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Spraying Tips

  • Simer Virk, UGA and Eric Prostko, UGA
    Timely and effective pesticide applications in peanut production are important to stay on top of weed,
    insect and disease control throughout the growing season. Achieving both desired spray coverage and
    efficacy while keeping off-target movement of pesticides to a minimum is a challenging but an
    important task. Several factors during spray applications can influence the coverage and efficacy
    required for proper pest and disease management in peanut. Below are several spray considerations to
    maximize the effectiveness of pesticide applications with boom sprayers:
    Timeliness: Being timely with pesticide applications is the most important factor in determining the
    success of any pest management program. Late applications usually will require higher use rates or split
    applications and are more often than not, less effective.
    Nozzle Selection: Check pesticide labels carefully for recommended spray volume, droplet size, and any
    other conditions needed to maximize pesticide efficacy. Based on the application type and pesticide
    mode of action, select the nozzle that provides both the desired output (in gallons per acre or GPA) and
    the droplet size. Nozzle selection will also depend on the ground speed and pressure required to achieve
    the desired GPA.
    Spray Pressure: Spray pattern and droplet size changes with spray pressure. Lower pressures result in
    larger droplets whereas higher pressures produce smaller droplets for a given nozzle size. Based on the
    application type, consider selecting a nozzle that provides the required droplet size in the 30 – 50 PSI
    pressure range. Both medium and coarser droplets are effective for herbicide applications whereas
    fungicide applications generally require medium to finer droplets for increased coverage and efficacy.
    Ground Speed: Application speed plays an important role in achieving the desired application rate. A
    higher travel speed will require a higher nozzle flow rate to achieve the given application rate and viceversa. Spray at ground speeds of or less than 10 mph to obtain consistent and more uniform coverage
    across the field. Faster speeds also cause excessive boom bounce and spray inversion sending finer
    droplets higher in the air and increasing drift potential.
    Boom Height: Boom height influences overlap and uniformity of spray application at a selected nozzle
    spacing and spray angle. Lower boom height (20 to 24 inches from the target) is recommended for
    maintaining a proper spray overlap and application uniformity across the boom. Make sure to use
    nozzles that have a 1100 angle to allow spraying at lower boom heights without effecting spray coverage.
    Environment: Weather conditions such as wind speed and temperature also play a role in achieving the
    desired spray coverage and on-target application. Avoid spraying when wind speeds are more than 10
    mph to reduce off-target movement of pesticides. Wind direction should be also considered to avoid
    spraying towards sensitive crops, homes, etc. Avoid spraying when the conditions for temperature
    inversions are favorable – from later in the day until early in the morning.
    Sprayer Calibration: Proper sprayer calibration is important to verify the desired spray volume (GPA)
    based on the selected ground speed and nozzle spacing. During calibration, make sure to check the
    spray volume at multiple locations across the boom and perform a thorough sprayer inspection to
    ensure proper functioning of all sprayer components.
    Spray Technology: Consider using spray technologies such as a rate controller and section or individual
    nozzle control which helps in maintaining application accuracy across the whole field by minimizing offtarget applications. Advanced technologies such as pulse width modulation (PWM) technology and
    automatic boom height control systems are also currently available to utilize on boom sprayers for
    improving precision and accuracy of pesticide applications.
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