Hitting The Target

What sprayer set-up offers the best coverage and reach into the canopy?

By Amanda Huber

Timely and effective pesticide applications are critical to protect yield and quality from pests throughout the season. Simerjeet Virk, University of Georgia Extension precision ag specialist, says several factors can influence the coverage and efficacy required during spray applications for effective pest control.

Pressure, volume, boom height, droplet size, tractor speed and field conditions are all factors that play a part in good crop coverage, and for peanuts, good penetration into the canopy.

Choose A Multi-Nozzle Assembly

The nozzle is one of the least expensive parts on a sprayer that has the most effect, Virk says.

“If you have a worn nozzle or the wrong size or type, the chances of something going wrong are significantly increased.”

Nozzle type affects sprayer output, uniformity, coverage and drift. Consult the manufacturer’s nozzle catalog for selecting the nozzle that provides the desired output (flow rate and droplet size) specific to the application. Nozzle selection will also depend on the ground speed and pressure required to achieve the rate in gallons per acre.

“Is there one nozzle that can do the best job across different pesticide applications? Probably not.” Virk says.

In this instance, he recommends using a multi-nozzle turret body.

“You can put three, four or five nozzles, depending on the type of turret body, which will work best for each type of application – herbicide, fungicide or insecticide – as you go through the season. You don’t have to take it on and off. All you do is change the turret to the type of nozzle you need.”

Read And Follow The Pesticide Label

The correct nozzle recommendation, along with pressure, volume and other parameters for effective application, can be found on the pesticide label. Producers should always start pesticide application by reading the label.

Virk and other researchers continue to look at combinations that offer the best coverage and efficacy as well. With assistance from Bob Kemerait, UGA Extension plant pathologist, Virk says a current study is looking at spray volume and droplet size to determine the combination that gives the best coverage and penetration.

“We are looking at three different spray volumes: 10, 15 and 20 gallons per acre, and three different droplet sizes: a medium droplet, one of the most commonly used, a very coarse droplet and an ultra-coarse droplet.

“The reason we are looking at some of these larger droplets is because we have growers who are also cotton growers and one of the questions from them is, ‘Can I use these Dicamba nozzles, which produce large droplets to reduce drift, to spray peanuts throughout the season?’ So, we’re investigating that,” Virk says.

Options For Better Coverage

Virk says they have conducted application-type trials looking at coverage from the top of the canopy, the middle and the bottom of the peanut canopy.

“When spraying peanut fungicides, we need to make sure that the product is reaching the crown of the plant,” he says. “Two outcomes that we have found in our studies is that increased volumes provide better coverage and canopy penetration, as does smaller droplet size. With larger droplets, as much as 50% of that volume can be lost from the pesticide by not reaching down into the crown of the plant.

For most applications, the recommended spray pressure should be between 30 to 50 pounds per square inch, which results in medium to coarse droplets to reduce drift while still providing adequate spray coverage. Virk says producers should be cautious about smaller droplets.

“When you use standard XR flat-fan nozzles with a high pressure, it creates a lot of fine droplets. A little bit of wind and all those fine droplets are drifting.”

Virk says they have found that producers may be losing up to 30% of the volume under these conditions.

“If you do the math, if you are spraying 10 gallons, technically, you are only putting out 7 gallons; 30% is lost to the wind.”

Ground speed also plays an important role in achieving the desired application rate. Faster speeds will cause excessive boom bounce, sending finer droplets higher into the air and increasing the potential for drift. Boom height, too, influences spray pattern and drift. Reduce tractor speed to less than 10 miles per hour and set boom height at 20 to 30 inches from the target for consistent, more uniform coverage and less drift.

Attention to details and time spent on sprayer maintenance, set up and calibration will go a long way to helping ensure effective spray coverage and pest protection. PG

Showing participants at the UGA cotton/peanut research fi eld day a multi-nozzle turret body, Simer Virk, University of Georgia Extension precision ag specialist, says producers could use that technology to keep the three to fi ve mostused nozzles on the sprayer at the same time. • Check pesticide labels for the recommended rate and droplet size requirements to select the best nozzle that meets those application parameters. • Medium to coarse droplets are more e ective for herbicide applications, whereas fungicide applications generally require finer droplets for increased coverage and e icacy. • Maintain consistent ground speed and spray pressure during application to achieve the desired droplet size for optimum coverage and canopy penetration. • Select nozzles for the application rate and droplet size at operating pressures of 30 to 50 pounds per square inch. • Calibrate a sprayer properly to verify the actual application rate in gallons per acre. Spray output should be checked at multiple locations across the boom/spray width. • Increase carrier volume/application rate for improved coverage. Do not lower spray volume below the minimum recommended rate specified on the pesticide label. • Spray at ground speeds of less than 10 mph to obtain consistent and more uniform coverage across the field. • Lower boom height to 20-24 inches above the soil or crop canopy to maintain adequate spray overlap and application uniformity across the boom. • Consider wind speed and direction during spray applications. Avoid spraying when wind speeds are more than 10 mph to reduce o -target movement of pesticides. • Avoid spraying when the conditions for temperature inversions are favorable. • Use a rate controller for flow rate adjustments with changes in ground speed to maintain target application rate throughout the field during spraying. • Advanced technologies such as pulse width modulation (PWM) and auto-boom height can also be utilized to minimize variations in application rate and coverage across the field.

Source: UGA Peanut Production Agronomic Quick Reference Guide