Recent research has confirmed the culprit behind pasture die back syndrome - a Queensland bug that has blown across the Tweed and Kyogle border, heading south on the wind with the potential to affect all tropical grasses in the state.
As suspected for a long time the causal agent is pasture mealybug, Heliococcus summervillei first blamed for the problem in Queensland in 1926 and more recently in New Caledonia and now in Barbados and Puerto Rico.
While there is registered chemistry to combat the problem in emergency situations, researchers are shying away from the big- guns-blazing approach in favour of a measured and older response - in the form of paddock improvement followed by mob grazing.
If it all sounds rather regenerative, well you're right. The techniques adopted by successful graziers in curtailing the problem have hinged on some basic principals regarding soil health.
Research was carried out on 40 sites from Northern NSW to the central highlands of Queensland by Dr Caroline Hauxwell and her team at Queensland University of Technology, in conjunction with Queensland Biosecurity. The project was funded by the MLA.
"There's a significant correlation between the number of mealybugs present in a pasture and the severity of dieback symptoms in a range of grass species," she said.
"We can reproduce the symptoms by infesting grasses with the mealybugs, and grasses recover if treated with systemic insecticides.
"We think that the mealybug weakens grass, making it less productive and vulnerable to infection, and in the right conditions (such as after rain) multiple grass pathogens pile in and kill it.
Paspalum is the victim in this game, while legumes are the winners along with perennial ryegrass. Brassicas also do well in bringing back a paddock from the dead, as does sorghum.
Dr Hauxwell found rye inoculated with endophytes were well prepared to fightback dieback - so long as the plant was not allowed to grow tall and rank.
The practice of keeping a body of feed for later on is being challenged by this new work with Dr Hauxwell saying graziers need to think like farmers when it comes to managing grass for production.
"Sites with severe die-back had very little beneficial fungi in their soil," she said. "In grass paddocks with limited species die back ripped right through. So we need to develop a more diverse paddock."
Legumes, for instance have a nice relationship with fungi and are not affected by die-back.
"Mealy bugs don't attack these plants and they provide good fodder," she said.
One property near Biloela, Qld experimented with spraying out affected pasture and oversowing with non-irrigated lucerne, clover and desmanthus where they suited.
In Northern NSW cowpeas and lab lab both provide high protein fodder and will help replace pasture after die back.
Central Queensland graziers found that sowing panic grass responded very well and in one case bottom line profit, based on cattle weight, increased 10 fold as better managed pasture came on line.
Key to success involved close cropping of pasture by mob grazing in a rotational setting, or by slashing with the aim being to remove biomass where the mealy bug will breed. The added benefit is reduced fire risk.
"Graziers need to manage for productive foliage, not biomass," Dr Hauxwell said.
"We expect the smart, early adopters will embrace active management rather than just opening the gate. We want them to work towards managing their paddocks for maximum impact.
"All these ideas are already here and incidentally, the result is an improvement to your bottom line."
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