Understanding Spray Drift. Why Interest in Drift?. Spotty pest control Wasted chemicals Off-target damage More high value specialty crops Less tolerant neighbors Litigious Society Result-higher costs-$$$ More wind?? (Timing) Environmental impact Water and Air Quality
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Movement of spray particlesand vaporsoff-target causing less effective control and possible injury to susceptible vegetation, wildlife, and people.
Vapor Drift - associated with volatilization (gas, fumes)
Particle Drift - movement of spray particles during or after the spray application
- unpredictable & variable in ALL directions.
Structures drastically affect wind currents
Adapted from Survey of Climatology:
Griffiths and Driscoll,
Texas A&M University, 1982
Wind speed - knots, feet/min, meters/sec, mph
Maximum, average, current wind speed
- knots, feet/min, meters/sec, mph
Maximum, average, current wind speed, temp, wind chill- knots, feet/min, meters/sec, mph
All wind speed features plus temp, wind chill, dew point, heat index, relative humidity
Plastimo Iris 50**
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)
One micron (m) =1/25,000 inch
paper clip 850 (m)
staple 420 (m)
toothbrush bristle 300 (m)
sewing thread 150 (m)
human hair 100 (m)Comparison of Micron Sizes for Various Items: (approximate values)
*USDA ARS College Station, TX
Volume Median Diameter (VMD)
1/2 of spray volume = larger droplets
High Relative Humidity
Low Relative Humidity
Demonstrates Turbo Flat vs TurboDrop-5 MPH Wind
Allow enough time for:
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.