Backpack sprayers can be used to control invasive species, herbaceous vegetation and woody shrubs and trees, prepare areas for raking straw, and release pine seedlings from competition. Non-commercial-grade sprayers can often be purchased for less than $100 at farm and garden supply stores, home improvement centers, or online.
It is necessary to properly calibrate the sprayer prior to use to ensure that the herbicide is applied at the rate recommended on the label, which is a legally binding document. This will provide adequate control of target species, limit damage to non-target species, reduce product waste, and prevent misuse of active ingredients.
Calibration is especially important when the difference between the effective per-acre rate of the active ingredient used and the rate that could have residual negative effects on the site is small. These are the area method and 128-acre method for herb applications, and the spot method for vines, shrubs, small trees, and densely clumps or vertically growing vegetation.