Invasive plant control options

The basal bark method is useful for shrubs and trees up to 10cm in diameter, especially those that are multi-stemmed or with a suckering nature that are difficult to stem inject. It involves painting the bottom 30-40cm of the trunk all the way around with a mixture of oil soluble herbicide and an oil based carrier such as diesel, kerosene, bark oil or vegetable oil (as per specified mixing rates for basal bark method). This leaves the root system in tact which can help to prevent erosion.

Bio-control is a method of controlling invasive plants using the plants' natural enemies such as insects. A rigorous testing process is undertaken to ensure that bio-controls are host specific before they are approved and released into the environment. Bio-controls reduce the need to use chemicals and also the cost of invasive plant management. Bio-controls have been released by the Sunshine Coast Council for Salvinia, Madeira vine, Cats claw creeper and Lantana.

Depending on supply and demand you may be able to purchase the following bio-controls from the places below

Bio-control for Cat’s claw creeper and Madeira vine are available from the Mooloolah River Waterwatch and Landcare Inc and Gympie District Landcare

Bio-controls for Salvinia, Water hyacinth and water lettuce from Brisbane City Council

This can be useful for vines, shrubs and trees. This method involves cutting the stem at the base of the plant with secateurs, loppers, hand or chainsaws (depending on the size of the plant). The roots can then be dug out or plastic can be wrapped around the stump of the plant to prevent regrowth.

This method is suitable for woody weeds such as shrubs, trees and vines. It involves cutting the plant at the base with secateurs, loppers, a handsaw or chainsaw (depending on the size of the plant) and applying herbicide to the stump within 15 seconds (any longer than 15 seconds will affect results) to ensure that it is absorbed by the plant.

This method is useful for treating most types of invasive plants apart from some succulents and trees. It involves spraying herbicide onto the leaves of the tree which is then absorbed into the plant. Foliar spray can be applied by a back pack sprayer for smaller areas or a quickspray unit for large scale weed control. Sunshine Coast council has back pack kits and quick spray units for hire.

Hand weeding involves pulling out invasive plants manually or with tools. Make sure that the whole roots, tubers, bulbs or corms are removed and any parts of the plant capable of reproducing, are bagged and solarised or disposed of. This method causes minimal disturbance to the soil and to other plants.

Mechanical options include using larger machinery to remove invasive plants. For example tilling the soil or using an aquatic weed harvester to remove invasive plants from the water.

Mowing, brush-cutting and slashing can be useful for controlling invasive plants by preventing flowering and seed dispersal. This method is not useful for plants that spread by stem fragments or those that flower and seed at different times throughout the year. Mowing these types of plants will spread stem fragments and seeds to other areas. This method is useful for annuals such as annual ragweed and can even be useful for groundsel bush if done annually prior to flowering. Timing is crucial for using this method for weed control.

Pasture improvement and revegetation will help to prevent invasive plants from becoming established or re-establishing, create habitat and prevent erosion where invasive plants have been removed.

Tree poppers can be used to remove woody plants such as shrubs, small trees or weedy vines. Tree poppers are set up at the base of the plant and then using some manual pressure the roots are leveraged out of the ground. Council has tree poppers for hire

Some invasive grasses such as Giant Rats tail grass produce significant amounts of seed. The seed heads will need to be cut and bagged before the rest of the plant is dug out.

This method involves removing the outer layer of a 20cm or more section of trunk all the way around the tree or shrub to prevent nutrients from being transported so that the tree or shrub dies. This method is only suitable where falling limbs of the tree will not cause harm to people, animals or structures.

Smothering invasive plants is usually done on a small scale using weed matting, cardboard or newspaper to suppress the growth of plants by preventing them from capturing sunlight. This is useful for groundcovers, grasses and some succulents.

Solarisation uses the suns heat and black plastic cover to control invasive plants and reduce the seed bank in the soil. To solarise invasive plants cover them in thick black plastic and weigh it down on all sides or use pegs to keep the plastic down. The plastic will stop light reaching the plants which will stop them from being able to photosynthesise and will trap heat which will reduce the amount of seeds able to germinate in the soil. The process takes around 2 to 4 months depending on the weather. Factors such as rain and temperature will affect the success of solarisation. Solarisation is not usually effective for deep rooted plants as the soil temperature is usually only hot enough in the top couple of centimetres.

The splatter gun application method shoots a stream of herbicide with precision across a distance of around 8 to 10 metres. It is useful for forested or steep terrain where access limited and for the treatment of invasive shrubs like lantana. Council has splatter guns for hire.

Large vines, trees and shrubs can be stem injected. This involved drilling or cutting holes just beneath the bark to the sap wood of the plant around the stem 5cm apart and filling them with herbicide. The herbicide is transported throughout the plant and eventually kills it.

Wick wiping involves the application of herbicide by either a hand held or a rotating wick on a trailer, onto undesirable plants. The use of a trailer wick wiper is only appropriate for faster growing pasture weeds where a distance is able to be achieved between the invasive plants and desirable pasture species so that the wick only touches the invasive plants. A hand held wick wiper is useful for a variety of invasive plants including pasture weeds, ground covers and small shrubs. A hand held wick wiper allows a concentrated amount of herbicide to be wiped onto a plant. This technique is useful for pasture weeds. Council has both trailer and hand held wick wipers available for hire.

This method is useful for weedy vines and involves scraping off a section of the outer bark and applying herbicide within 15 seconds (any longer than 15 seconds will affect results). Wrapping plastic around the area where the herbicide has been applied can assist with the absorption of the chemical by the plant. The herbicide is transported throughout the plants vascular system killing it entirely. This method is useful for Madeira vine as it can easily regrow from stem fragments and therefore it is important to kill the whole plant.