Bruce Alber

Since most family forest owners don't own a helicopter for spraying their lands, many use a backpack sprayer. This tool can be used in many ways to control competing vegetation that will help your trees survive and grow better.

Backpack sprayers are very versatile. You can mix herbicides to spot spray noxious weeds, basal spray bigleaf maple clumps, spray a spot to kill grasses around your new seedlings, or even broadcast spray entire areas.

Several brands of good sprayers are available including Solo®, Hardie®, Cooper-Pegler® and Field King®. A good sprayer has a tank that holds two to five gallons of liquid, a lever arm for pressurizing the pump, comfortable shoulder straps, a hose, trigger, wand and a selection of nozzles.

Additional features to look for in a sprayer include a pumping lever arm that can be fitted on either the left or right side, a large top opening for filling with water and chemical and smooth pumping action. To prevent chemical mixes from dribbling down your neck when you bend over, a one-way valve on top of the filling cap that lets air in but stops liquids from coming out is very important.

For general spot spraying of small weeds, select a flat fan nozzle, use an herbicide such as Accord® and spray the target lightly to wet. Keep the pumping pressure low to reduce drift of fine droplets. High pressure produces large numbers of tiny, driftable droplets that may blow onto desirable vegetation or trees and damage them.

To control brush and resprouted tree species, mix Garlon 4® in W.E.B. Oil™ and spray the lower 12 inches of the stems lightly to wet. This is called basal spraying. This method works very well on bigleaf maple, alder and most brush. The backpack wand works well in reaching around the sides and back of the stems for complete coverage. For larger clumps, walk around them and spray from two or three sides to ensure complete coverage. An adjustable cone-jet type nozzle works well in this type of spraying.

Research has demonstrated that starting seedlings in a weed-free environment results in excellent survival and rapid growth. To achieve this, an area about four feet in diameter can be sprayed with herbicides such as Oust®, Velpar® or atrazine. Since these are soil-active chemicals (they attach to the soil, kill weeds and prevent seed germination), they must be sprayed on very evenly.

If you just spray around a tree by circling it with droplets, the area next to the tree will receive the most soil active chemical, potentially damaging the seedling. To solve this problem, you can buy a Meter-Jet® to attach to the hose from the sprayer. This unit has a trigger, adjustable liquid meter, and a wand and nozzle. Set the meter for 12 milliliters per trigger pull and the special cone nozzle will spray about a five-foot circle evenly over the top of your tree. This even application ensures that the weed control will be consistent, and that the tree will be safe.

When using any herbicide with your backpack sprayer, remember to always carefully read and follow the directions on the chemical label. The label indicates the personal protective equipment (PPE) to wear such as a long sleeve shirt, long pants, unlined waterproof gloves, and my favorite, shoes and socks. Improvising Tree Farmer

Dale Arola of the Clark County Farm Forestry Association has developed an attachment for his Hardie® backpack sprayer that sprays an 11.5-foot swath behind him. To make all-day spraying more comfortable, Dale discarded the shoulder straps on the sprayer and attaches it to a backpacking frame with better shoulder and chest straps, and a padded hip belt to help distribute the load. Other parts include hose, 2-inch x 2-inch piece of wood, sheet metal, nozzles and a valve.

The spray boom is attached to the rear of the sprayer and is height adjustable for low grasses to waist high brush spraying. There are five 80-degree flat nozzles on the boom, and a mid-point shut-off valve so he can spray 5 feet wide or up to 12 feet wide. When filled with 3½ gallons of spray mix, he can spray one-third of an acre per fill up. The full pack weighs 52 pounds and Dale can broadcast spray five to seven acres per day.

He and other members of the Clark County Farm Forestry Association have assembled these sprayers in group meetings, so many other tree farmers are using this system now. Production costs are far less than an hour of helicopter time!

Bruce Alber is a forester for Wilbur-Ellis Co., in Portland, Ore. He can be reached at (800) 727-9186.

This article appeared in the Northwest Woodlands Magazine, -Published quarterly by the World Forestry Center as a benefit of membership in the Oregon Small Woodlands Association, Washington Farm Forestry Association, Idaho Forest Owners Association and Montana Forest Owners Association.

The mention of certain brand names and products does not constitute an endorsement of one product over another by Northwest Woodlands.