Sedge saga:  Government must act now to reduce spread of invasive Navua sedge

2 July 2024

A crisis is unfolding across many North Queensland regions as the invasive weed Navua sedge (Cyperus aromaticus) continues its relentless spread across prime agricultural lands and recreational grounds and facilities.

The aggressive weed has shown a remarkable ability to adapt and proliferate in our tropical climate, outcompeting native flora and reducing the productivity of pastures and crops such as sugar cane.

Queensland Cane and Renewables (QCAR) Senior Technical Officer, Mr Lawrence Di Bella said that the highly invasive nature of Navua sedge meant it was having a negative impact on grazing and agriculture lands, but also land used for community activities and the environment in general.

“Navua sedge is aggressive in that it displaces other plants including natives, and it can disrupt machinery operations and productivity in both agricultural and grazing systems,” Mr Di Bella said.

“The spread is increasing rapidly through North Queensland and it’s becoming a significant problem in the cane industry where it can stall base cutters on harvesters and negatively impact the overall yield of a crop.

“In land used for grazing, the weed out competes other plant species and I’m aware of productivity being reduced by as much as 60 to 70 per cent in some instances.

“Currently there is only one chemical that is approved for use in and around crops but it only targets Navua sedge seedlings and not the well-established weeds. Additionally, a number of primary producers have implemented no slash zones especially when adjacent to roadsides and are attempting to control it in areas outside of cropping by the use of herbicide.

“We would like to see an integrated weed management program implemented across the landscape utilising biological, chemical and cultivation control measures as well as exclusion strategies to minimize further spread of the weed. Any biological controls would need to be monitored to ensure no negative impacts extended to other plants or crops.”

Adrienne Kelley of the Herbert River Pony Club, said that Navua sedge had all but taken over the main arena and nearby paddocks of the pony club putting their competition and club at risk.

“Because of the large and uneven clumps the weed makes, it is making our arena unsafe for riders,” Ms Kelley said.

“North of Rockhampton, Herbert River is the only location where a State Level Cross Country Championship has been held in the past 20 years. If we lose our cross country course we would miss out on bringing such an important event to Ingham simply because of a weed that can’t be controlled.

“Due to the way the sedge lifts the dirt up, we’ve lost 20 centimetres of height on some of our jumps and what used to take a couple of hours to maintain, is now taking days to.”

Hinchinbrook MP and Katter’s Australian Party (KAP) Deputy Leader Nick Dametto said that he regularly spoke with concerned stakeholders across the Herbert region who are in desperate need of more chemical and biological options to try and curb the spread.

“Slashing and mowing has seen Navua sedge spread around our district like wildfire. That’s why in addition to biological and herbicide options, we must really see an exclusion strategy implemented across all sectors,” Mr Dametto said.

“The Government plays a crucial role in addressing this crisis and must continue to allocate resources and funding towards research aimed at finding affordable solutions.

“My last Question on Notice to the Minister for Agricultural Industry Development and Fisheries raised more questions than answers about what research has been undertaken.[1]

“The Minister made specific reference to a rust pathogen that has been detected in the Atherton Tablelands and was killing sedge but then indicated that no further rust fungus research would be conducted.

“It makes no sense that research into rust fungus would be ceased. Provided there are no negative side effects to other plant species, it might be the strong biological solution that is very desperately needed.

“I have written to the Minister seeking clarification around what research is continuing. We must create a multifaceted approach before this weed reaches the point of being uncontrolled by any measures. It’s not only the broader agricultural sector that relies on finding a solution, but our community clubs and the environment in general. We don’t want our native lands to succumb to this aggressive weed.”

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[1] https://documents.parliament.qld.gov.au/tableoffice/questionsanswers/2024/579-2024.pdf