Drone trial up and away

The use of drones to spray invasive weeds took flight this month as a means to control the invasive Hymenachne weed on Cape York. 

Cape York NRM in partnership with Queensland Parks and Wildlife Services, trialled the operation at Rinyirru National Park, where known outbreaks of Hymenachne are the target of a   broader Southern Cape York Hymenachne Control Project.

The project, which runs until March next year, aims to protect high-value wetlands of Cape Melville and Rinyirru National Parks by aerial and ground control of Hymenachne, as well as implementing a monitoring and survey regime to enable early detection of new infestations. 

“This is the first time we have used drones for weed control work on Cape York,” QPWS Senior Ranger Dan Mead said. “To date we are unaware of anyone else using this technology on the Cape but it will have great application for many scenarios moving forward.”

The week-long trial began at sites where it was easy to observe how it worked, with staff from  Rinyirru (Lakefield) Land Trust present to assess the method. The group then sent the drone into more inaccessible areas. 

“Generally, the overall operation was very efficient to execute, however, we were using an experienced contractor,” Dan said. “In the not too distant future I can see land holding bodies utilising this technology themselves, but for now I suggest small partnerships between neighbours and other stakeholders to engage a suitable contractor.”

Hymenachne is a semi-aquatic grass that was introduced into Australia as grazing fodder in ponded pastures in the late 1970s and in tropical wetlands of northern Queensland in the late 80s. Within a decade it had spread and is now a Weed of National Significance.

It invades permanent water bodies and wetlands; blocks waterways, potentially causing flooding and threatening drinking water; forms dense stands that reduce plant diversity and available habitat for native animals; and can also affect water quality. 

Control of the weed is carried out using repeated doses of herbicides through helicopter sprays and on-ground management such as burning before flooding, but it can be costly and difficult. 

Cape York NRM’s Coastal Ecosystems Coordinator, David Preece said the introduction of new, adaptable technology was part of the ongoing refining of methods to survey and manage weeds such as Hymenachne.

“Using drones offers another method, one which may provide more flexibility given they are quick to deploy and refill, smaller and able to fly lower. It is also very easy to adjust settings such as speed and flow rates, etc,” Dave said. 

“I don’t see the drone completely replacing the other control techniques we have been using, however, it will certainly complement them and help increase efficiencies in weed control.”

The Southern Cape York Hymenachne Control Project is supported by the Federal Government’s Reef Trust 7 Catchments to Coral program.