A leaf fungus has been released along the edges of the Bega River to control an invasive weed called the wandering trad.
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The CSIRO are currently conducting a widescale release of the fungus to control the viability of the weed in NSW with funding from the Environmental Trust.
Wandering trad is a semi-succulent groundcover native to South America and was introduced as an ornamental plant. It is a highly competitive weed that takes over the ground cover and often smothers the undergrowth of vulnerable native forests.
The biocontrol fungus was discovered by researchers in Brazil. When infected the leaves develop lesions that cause the leaves to die. It helps to reduce the overall foliage and the ability for the plant to photosynthesise and therefore reproduce.
CSIRO research scientist Dr Ben Gooden met with Bega River and Wetlands Landcare Group (BRAWL) on Monday, May 24, to demonstrate how the fungus would be released into the environment. He also explained the research being conducted about the spread of the fungus in other parts of the country which will be modelled for its release on the Bega River.
Dr Gooden collected samples of infected leaves from the Brogo River where his team have been conducting controlled spread of the fungus to show the group how the infection occurs on the leaves.
"Over time the leaf that is infected will die. That leaf will then produce fungal spores that then move on to another leaf."
The spread of the fungus is slow and in temperate climates like the Bega Valley, infection of the surrounding plants will likely take between three to six months. Significant reduction of the invasive ground cover will likely around two years.
"It will be a slow and sustained infection, leading to a reduction of trad in the long run," said Dr Gooden.
According to extensive research conducted by the CSIRO, native plants are unlikely to be affected by the release of the fungus. Studies found that even in optimal conditions, the fungus is unable to grow on native species.
The impact on native species is likely to be very positive due to the reduced competition for ground cover and nutrients.
BRAWL community coordinator Erin Moon has been with the group for three years and has a background in environmental science.
She coordinated the release efforts with Dr Gooden and instructed volunteers on how to release the stems with infected leaves into large patches of trad.
The release was quite simple. Three infected stems were placed into a patch using a thin piece of bamboo to create a hole to plant and release the specimen.
"Hopefully this tips the balance on some of our successes down here and means we can focus on other things and we can forget about the trad. It's good if it can take one weed off your to do list," she said.
Community groups like Landcare or Bushcare have been invited to conduct coordinated releases of the fungus to assist the project.
The fungus is provided to these community groups at regular intervals from September 2020 until June 2023 depending on climatic conditions, quality of the infected specimens and demand from registered groups.
"Hopefully once we start seeing a bit of a dieback of the trad then we can start focusing on the ground cover a bit more. The Lomandra is the only one we really put in to the ground cover because it will grow even when it's completely swamped by trad."
With each flooding rain, trad grows back even stronger along the Bega River bank and continues to threaten native regeneration.
Volunteers from BRAWL participated in a vegetation clean-up and helped to clear trad from some of the native trees and plants they previously planted as well as try to eradicate any new invasive species.
A rogue willow tree was one such species which had somehow found its way to a spot on the banks which was removed and cleared from the area.
Coralie Frew and her husband Keith have been volunteers for BRAWL for about three years.
"We used to ride our pushbikes along here and think what a wonderful job they were doing and if people are doing something wonderful like this for your community you want to show your support."
"One of the issues I think Erin has is that the people doing it are all an older group, so we do tend to tire, but we just say to ourselves do a patch at a time and keep going.
"It's looking great here, it would be good to look at a before and after photo because you sometimes don't notice what has actually improved."
READ MORE: Bega's bamboo forest has been removed
BRAWL is a voluntary, community organisation that monitors, plans for and implements activities relating to Bega's rivers and wetlands. The group began in 2006 and works in cooperation with the Southern Rivers Catchment Management Authority and the Bega Valley Shire Council.