Introduction 

Noogoora Burr is a herbaceous daisy bush from Central America. It was accidentally introduced to Australia in the late 19th century, probably as contamination in cotton seed. It is found in all eastern mainland states, in the Kimberley region of Western Australia, in the Victoria River District and around Alice Springs. Although its potential distribution has not been determined, its current wide extent suggests that it could colonise most waterways in the Northern Territory.
The bristly fruits of Noogoora Burr are dispersed on animal fur and on clothing. Seed may remain dormant but viable for over a decade. Their ability to spread in floodwater has enabled the weed to establish along stream channels. Noogoora Burr also colonises disturbed ground.
Noogoora Burr needs full sunlight and an adequate moisture supply. It flourishes on rich soils, including black soil and alluvium, but can persist almost anywhere its sunlight and moisture requirements are met. It is toxic to livestock.

Impacts

Noogoora Burr forms dense thickets which exclude the majority of understorey plants. Due to the spread along water courses, wetland plant biodiversity is threatened by Noogoora Burr infestation. Noogoora Burr replaces the Cane Grass in which Purple-crowned Fairy-wrens nest. Fairy-wrens will feed in Noogoora Burr while its lush greenery provides shelter, but they avoid it once it shrivels and turns brown. If Noogoora Burr continues to spread, this weed could also affect a wider range of threatened species.
Noogoora Burr also has an impact on pastoral productivity. Due to its rapid growth rate and extensive root system, it competes with edible pasture species. If its seedlings are eaten, they are poisonous to most stock, and its fruits contaminate wool in sheep growing areas, increasing processing costs. Dense stands can also restrict stock access to watering points.

Noogoora Burr - Xantium strumarium

Photo: © Gabriel Crowley

Classification

Noogoora Burr is a declared weed in the Northern Territory and Western Australia. It is recognised as a significant environmental weed in the Northern Territory Parks and Conservation Masterplan and is listed as a high impact weed in the Field Guide to Assessing Australia’s Tropical Riparian Zones.

Control

Control practices recommended for Noogoora Burr include hand-hoeing to remove isolated plants; grazing of plants that are between seedling stage and flowering; and spraying young, actively growing plants. A number of chemicals are registered for control in the Northern Territory including 2,4-D, MCPA, metsulfuron-methyl, fluroxypyr, glyphosate, picloram and triclopyr. The recommended application of these chemicals is as a foliar spray.

Noogoora Burr - Xantium strumarium

Photo: © Gabriel Crowley Noogoora Burr takes over the vegetation along streams

In Western Australia, Noogoora Burr is one of the few weeds where quarantine restrictions have been used in an attempt to limit its spread. In the Kimberly, all pastoral leases from Fitzroy Crossing to the river mouth are quarantined in an attempt to prevent the spread of the weed.
Biological control has had mixed results. Until recently, insects released have had little effect on the species. A Puccinia rust reduced populations in eastern Australia, but has had little impact in the Northern Territory or Western Australia. However, Noogoora Burr is now reappearing in some of the northern Queensland rivers from which it has previously been largely eliminated by the rust. Investigations are underway into new strains of this rust that are adapted to northern climatic conditions.

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