. temperature and humidity air stability/inversions Courtesy George Ramsay, Dupont direction: direction 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. (3-10 mph) Dead calm conditions are never recommended. Determining wind direction: Drift Potential: High at Low Speeds? Compass Provide magnetic description Direction blowing from Into your face! Avoid dead calm 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. Speeds: Spray Droplet Movement mph 10 mph Droplet Sizes (microns) 5 mph 10 mph 15 mph 20 mph ft. 48 ft. 72 ft. 96 ft Height Above Crop Canopy, Feet mph 7 mph 5 mph Boom height: 3 feet The relation between height above the canopy of a crop like cotton or soybean and the speed of wind. 9/30/2016 6

7 Current Effects: currents can drastically affect spray droplet deposition Structures drastically affect wind currents breaks, hills, valleys Buildings Patterns Near Treelines: Adapted from Survey of Climatology: Griffiths and Driscoll, Texas A&M University, 1982 Patterns Around Buildings: Handheld windmeters: Ground Diagram of wind around a building. Adapted from Farm Structures* * H.J. Barre and L.L. Sammet, Farm Structures (Wiley, 1959) On board weather instrumentation: Inversions: Under normal conditions air tends to rise and mix with the air above. Droplets will disperse and will usually not cause problems. Altitude Normal Temperature Profile Cooler Increasing Temperature Temperature decreases with height Warmer 9/30/2016 7

8 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. Altitude Temperature Inversion Temperature increases with height Cool Air Increasing Temperature Warm Air Cloud of 5-25 u oil droplets generated under unstable conditions 105 foot temperature monitoring tower F F F F 8 41 F Courtesy George Ramsay, Dupont Predicting 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. 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. Evaporation of Droplets: High Relative Humidity Low Temperature Low Relative Humidity High Temperature Drift Reduction Additives: Many available! Not EPA regulated Up to 50-80% reduction in offtarget movement Will all work? Effect on the pattern? Recalibration? content.ces.ncsu.edu/glyphosate 9/30/2016 8

9 EPA s Emphasis with Spray Drift Reduction Relationship Between Application Technologies, Amount of Drift/Risk, and Risk Management Drift Reduction Technology Program DRT Encourage the adoption of technology designed to reduce drift. Examples: Spray nozzles reduce fines Sprayer modifiers shields, hoods Spray delivery assistance air-assist Spray additives formulations, drift control Landscape modifications hedges, shelterbelts, buffer zones Better label information Match products to target Amount. of drift and risk No DRT DRT* DRT** DRT *** Level of concern for a pesticide for people, animals, plants Distance from application site Reducing Drift - a systems approach Select nozzle to increase droplet size Increase flow rates - higher application volumes Use lower pressures & spray (boom) heights Avoid inversions & very still conditions Spray with 3-10 mph breeze towards safe area Consider using buffer zones New technologies: drift reduction nozzles drift reduction additives Shields, hoods Disclaimer: Brand names appearing in this presentation are for identification and illustration purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Some info taken from SlidePlayer and the National Pesticide Info Center 9/30/2016 9