Pesticide Safety Education Program General Standards (Part 2 of 8)

February 11, 2017



Study Guide for General Standards Pesticide Applicator Exam Illinois (2017)


Part 2 of 8 – Pesticide Application and Drift Reduction


There are three major types of applications:

  • Spot applications treat only a portion of the total area and are used to control pests that are grouped or clustered.

  • Band applications treat only a narrow strip over or alongside a row of desirable plants.

  • Broadcast applications treat the entire area or field.

Overlap is the portion of a spray pattern that applies over the adjoining pattern. Proper overlap is needed for uniform spraying.

  • Nozzle spacing and spray height determine the overlap on a boom sprayer.

    • Raised boom

    • Lowered boom

Components of liquid application equipment.

  • Pump: moves liquid and creates pressure needed to spray the pesticide solution

  • Tank: holds pesticide solution

  • Agitation: portion of solution that is circulated back to the tank. Mixes pesticides to prevent them from settling out to bottom of tank

  • Strainers: mesh filters that prevent foreign objects in the spray solution from clogging or damaging the equipment

  • Pressure gauge: monitors pressure to ensure equipment is operating properly

  • Pressure and flow control valves: controls the flow of solution and prevents excess pressure

  • Nozzles: delivers the spray to the target – very important component

The type of nozzle and how it is used are important for controlling:

  • The amount of spray applied - flow rate of spray determined by orifice size

  • The uniformity of the spray – determined by nozzle pattern and overlap

  • Coverage of the target influenced by drop size

  • The potential for drift – influenced by droplet size

  • Droplet size influences coverage of target and spray drift

  • Small spectrum: provide better coverage, but more likely to drift

  • Nozzles produce a range of droplet sizes: droplet spectrum

  • Choose nozzles that provide good coverage for intended use and minimize drift

Sprayer maintenance and cleaning prevents damage and misapplications

  • Use clean water

  • Check and clean strainers daily

  • DO NOT use metal objects to clean nozzle

  • Flush new sprayer before using

  • Clean ALL sprayer components

    • Commercial cleaners recommended, especially with newer, more complex formulations

    • Consult label and use prescribed product specific cleaners (if applicable).

Drift Reduction

Drift is the physical movement of a pesticide through air at the time of application or soon thereafter, to any site other than that intended for application.

  • Pesticide drift is the number one complaint about pesticide use.

  • There are two types of pesticide drift:

    • Vapor Drift: movement of pesticide in vapor or gas form

    • Particle Drift: movement of spray droplets

      • Associated with application procedures and weather

      • The primary focus in drift control

There are many problems associated with pesticide drift:

  • Non-target damage

  • Poor pest control

  • Contamination of soil and water resources

  • Loss of money associated with:

    • Re-treatment

    • Wasted pesticide

    • Fines and lawsuit damages

  • Negative public opinion

  • Product cancellation

  • Stricter labels

Particle drift is primarily influenced by droplet size, wind speed and wind direction

Equipment factors that influence drift:

  • Nozzles

    • Affect droplet size

    • Smaller droplets are more likely to drift

    • Orifice size determines droplet size

    • Some nozzle types designed to reduce the number of small droplets

  • Boom Height

    • Determines distance spray travels to target

    • Shorter distance means less exposure to wind

  • Pressure

    • Higher pressure results in smaller droplets

    • Automatic rate controllers – increase in pressure with increase in speed

Weather factors that influence drift

  • Wind speed

    • High wind speeds increase drift

    • Spray particles carried greater distance

  • Wind direction

    • Drift occurs downward of application

    • Location of pesticide sensitive non-target areas

  • Shifting wind speed and direction

  • Temperature and humidity

    • High temperatures increase evaporation

    • Low humidity (dry conditions) increases evaporation

    • Increased evaporation reduces droplet size

  • No wind conditions and inversions

    • Small droplets remain suspended in air

    • Can move off-target long distances

Application strategies for reducing drift

  • Control droplet size spectrum

    • Use nozzles which reduce small drift pone droplets

    • Reduce application pressure – watch rate controllers

    • Use drift reduction additives that increase droplet size

  • Lower boom height – be sure to maintain adequate overlap

  • Increase spray application rate – using higher spray application rates often means using nozzles with a larger orifice, which also increases spray droplet size

  • Do not spray when:

    • Wind speed is greater than 10 mph

    • Wind is blowing towards sensitive areas

    • Winds are shifting

    • During periods of calm or during an inversion

  • Leave an unsprayed buffer zone downwind – return to spray when wind is right

  • When available, use less volatile formulations

  • Keep up to date with pesticide application technology










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