October 2015


Choose Your Backpack Sprayer Wisely: Then Maintain it for Maximum Effectiveness

Individual plant treatments are highly effective herbicide applications that should have a home in the toolbox of every vegetation manager. By nature, they allow for targeted vegetation control of brush less than 10 feet in height with little danger of off-site and non-target species damage, especially when selective herbicides are used. One of the most common pieces of equipment used in individual plant treatments is the backpack sprayer. This versatile sprayer offers users several important benefits, says Pat Burch, field scientist with Dow AgroSciences.

“Using a backpack sprayer allows an applicator to selectively treat target vegetation, thereby reducing the risk of non-target damage,” Burch says. “They are also simple to operate and relatively inexpensive to purchase and maintain. Finally, a backpack sprayer’s portability means it can be used anywhere an applicator can reach by foot, including difficult terrain.”

However, he adds that users should take the time to select the best-suited backpack sprayer to their needs, and then must properly maintain it to realize these benefits.

Selecting the right sprayer
Backpack sprayers come in all sorts of variations, so it’s important to purchase the kind that will work best for the intended end use. For starters, durability of the equipment is important, as is the availability of repair parts should something fail.

Another consideration is the area to be treated. “If treating large areas, a motorized pump might make sense to help alleviate operator fatigue,” says Burch. “However, it adds expense, makes the unit heavier and increases maintenance needs.”

Most sprayers come equipped with either a diaphragm or piston-style pump. A piston-style pump produces higher pressures more easily and works well with non-abrasive chemicals, but generally, a diaphragm pump is more durable and able to be used with a wider variety of herbicide formulations, including dry-flowable formulations such as Opensight® specialty herbicide.

A good spray wand is also important, as it is less susceptible to leaks and delivers a more accurate herbicide application. Selecting a wand that accepts TeeJet nozzles allows the user to switch out and use a wide assortment of nozzle types depending on the application being made.

Finally, Burch cautions: “If using it to apply oil-based carriers (basal oils) for woody plant control, make certain your sprayer is equipped with parts (pumps, hoses, etc.) that are resistant to oil-based carriers,” Burch says. “Otherwise, the oil will break these parts down over time.”

Easy maintenance tips
With the right backpack sprayer selected, keep it working properly with a couple easy maintenance tips.

“Most important, applicators should thoroughly clean their sprayers after every use. This is as simple as rinsing the equipment at the end of the day by using clean water or a tank cleaner,” Burch says. “This will prolong its life span and cut down on the amount of repairs needed.”

Care should be taken with any herbicide left in tanks — always consult the herbicide label for more information on safe handling and disposal.

If in a colder climate, it’s also essential to winterize sprayers before cold storage. This can be done by adding automotive or RV antifreeze to the tank to prevent freezing.

Finally, if recommended by the manufacturer, be sure to lubricate all seals and O-rings at the start of the spray season. Lubricate them again midseason if the unit sees heavy use.

Calibrating for use in broadcast applications
If using the backpack sprayer to apply a fixed broadcast rate per acre, calibrating it is a simple, but necessary process. Before beginning, remember 1 gallon is equal to 128 fluid ounces. Therefore, the calibration spray area should be sized to 1/128 of an acre. This will ensure the fluid ounces collected during calibration equates to gallons per acre.

backpack_sprayer2“First, make sure the sprayer and nozzle are clean, and fill the tank with clean water,” Burch says. “Spray some water on a surface to ensure the nozzle is working properly. Select a spray tip that provides a uniform pattern for the area you are treating.”

Then, measure an area 18.5 by 18.5 feet, or 1/128 of an acre, in a field where the spray will be applied. Time the number of seconds it takes to spray the measured area uniformly by using a gentle side-to-side sweeping motion with the spray wand. Repeat this step and average the two times.

Maintaining a constant sprayer pressure, spray into a container for the average time just calculated, and measure the number of fluid ounces in the container. This number is in fluid ounces and is equivalent to the number of gallons per acre the sprayer is delivering. For example, if 3 fluid ounces of water is collected in the container, the sprayer will deliver herbicide solution at a rate of 3 gallons per acre.

“Following these simple steps to select and maintain a backpack sprayer will ensure more consistent and effective results when applying herbicides,” says Burch. More information on backpack sprayers and individual plant treatments, including how-to videos, can be found here.