Cutch tree causes economic damage by forming dense impenetrable stands. It can potentially reduce primary production by displacing and/or shading pastures. The sharp thorns on cutch tree branches can impede the movement and mustering of stock.
Cutch tree is found throughout the Indian subcontinent, including Assam and Myanmar (Burma), as far as the lower Himalayan ranges and Afghanistan. It also occurs in some parts of Indonesia, where it has apparently been planted as an ornamental.
So far, cutch tree has only been found in Darwin in the Northern Territory. It spread from the Darwin Botanic Gardens to the nearby Darwin High School. Control of these two infestations was initiated in the 1980s, and is ongoing to ensure that cutch tree is completely eradicated.
Cutch tree reproduces by seed. Mature trees produce large numbers of seeds, which can be transported from the parent tree by cattle. The seeds remain viable even after passing through the digestive tract, and can be spread large distances in this way. Seeds can also be spread by the actions of water and people, or in mud sticking to animals or machinery.
Cutch tree is a small tree, growing 3–15 m high. The stem is dark brown to black, with rough bark which peels off in long strips in mature trees; young trees have corky bark.
The fern-like leaves are 100–200 mm long and contain between 8 and 30 pairs of small leaves made up of numerous, oblong pairs of secondary leaflets 2–6 mm long. Glands occur on the stem below the first pair of leaves, and between the uppermost six pairs of leaves. Pairs of stout thorns up to 10 mm long are found at the base of each leaf.
The flowers are white or pale yellow, each about 3 mm long. Flowers are bunched tightly together to form a flower spike, 35–75 mm long, resembling a lamb’s tail.
The brown, beaked seed pods are 50–125 mm long on a short stalk and contain between four and seven seeds, which are dark brown, flat and 5–8 mm in diameter.
The taproot branches to 2 m depth.
Cutch tree prefers subtropical or tropical open woodlands and grasslands. It grows well on most soils, but well-drained, shallow to medium-depth sandy soils suit it best. In its native range cutch tree has the tendency to invade degraded areas, eg overgrazed grasslands. Regular burning is also conducive to its spread.
CRC for Australian Weed Management: Ian Miller (NT DBIRD), Andrew Mitchell (AQIS/Weeds CRC), Blair Grace (NT DIPE/ Weeds CRC), Sharon Wilson (NT Botanic Gardens) and John Thorp (National Weeds Management Facilitator).
Because there are relatively few cutch tree infestations, and it can potentially be eradicated before it becomes established, any new outbreaks should be reported immediately to your local council weed officer. Do not try to control cutch tree without their expert assistance. Control effort that is poorly performed or not followed up can actually help spread the weed and worsen the problem.
Mature trees can be controlled with herbicides
Mature cutch trees can be killed with herbicide applied by basal bark spraying, stem injection or the cut-stump method. In basal bark spraying the herbicide is sprayed around the entire circumference of the stem from the soil level to a minimum of 300 mm height. The herbicide must soak into the bark and therefore be sprayed liberally until it runs off the bark. In stem injection herbicides are applied immediately (ie within ten seconds) after either drilling or cutting holes around the circumference of the stem. In the cut-stump technique the tree is cut as close to the soil as possible and then similarly quickly painted with herbicide. Cutch tree will reshoot readily from a cut stump, so simply removing the stem without herbicide application will not kill it. All of these techniques allow the herbicide to be transported to the root systems and ultimately cause death. Note that although herbicides are most effective when plants are actively growing (ie the wet season for cutch tree), the basal bark technique is least effective when the bark is wet.
Seedlings can be easily removed by hand or with herbicides if numerous
Seedling cutch trees can be removed byphysical or chemical means. If there are large numbers of seedlings, herbicides applied by spraying the entire plant may be the most time- and cost-effective technique. Otherwise, isolated occurrences of small seedlings can be removed by hand if the soil is moist, or can be grubbed out using a mattock, ensuring that as much root material as possible is also removed.
Follow-up control proceduresare crucial
Once the infestation is initially controlled, follow-up monitoring and treatment should be undertaken at least three times each year. In particular, attention should be paid to re-treating any regrowth from mature trees and removing seedlings that have germinated from the seedbank. Because seeds can remain viable for such a long time, it is important to continue follow-up control for up to 20 years after the last seed drop.
Cutch tree (Acacia catechu) is not declared in NSW under the Noxious Weeds Act 1993.