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Credit: Photos: BASF

Backpack applications in which premixed truck tanks are used to fill backpacks reduces the amount of contact applicators have with herbicides.
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Credit: Photos: BASF

Today's sprayer technology allows applicators to direct herbicide flow with precise accuracy.

Creating an effective vegetation management program for rights of way (ROW), requires a method capable of controlling undesirable species without substantially harming desirable vegetation. Backpack herbicide applications often are used to meet vegetation control objectives in key ROW areas because they have the ability to be selective and enable applicators to determine which species to treat. Such applications can be conducted in areas with low to medium density, but should not be done in high-density sites or where brush is more than 20 feet tall. For high-density sites, it's generally more effective to use higher broadcast application equipment, such as a truck sprayer—or an aerial application by helicopter, when sites are completely inaccessible.

Applicators working to achieve control in high-density sites may also want to consider mechanically mowing the site, then spraying the regrowth the following year using a low-volume herbicide. Following with herbicides is crucial because undesirable vegetation will grow back even thicker than before if a high-density area is mowed without taking additional measures. Low-volume backpack, foliar applications are effective on most terrain and highly selective to target brush, while preserving the richness of vegetative species. This method efficiently treats individual tree foliage or brush with low to medium density, in heights up to 20 feet.

Low-volume herbicides allow many more acres to be treated while using the same net volume of herbicide. This means fewer tank refills for backpack sprayers and trucks, giving applicators more time in the field to cover more acres in a day than would be possible with high-volume herbicides. The mix for a typical low-volume herbicide application might include 0.5% low-volume herbicide, with 5% glyphosate and 0.5% nonionic surfactant mixed on a volume per volume basis. Typically, 3-and 4-gallon backpacks are used for such applications.

The closed-handling system, a relatively recent development in backpack spraying technology, makes tank mixing even more convenient. Closed-handling systems allow applicators to mix multiple backpack loads in 15-gallon kegs on trucks, rather than mixing each backpack separately. The truck's pumping system can feed premixed herbicide directly into individual backpacks, increasing ROW efficiency, reducing work stoppages for herbicide measurements, and limiting the amount of contact applicators have with herbicides.

Advanced backpack application technology includes new spray nozzles and wands. Today's sprayers have pressure-sensitive triggers and an innovative swivel valve featuring two interchangeable tips on the hand gun. This design provides optimal spray coverage for low-lying growth as well as growth up to 20 feet. Applicators can use a straight-stream of fanned-out spray pattern, depending on vegetation height. Popular swivel-valve options include:

  • Using a flat-fan tip on one side, with the most popular size being 4004, which means the tip sprays low-growing vegetation at a 40-degree angle and 0.40 gallons per minute at 40 psi. With a flat-fan tip, applying herbicide in a zigzag spray pattern is effective for vegetation at or below 2 feet tall.
  • Installing an adjustable cone tip on the swivel-valve's opposite side allows applicators to reach into the crown of higher-growing trees.
  • When spraying by backpack, applicators need to be mindful of blow-through on ROWs, particularly near a ROWedge. Some herbicides used on ROWs have soil activity, which can lead to unintentional damage of desirable vegetation. To avoid blow-through on the edge of ROWs, a fan-spray pattern should be used in place of the straight-stream pattern, and spray handguns should be kept parallel to the ROW.

    — Todd Horton is a market development specialist with BASF Corp., which is headquartered in Florham Park, N.J.