Weed control demonstrations

Basal bark method

This method involves mixing an oil-soluble herbicide in diesel and spraying the full circumference of the trunk or stem of the plant. Basal bark spraying is suitable for thin-barked woody weeds and undesirable trees.

Basal bark spraying is also an effective way to treat saplings, regrowth and multi-stemmed shrubs and trees. This method allows the herbicide to enter underground storage organs and slowly kill the targeted weed.

The entire circumference of the stem or trunk should be sprayed or painted with herbicide solution from ground level to a height of 30 cm. It is important to saturate the full circumference of the trunk, and to treat every stem or trunk arising from the ground.

Basal bark spraying is a very effective control method, and is a good way to tackle inaccessible areas such as steep banks. This method will usually kill difficult-to-kill weeds at any time of the year, as long as the bark is not wet or too thick for the diesel to penetrate. The work is often best performed by contractors.

Cut stump method

The plant is cut off completely at its base (no higher than 15 cm from the ground) using a chainsaw, axe, brushcutter or machete (depending on the thickness of the stem/trunk). A herbicide solution is then sprayed or painted onto the exposed surface of the cut stump emerging from the ground, with the objective of killing the stump and the root system.

It is imperative that the herbicide solutions are applied as soon as the trunk or stem is cut. A delay of more than 15 seconds for water-based herbicides and one minute for diesel-soluble herbicides between cutting and applying the chemical will give poor results.

Two operators working as a team can perform this method effectively. The herbicide can be applied from a knapsack, or with a paint brush, drench gun or a hand spray bottle. It is a good idea to use a brightly coloured dye in the solution to mark the stumps that have been treated.

For trees with large circumferences, it is only necessary to place the solution around the edge of the stump (as the objective is again to target the cambium layer inside the bark). The stump circumference should be bruised with the back of an axe and each successive blow treated with herbicide.

This method has the appeal of removing the weed immediately, and is used mainly for trees and woody weeds. This method is also referred to as cut and spray, or cut and paint.

Cut and swab method

This method is similar to the cut stump method, but is suited to vines and multi-stemmed shrubs. Here, the plant stems are cut through completely, close to the ground. Herbicide is then applied immediately to the cut surface emerging from the ground, via spray or brush application.

In the case of Madeira vine and some other vines with aerial tubers, both ends of the cut stems must be treated with herbicide. An effective way of doing this is to hold both 'bunches' of cut stems in a container of herbicide for 15 seconds after cutting, so that maximum translocation occurs to both ground and aerial tubers. Extra care should be taken when doing this to ensure spillages do not occur.

Further information

Last updated 04 November 2011