WSDA Committee for Eastern Washington Herbicide Rules • Herbicides affected • 2,4-D MCPA, MCPP, and dicamba containing products • Walla Walla, Franklin, and Benton Counties herbicides also include • Sulfonylurea herbicides (SU’s), bromoxynil, glyphosate, dessicants & defoliants and Category 1 Insecticides
WSDA Committee for Eastern Washington Herbicide Rules • Fall 2008 – committee met • WSDA revising language in rule • Considering using droplet size performance standard versus existing equipment set-up stipulations • NEW: Use minimum of Medium (or Coarse) spray droplet • OLD: nozzle orifice, pressure, gallonage stipulated in rule
WSDA Herbicide Rule Committee • Goal • to simplify rule • allow new low-drift technologies • Possible modifications to wind speed • Maintain application zones (1, 2, 3, 4) • Plan to release proposed revised language in 2009 for comment • Public meeting(s) will be held
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 • New herbicide chemistries • Environmental impact • Water and Air Quality • Public more aware of pesticide concerns! (Negative) (Perceptions) • Result-higher costs-$$$
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
Droplet Size • Many herbicide labels specify droplet size • Use minimum of MEDIUM droplet size • Determined by • Nozzle type and size (e.g., TeeJet XR8003) • Pressure at nozzle (e.g., 30 psi) • Products and adjuvants • Aerial • Nozzle deflection angle • Airspeed
Droplet Spectra from Aircraft • Composite results • VMD = 510 • VD(0.1) = 252 • VD(0.9) = 727 • GPA = 9.30 • Target Rate (GPA): 5 • Target Swath (Ft): 85 • Application Height (Ft): 13 • Ground Speed (MPH): 106 • Wind Velocity (MPH): 17 • Wind Direction(deg.): 160 • Temperature (F): 69.1 • Humidity (%): 29
Droplet Spectra from Aircraft Target Rate (GPA): 5 Target Swath (Ft): 80 Application Height (Ft): 15 Ground Speed (MPH): 140 Wind Velocity (MPH): 10 Wind Direction(deg.): 220 Temperature (F): 85.2 Humidity (%): 15 • Composite results • VMD = 329 • VD(0.1) = 196 • VD(0.9) = 467 • GPA = 2.042
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.
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.
Wind Speeds Gradients 30 ft 20 ft 10 ft 6 ft 2 ft 0 ft 11 mph 10 mph 8 mph Height Above Crop Canopy Wind Speed 7 mph 5 mph The relation between height above the canopy of a crop like wheat and the speed of wind.
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
Recognizing Inversions • Under clear to partly cloudy skies and light winds, a surface inversion can form in the afternoon. • 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 Fall Distance Wind
Reducing Droplet Drift Summary • 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
Also Pay Attention to Volatilization! • WSDA rule only mentions ambient air temperature • Roadsides/noncrop areas often lack vegetative cover • Target area is hotter than ambient air • Resulting in volatilization Ambient Air - 83°F Gravel area – 105.1°F
Prevent Volitalization Damage • Both old and new herbicide chemistries can cause significant damage to off-target plants • Crops, ornamentals, wildlands, roadway trees and shrubs
In Conclusion Minimizing spray drift is in the best interests of everyone. Do your part to keep applications on target.
Acknowledgements: Slide materials were adapted by Carol Ramsay Washington State University from presentations developed by Dr. Bob Wolf Kansas State University firstname.lastname@example.org View other application presentations at www.bae.ksu.edu/faculty/wolf/