Control Unwanted Trees Using Hack-and-Squirt Herbicide Applications

June 25, 2019

UNIVERSITY PARK, Pa. -- Dense understories of undesirable shade-tolerant trees including red maple, American beech, blackgum, black birch, striped maple, and eastern hophornbeam interfere with the establishment and development of desirable regeneration such as oak, cherry, and poplar. Researchers have concluded that diversity declines as shade-tolerant tree species continue to expand. Recognizing and treating less-desirable trees increases the proportion of desirable species in future timber stands.

Removing or deadening undesirable trees is a forest man¬agement tool owners can employ to achieve their objectives. It allows the owner to favor species better suited to the site that meet desired conditions and objectives. The most effective method for deadening undesirable standing trees involves the use of herbicides.

Hack-and-squirt, also known as frill and spray, herbicide applications are one of the most target specific and economical means for controlling unwanted trees. Applications made to undesirable trees facilitates the regeneration or growth of desirable species. Hack-and-squirt applications are effective on various size stems and are applicable in hardwood stands where mechanical broadcast spray treatments are not feasible or desirable.

Hack-and-squirt applications introduce the herbicide into the stem using spaced cuts made at a convenient height around the trunk. Using a hatchet, downward-angled incisions are spaced evenly around the stem, one per inch of diameter (two cuts minimum).

Cuts are approximately 2 inches long and spaced 1 to 2 inches apart. The cuts must penetrate through the bark into the living tissue or sapwood and produce a cupping effect to hold

the herbicide. Each cut is filled with herbicide using a spray bottle.

Hack-and-squirt herbicide applications are effective at any time of the year, except during heavy spring sap flow. Applica¬tions made during periods of heavy sap flow are inef¬fective. In addition, do not treat when trees are solidly frozen. When hard freezes are forecasted to occur at night following application, add RV antifreeze (propylene glycol) to the spray solution according to label directions.

Applications to control root-suckering species such as beech, blackgum, and tree-of-heaven are most effective from July to the onset of fall coloration.

Hack-and-squirt applications are target-specific treatments generally used to control trees that are 1 inch in diameter and greater. They are most commonly used in hardwood forest timber stand improvement projects to deaden less desirable trees. These applications are often used to help establish desirable regeneration by removing low shade cast by dense understories of undesirable saplings and poles (trees 4-10 inches in diameter). Hack-and-squirt treatments control competition without impacting existing regeneration or desirable residual trees. Hack-and-squirt is also effective for releasing crop trees in hardwood stands. In addition, hack-and-squirt can be used to create standing dead trees, called snags, to provide desirable wildlife habitat.

Herbicides used for hack-and-squirt applications are water-soluble systemic materials, meaning they move vertically and horizontally within the tree. Numerous “general use” products have labels for hack-and-squirt applications, meaning forest landowners can purchase these products and apply them to their own properties without cer¬tification.

Traditional understory treatments have used mechanized (skidder-mounted) mist blowers. For a more selective application, consider hack-and-squirt treatments. They offer one of the saf¬est, most efficient, target-specific, and least expensive means of eliminating unwanted trees. The herbicides used are non-restricted and control a wide range of common spe¬cies. Hack-and-squirt provides a flexible tool landowners and managers can use to accomplish a variety of vegetation man¬agement objectives over a wide range of forest types.

For more detailed information view the new Forest Science Fact Sheet entitled Using Hack-and-Squirt Herbicide Applications to Control Unwanted Trees by visiting the Penn State Extension website at https://extension.psu.edu/using-hack-and-squirt-herbicide-applications-to-control-unwanted-trees or call 814-355-4897.

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EDITOR: For more information, contact Dave Jackson (814-355-4897, drj11@psu.edu).