Control Invasive Shrubs in Spring with Basal Bark Herbicide Applications

Basal bark herbicide applications are targeted treatments you can make year-round, yet are particularly effective and simple to apply in spring. Most common invasive shrub species are easily controlled with these applications. They include Japanese barberry, shrub honeysuckles, autumn olive, multiflora rose, privet, and many others. These species are common invaders of woodlands and natural areas across the mid-Atlantic region.

Most invasive shrubs tend to leaf out early in the spring, well before our native tree and shrub species do and before most perennial plants have emerged from the ground. By leafing out early, they can be easily spotted by scanning across the woodland understory or an early-successional meadow. This characteristic makes them easy to find and identify as invasive thus allowing you to detect where these invaders are located.

Basal bark herbicide applications permit you to be very specific in your control efforts. This application allows you to place the herbicide directly onto the stems of the invasive shrubs when native trees and shrubs are still dormant. In addition, because most perennial plants have not emerged yet, applications to lower stems can be made very easily and efficiently. Making applications this time of year greatly minimizes the possibility of damaging desirable native plant species.

Basal bark herbicide applications are made using a low-pressure backpack sprayer with a spray wand to wet the lower 12–15 inches of the stem using a solid cone, adjustable cone, or flat fan nozzle. To be effective, it is important to wet the entire lower stem and root collar, but not to the point that it's running off the stem. Basal bark herbicides use an oil carrier to penetrate the bark and commercially available basal oils come in either mineral or vegetable-based formulations.

To make basal bark herbicide applications, there are a few pieces of equipment you will need, including a backpack sprayer; my preference is a Birchmeier backpack. Birchmeier’s is a commercial-grade backpack with viton seals that will hold up to oil-based formulations. The wand that comes with the sprayer will work, but I would suggest changing the nozzle to a Y-1 or Y-2 brass adjustable cone. If making basal bark applications to large acreage, you may also want to consider investing in the B & G Extenda-Ban low-volume basal wand. This wand is a commercial-grade wand with a shut-off valve built into the tip. This prevents over-applying and dripping product from target to target. It will save you money in the long run.

Numerous products are labeled for basal bark applications. The ester formulation of triclopyr is the active ingredient of choice for most woodland basal applications. It is found in a number of different products, including soluble concentrates (ex. Garlon 4 Ultra, Triclopyr 4, Relegate, Garlon XRT, etc.) as well as some pre-mixed ready-to-use products (ex. Pathfinder II, Triclopyr RTU). Many of the concentrates contain 60– 61% triclopyr ester. For low-volume basal applications using one of these, the basal mixture will usually consist of 20% herbicide product and 80% basal oil.

Some products contain a higher concentration of triclopyr ester (84%) and may be used at a lower percentage in the basal mix (i.e. 13% product and 87% oil). Note, this is the "low-volume" basal application rate where you are applying a concentrated solution to the stem but not to the point where run-off at the groundline is noticeable.

Triclopyr ester is a systemic herbicide absorbed by the plant through the bark and translocated throughout the plant's vascular system. Triclopyr works by disturbing plant growth. It accumulates in plant meristems, cells where growth takes place, causing uneven cell division and growth. Triclopyr binds to soil organic matter and clay particles, which limits its movement in the soil and prevents root uptake by desirable plants. It biodegrades quickly, with half of the active ingredient degraded by soil microorganisms and sunlight within 30–45 days. The herbicide is classified as only slightly toxic with a CAUTION signal word on the product label.

Basal bark herbicide treatments allow for targeted invasive shrub control in spring with little danger of off-site and nontarget species damage, though there usually will be a ring or 'halo' about 1 foot in diameter around the base of each treated stem where broadleaf vegetation will be suppressed for a period of time. These applications are well-suited for treating small-diameter stems. Basal bark herbicide applications provide year-round application flexibility but are particularly effective at controlling invasive shrubs in spring when they are just starting to leaf out. Triclopyr ester herbicides control a wide range of broadleaf species, including the most problematic invasive shrubs. It is a general use herbicide, meaning landowners can purchase and apply it to their own properties without certification in Pennsylvania. Be sure to read and follow the herbicide label, it is a legal document.