Weed Control
The bulk of our efforts and resources are spent on weed removal and control. Removal by hand and by hand-spraying are the most common. Fire can also be used a control agent.

People involved include contractors (including abseilers), volunteers, mutual obligation workers, council employees, and NPWS staff.

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Cut-and-Paint
Physical Removal. is viable for smaller plants up to about 12cm tall: they can be pulled by hand, especially after rain.

For larger plants, cut-and-paint may be the best method. Simple hand tools are used. The stem is cut with loppers as close to the ground as possible, then immediately painted with a herbicide such as glyphosate. This method is slower than spraying but very effective in areas where the bitou is closely mingled with native plants which are to be protected.

Click here to see a video on "Design for a Bushcare Kit".


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Alan & Splatter Gun
Herbicides are usually applied by either contractors, or appropriately qualified members of SWRDC, using a "Splatter Gun" - a pressurised pack with a spray gun. An effective range of some 12 metres allows a worker to cover up to ten times more area in a day than the cut-and-paint approach.

The Splatter Gun is both accurate and effective. It allows bitou bushes to be targetted with little or no negative impact on adjacent native vegetation.

SWRDC started using the Splatter Gun in about 2009 and it is a really great addition to our arsenal.

Herbicides used include Glyphosate and Metsulfuron. Both are diluted with water. the concentration depending on the season and the weed species being treated.


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Leaf Roller Moth
Damaged Leaf
Bitou Biological Control began in 1987. There have been three agents that have had some success. In general these controls have formed a useful addition to other methods, as they require no labour for their effect. Unfortunately, all so far have had their effectiveness reduced by predation, drought, and other factors still under investigation.

The most useful to date is the the leaf-rolling moth, Tortrix sp., Eggs and larvae were released in 2001. The larvae are mobile and feed on young shoots. The insect is most active in summer and may defoliate, weaken and kill the plant. Picture at left shows an eaten-out bitou tip showing the characteristic silky appearance. Subject to predation which can weaken the effectiveness of this moth.

Another moth, the bitou bush tip moth, feeds in bitou stem tips destroying developing leaves, buds and flowers and reducing seed production. It is now widely established in [website] the field but does suffer heavy predation and parasitism at some sites.

Thirdly, the bitou bush seed fly is now widely established. The larvae feed on developing seed, causing major reduction in seed production.

Field trials are underway for a rust that affects boneseed (and the closely related bitou bush).


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Lantana Biological Control holds out the best hope for long-term control in many cases - since it can be both safe and economic. Since 1914, about thirty agents have been introduced to try to control the weed. Seventeen have become established: eight are widely distributed: and four are causing substantial damage. Most of the agents attack the leaves, but others attack flowers and seeds, or suck the sap.

The four are two beetles, the Lace Bug (Teleonemia scrupulosa) and Leaf Beetle (Octotoma scabripennis), and the Leaf Miner (Uroplata girardi), with a Seed Fly (Ophiomyia lantanae). Pictures of the first three are shown at the left

One problem is that lantana thrives in many diverse conditions, whereas some agents can only exist in a limited range. Also, lantana can withstand extended periods of drought by dropping leaves to conserve water. Therefore many of the leaf feeders are unable to maintain high enough populations to cause significant damage. Thirdly, since there are many lantana varieties, it turns out that some agents prefer some varieties and are of limited use in attacking others.

The search for further agents is under way at the Institute for Biological Control in the UK.


rust spray

rust leaf

Rust Spraying, with sprayed leaf.
Lantana Leaf Rust prospodium tuberculatum was the first biocontrol agent for lantana used in Australia: it was released in 2001.

The rust attacks the leaves, producing little blisters on the undersides. It works best in sites where the temperature is mild and where there is dew or light rain. The rust can reproduce quickly, completing its life cycle in as little as three weeks.

Rust populations are self-sustaining, as the spores can survive dry winters. In suitable moist conditions the lantana bush can be extensively defoliated.


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A Bitou burn-off
Fire.

Bitou has high moisture levels therefore high burn temperatures are needed. This is bad for native plants that have evolved to cope with more frequent low-intensity fires. Subsequent regeneration means extensive follow-up.

We have not used (intentionally) this method at SWR - it could be suited as an initial strategy if there were committed resouces available for follow-up for several years.


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Helicopter
Mass Spraying.

May be applicable for heavily infested areas where there are few native plants left, and where there are large areas. Expensive.