Oregon State University Extension Service

Eliminate unwanted vegetation

Methods that are designed to suppress or kill unwanted vegetation. Remember, dead plants are fuels, so any dead woody material that occurs as a result of herbicide application must be piled and burned or removed and disposed of to reduce the fire hazard.

Prepare the sprayer

Always read the label of the herbicide container.  Some herbicides need to be mixed with a non-ionic surfactant before use.  Alternatively, an herbicide may need to be mixed with water.  Check the label to be sure.  If mixing water, use only clean water.  Mix the herbicide with the required base in a separate bucket.  Stir the mixture thoroughly before transferring to the spray backpack. 

If the backpack sprayer has been previously used with a water-based herbicide, be sure to empty out the sprayer.  Add a small portion of oil to the sprayer and pump it through to the nozzle to ensure all water has been removed from the hose.  Finally, add the oil-based herbicide into the backpack sprayer.  Failure to clean out the water-base from the sprayer will result in a white material that may clog the sprayer.

Hack/Frill or Girdle and Squirt

Used for standing trees. One or more cuts is made into the trunk (or large branch) of a tree, or the tree is girdled and a very small amount of concentrated herbicide is squirted into the cut area. This is usually an effective method for killing unwanted trees; however, the dead, standing trees are fuel and should be removed when fire and fuel loading are a concern.

Foliar spray 

Used for brush and stump sprouts. The foliage of the plant to be controlled is sprayed to wet the foliage thoroughly, but not to the point of runoff. These are usually spot spray treatments applied with a backpack sprayer. Applications are usually made during the mid to late growing season, depending on the species to be controlled.

Basal treatment

Used for brush and stump sprouts. Provides for selective removal of individual plants. The herbicide is mixed with an oil carrier (e.g., seed oil) and applied directly to lower stems of trees or shrubs to be controlled.

Cut stump

Used for trees and stump sprouts. Concentrated herbicide (typically, half to full strength) is applied to the outer area of a freshly cut stump.

Source URL: https://extension.oregonstate.edu/pests-diseases/pesticides/eliminate-unwanted-vegetation