Sugar trial update

Council began a trial using sugar to suppress weed growth in 2020, which was detailed in the Autumn 2021 newsletter. Even with the wet summer weather being perfect for weed growth, staff have found that weed growth is still supressed without needing follow up treatments.

Demonstrated through the success of the Wattle Grove trial, staff were keen to test the viability of this control method across a variety of different sites and conditions. Council’s Bush Regeneration staff expanded the trial to additional sites including:

• Lake Francis, Carnes Hill; • Lake Moore, Chipping Norton; • Light Horse Park, Liverpool; • Haigh Park, Moorebank; • Amalfi Park, Liverpool; • Cessna Reserve, Middleton Grange; and • Kelso Reserve, Moorebank.

Additional areas were selected due to the high numbers of Farmer’s Friend (Bidens pilosa) which was the focus of the original trial. These sites provided an opportunity to test how well the sugar treatment performs in other conditions and its effect on other weeds.

Council staff and volunteers were keen to test how well the sugar treatment would work in a natural bushland setting with native vegetation, in comparison to the landscaped Wattle Grove site. These new sites were not mulched as part of the trial, as this would prevent the native plants from growing too.

It was also important to see how effective the use of herbicide was in preparing sites for sugar treatment. A few plots were tested by spraying the weeds and in other plots the weeds were removed by hand. Spraying was only found to be effective in plots that were also mulched. Tests of the sugar treatment across a small area were set up to see whether sugar would help control succulents, specifically Mother-of-Millions (Bryophyllum species). While it appeared successful after two treatments, a larger plot is being tested to eliminate other contributing factors.

Given Liverpool is a flood-prone area, it was important to check if the sugar treatment would work in riparian areas where the influence of water favours weed growth, due to additional nutrients and weed propagules. Test plots at Lake Moore are proving successful, even after the floods covered the site with a layer of sediment. Unfortunately, the plots at Kelso Park have been inaccessible through the wet weather and will require further monitoring.

The sugar treatment continues to prove successful, both in landscaped areas and bushland settings. The bush regeneration team will continue expanding the area treated with sugar. This will allow the team to spend more time treating more invasive species when visiting sites rather than maintaining aesthetic bushland edges. As the trial continues, this treatment is proving to have lasting benefits.

Mother-of-millions, Bryophyllum delagoense leaflets. Image courtesy of John Hosking/DPE

Site covered in weeds before the sugar trial Spreading the sugar after hand weeding the site The site is clear of weeds six months later

Propagules: Any part of the plant that can become detached and give rise to a new plant, such as seeds.

A riparian area or zone is land alongside creeks, streams, gullies, rivers and wetlands. These areas are unique and diverse and are often the most fertile parts of the landscape. Amalfi Park, Cessna Reserve and Light Horse Park were all initiated at the request of Council’s incredible Environment Volunteers who wanted to try out the sugar treatment themselves. This technique has been safe and easy, making it perfect to incorporate into volunteer activities. Sugar treatment has benefitted sites where the opportunities to manage weeds were limited, for instance during the COVID-19 pandemic.