January 2016


Consider chemical side trim applications

Whether managing rights-of-way or roadsides, trees can pose a special challenge for vegetation managers. To keep power lines clear or roadsides safe, vegetation managers have several options when trees encroach: cut the tree down; mechanically side trim the tree; or use herbicides to either partially control growth (chemical side trim) or control the entire tree. Choosing mechanical cutting can present worker safety issues and be very time-consuming and expensive.

An alternative to mechanical cutting is the use of herbicides to control the growth of portions of tree limbs that could affect power lines or roadsides access, safety and visibility. Certain herbicides, when used correctly, can effectively “prune back” only the treated tree limbs while not controlling the whole tree. This is called a chemical side trim application — the herbicide is only applied to the branches of the trees that pose a threat to the right-of-way. This keeps the tree alive, healthy and more aesthetically pleasing, while removing only the problem area of the vegetation.

Making the application.
Chemicalsidetrim2_250Chemical side trim programs require much less equipment and fewer people, and are a safer, more cost-effective alternative to mechanical trimming programs. When cutting tree branches along powerlines or roadsides, tree crews must safely cut the limbs, clean up the removed branches and will bring a wood chipper, trailers or trucks to haul debris and other support equipment to the site.

Chemical side trim applications are much quicker to perform than mechanical, so there is less exposure to risky situations, such as traffic on roadside rights-of-way. These applications can be made from truck-mounted sprayers or from bucket trucks either as a foliar or dormant-stem spray application. Foliar applications are made by spraying the herbicide mixture directly onto the encroaching leaves, limbs and branches when the tree is actively growing. Dormant applications are similar to foliar, but applications are made to limbs and branches during the winter when deciduous trees are without foliage.

These applications affect only the area that is sprayed, leaving the rest of the tree alive and healthy as long as lower and/or mid-canopy branches are treated. Be sure not to treat the crown of the tree unless full control of the tree is desired.

Equipment options for making applications are basically the same as foliar programs. Truck-mounted manifold or controlled droplet sprayers are very effective, but total volume per acre is generally higher to achieve thorough wetting of the target dormant stems and can go as high as 100 gallons total solution per acre for high-density sites, and large limbs and branches. Also, handgun applications applied from ground, truck or bucket truck provide excellent chemical side trim control; but higher total volumes are generally needed to achieve complete coverage.

Chemicalsidetrim3_250Perfect treatment for the dormant-season.
Dormant-season applications offer several benefits that make them attractive alternatives to foliar chemical side trim programs. First, applications are made during the winter and very early spring so spray drift to desirable crops and sensitive foliage is generally not a concern. Also, because applications are made to hardwood limbs and branches that have dropped their leaves, there are minimal brownout issues; only limbs and branches of conifers or other evergreens show brownout.

Further, dormant-season chemical side trim applications extend the traditional application window, allowing application during the typically less busy winter months. Here are a couple of important notes to keep in mind around application timing and conditions:

  • Applications should be made during mid- to late winter and very early spring — typically from early January through late March. Depending on geographic location, this timing can vary.
  • All dormant applications should be completed before foliage begins to emerge on deciduous trees.
  • The ideal application timing is about six weeks prior to bud break up to the beginning of bud break (or for the PNW see the table below for timing of applications).
  • Applications must be done in dry conditions — meaning bark, stems and branches must be dry.
  • Applications made when bark is wet will cause the spray mix to emulsify (turn milky white) on the stems, and side trim efficacy will be significantly reduced.

Chemicalsidetrim4_250Only emulsifiable concentrates/oil-soluble herbicides can be used for dormant side trim treatments. Garlon® 4 Ultra specialty herbicide is an oil-soluble formulation and is the key to a successful dormant side trim program. Typically, 2 gallons of Garlon 4 Ultra plus 2 to 3 gallons of crop oil concentrate (COC) are mixed per 100 gallons of water. Add 7 fluid ounces of Milestone® specialty herbicide for enhanced conifer and evergreen control. Applications are made to limbs and branches to thoroughly wet them, but not to the point of runoff. More specific treatment recommendations can be found here.