Pesticide Drift ManagementCurtis Rainbolt, Les Baucum, and Ron Rice

Pesticide Drift ManagementTopics For Discussion

• Definition

• Types of drift

• Factors affecting drift

• Management

What is Pesticide Drift?

• Drift- movement of spray particles beyond the designated target

• Two types:– physical drift– vapor drift

Drift (continued)

• All movement to off label crops is illegal

• Chemical drift is an unavoidable part of pesticide application

• Managing spray drift is the responsibility of the applicator

Spray drift is undesirable!

• Inefficient use of equipment and time

• Under-application/ineffective control

• Crop damage and litigation concerns

• Unintentional contamination

• Air/water pollution

• Environmental and human health/safety

Physical Drift

• Movement of pesticide away from target during application

• Influenced by:– Droplet size– Boom height– Weather

Physical DriftWeather

• Wind speed/direction

* most important

• Soil moisture

• Temperature

• Humidity

• Inversions

• 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

Drift Potential May be High at Low Wind Speeds

Physical DriftDroplet Size

• Measured in microns

• 20-370 micron range

• 200 micron average

• Smaller drops increase drift potential (< 100)

Fall Rate of Various Size Droplets

Droplet Diameter(microns) Time to Fall 10’

20 4 mins.

100 11 secs.

240 5 secs.

400 2 secs.

Relationship of Particle Size to Drift

Drop Diameter (microns)

Particle Type

Drift

Distance 400 Coarse 8.5

150 Medium 22.0

100 Fine 48.0

Based upon 10’ fall in 3 MPH windsBased upon 10’ fall in 3 MPH winds

Physical DriftIdeal Spray Boom Height

SprayAngle 20” 30”

65 22-24 33-35

80 17-19 24-26

110 15-18 20-22

Spacing

• Wide-angle nozzles can be placed lower to the target, but also produce smaller droplets.

• Easy and inexpensive

Physical DriftOther Factors to Consider

• Nozzle selection

• Spray pressure

• Spray volume

Turbulence-Chamber and Air-Assist Nozzles

• Allow air into a mixing chamber creating a vacuum that mixes the air and spray solution

• Forms large bubbles that do not drift as far

Greenleaf, TurboDrop

Turbo TeeJet

Influence of Spray Pressure on Droplet Size

Flat Fan Nozzle - 0.6 GPM

12

6

0

5

10

15

20 PSI 40 PSI

Pressure

% D

ropl

ets

100

mic

rons

or

less

Pesticide Drift ManagementDrift Control Agents

• “thickeners”

• increase droplet size of pesticide/water mixes

Vapor Drift

• The volatilization or evaporation of a pesticide from the soil or crop surface that occurs after application

• Vapor drift is influenced by:

* vapor pressure/volatility

* temperature

* wind speed

Non-TargetSensitive Crop

Vapor drift can occur even days after the application

Wind

Drift

Vapor

Six Ways to Reduce Drift

1. Check the wind speed and direction

2. Read the pesticide label

3. Use nozzles that produce large droplets

4. Lower your application pressures

5. Lower your boom height

6. Be aware of your surroundings

References used in the development of this slide set include :

• Strategies for reducing herbicide drift, Iowa State University, Brent Pringnitz, http://www.weeds.iastate.edu/mgmt/qtr99-1/nozzles.htm

• Kansas State University's Application Technology Project website http://www.bae.ksu.edu/rewolf/

• Pesticide Drift Management, University of Georgia, Eric Prostko http://www.cropsoil.uga.edu/weedsci/slides/drift/

• Herbicide Spray Drift, North Dakota State University, http://www.ext.nodak.edu/extpubs/plantsci/weeds/a657w.htm

• Reducing Spray Drift. Ohio State Univ. Extension Bulletin 816, H. Erdal Ozkan.

• Herbicide Application Management. Sandoz Crop Protection, 1993.