Fighting the flower: Solutions sought to eradicate invasive gazanias

Above-average rainfall across South Australia has led to one of the best cropping seasons on record, but it has also facilitated the spread of a notorious weed: gazanias. The plant, introduced from South Africa in the 1950s and 1970s as an ornamental garden plant, has become a declared weed in multiple states.

Researchers from La Trobe University have been conducting trials on farms in South Australia's Riverland and Eyre Peninsula to understand the pest plant's biology and how to control it. Project lead Ali Bajwa said, "Despite being so beautiful, [gazanias] cost us daily in terms of economic yield losses in grain production systems."

The Grains Research and Development Corporation (GRDC) has invested $700,000 into the three-year project. Earlier work revealed the extensive spread of the weed across southern Australia and parts of Western Australia. Dr Bajwa said the best results in managing gazanias had been a combination of cultivation and spraying herbicide mixtures.

"While cultivation is not desirable in these soil types and the sort of erosion risk or other environmental factors that can come with that, if we use it strategically once in a while that can potentially be a good option," he said. Dr Bajwa added that up to 95 per cent of gazanias could be wiped out in paddocks using cultivation and sprays.

La Trobe University scientist Ali Bajwa and Hoang TN Nguyen visited trial sites to see the latest results. Dr Bajwa said there was no registered product to control gazanias, with farmers using a mixture of herbicides to fight them. "We're getting some very good results and hopefully within [the] next year or two we could be potentially seeing some minor use permits or potential registrations for this particular weed," he said.

Paul Rudiger, a farmer from Loxton, has been battling gazanias at his farm for decades. The weeds have rendered some of his paddocks unviable for cropping. "The crop, the cereal we sow around them will actually die because with their [the gazanias'] root system they take all the moisture," he said.

While cultivation was intensive on the land and expensive to perform, Mr Rudiger said it was controlling the pest weeds enough to allow his crop to grow. "It's a cost and something that we would rather not do but because we can kill a gazania I'm happy to see a dead gazania," he said.

Paul Kaesler, another local farmer, is also using cultivation and sprays to get rid of gazanias at his farm. He expressed concern that approvals for new herbicides are taking too long. "I think that needs to speed up in some way or another or else they will be across the whole state before everyone knows," he said.

Mr Kaesler emphasized the importance of adhering to restrictions banning the sale and movement of gazanias in South Australia. "We still have people come through and go, 'Oh, I'm going to put them in my garden,'" Mr Kaesler said. "Yes, they look pretty and wonderful but they're more of a pest than they are a prettiness."