What is the weed problem?
Wandering trad (Tradescantia fluminensis) is a herbaceous groundcover plant native to South America that has become a significant environmental weed of temperate Australia, with hotspots in moist forests of eastern NSW, south east Queensland and Dandenong Ranges region of Victoria. It forms dense swathes along the forest floor, particularly in moist riparian zones, where it reduces the diversity of native vegetation and alters the movement and behaviour of native animals. Wandering trad can also cause skin irritations to domestic pets, thereby reducing the recreational amenity of hikers and dog walkers using public pathways through infested forests.
Wandering trad primarily spreads via stem sections by water movement along creeks, soil disturbance and in dumped garden waste, meaning that it does not rely upon pollination and seed production for spread.
How is the weed currently managed?
For small infestations, manual removal of wandering trad is the most suitable option for control, but it may cause disturbance to the soil profile and stimulate germination of other weed species. Wandering trad can regenerate rapidly from broken stem and root fragments, meaning that hand-pulling is ineffective in the long term unless all material is removed from a site. For large infestations, chemical control is considered more practical, although there is potential for non-target damage to native plants growing alongside wandering trad. Herbicide application is particularly problematic along creek lines in the presence of threatened native vegetation. There is increasing evidence that wandering trad can regenerate after primary chemical control, leading to the need for multiple follow-up herbicide treatments, which is considerably costly.
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What can biocontrol offer to the weed’s management?
Classical biological control is the only recognised sustainable solution to the suppression (but not eradication) of environmental weeds to reduce their impacts at a landscape scale in Australia. Use of mechanical or chemical control for wandering trad in sensitive rainforest settings, especially along creek lines comprising endangered plant species, is unviable over large spatial scales, because wandering trad can routinely regenerate unless long term intervention is undertaken. A biocontrol approach may offer a longer term, sustainable solution to controlling wandering trad in sensitive ecological communities with lower risks to native vegetation.