Pasture dieback funding increase

MLA was awarded a $2.7m grant from the federal Department of Agriculture to help fund research and development, and has committed an additional $2.7m to match the grant funding with producer levy investment.

MLA general manager of research, development and adoption, Michael Crowley, said while recent widespread rain across many parts had transformed drought-hit pastures, it had also sparked a re-emergence of pasture dieback.

"Ongoing drought had made it difficult to tell the difference between pasture dieback and the impacts of drought. However, the widespread rain is starting to reveal the true extent of the problem," Mr Crowley said.

"MLA initiated a multi-pronged plan to address pasture dieback when it first emerged and we continue to work with a range of research providers, producer networks, the Queensland Department of Agriculture and Fisheries and NSW Department of Primary Industries, to capture and exchange information, and support producers to take action on-farm."

Part of the funding will be directed towards the investigation of pasture mealybug as a possible cause, led by Queensland University of Technology microbiologist Associate Professor Caroline Hauxwell.

Mr Crowley said while pasture mealybug was seen as a likely contributor to pasture dieback, it is vital the exact cause or causes are validated with certainty.

Dr Caroline Hauxwell's involvement in pasture dieback research began when she identified patterns in data collected from producers that were consistent with mealybugs.

"I was able to show people that the mealybugs are not just feeding above ground, but they're feeding below ground and we could find them consistently," she said.

"When you can't find them in the canopy, you can find them in the soil and on the roots around sick plants."

Dr Hauxwell was initially supplied with samples, then she moved to field work, including using a backhoe to dig 1 metre-deep trenches.

"We could find mealybugs overwintering on roots at about 900mm down, where they're getting in through cracks in the soil," she said.

"One of the reasons I think people don't find mealybugs as often as they could is that they can be very deep underground, particularly when it's cold and dry and they can get into the soil structure."

Collecting mealybugs from a wide area, Dr Hauxwell said Biosecurity Queensland identified them as Heliococcus summervillei - the same mealybug which was first observed causing severe dieback in paspalum in Queensland in 1926.

"We've also been digging up lots of healthy pasture... to look at mealybug numbers, but we've only been able to do this on a small scale because it's very labour intensive," Dr Hauxwell said.

"The MLA funding is letting us do much more detailed and widescale surveys now of mealybug, and particularly season-long monitoring at a number of sick sites so we can start to get a grip on what's happening to its biology.

"We're looking at different grass varieties that may be susceptible or not, and we're hoping to identify some more resistant varieties."

Dr Hauxwell said they're particularly interested in pastures that survive or recover.

"We're very open-minded to what producers are observing in the field because I think that... will be the key to finding the long-term solutions to this," she said.

"And that's why the MLA money is so important, because it lets us do work across the state and at scale with the number of people it takes to sort through and count and analyse soil and roots and grasses.

"We can do small-scale stuff only to a point; we need to do the bigger, expensive, labour-intensive stuff and that's what the MLA money is paying for and that should give them (producers) the peer reviewed papers that they're asking for."

Dr Hauxwell said she doesn't deny there could be other explanations for pasture dieback.

"But we think that the mealybug is a particularly important problem at the moment and it's responsible for a lot of the area that we're calling dieback."

Nutrien agronomist Josh Connolly, Biloela, said mealybug induced pasture dieback had become particularly problematic in the Callide and Dawson Valleys, with some producers losing up to 50 per cent of their pastures.

"The long-term effect of it is obviously the plant dies," he said.

"You might get another generation of plants from seedlings come through after another rain event, but they'll generally then be infected as well.

"You end up with this rundown of seedbank and then just this paddock of weeds growing.

"Weeds generally do their cycle and then die too, and then because you haven't got any great ground cover over your soil, that's when your soil starts to become hydrophobic and water starts to shed from it.

"It creates this really bad cycle in the soil for runoff and not allowing moisture into the dirt, which has long-term effects on production."

Despite conducting several trials on properties within the valleys, and seeing short and long-term success with insecticides, Mr Connolly said industry is still a long way off having any great recommendation to control it.

"The trouble with using an insecticide, mealybugs are quite susceptible to resistance or have the ability to build that resistance quite easily because they've got that waxy coating on them.

"There is some systemic pesticides out there which may work better, but they're very expensive."

Mr Connolly said a long term solution to control mealybugs could be endophytes, the naturally-occurring fungi that host within the plant and helps the plant deter the mealybug.