Australia — A native weed, which has thrived after a major bushfire in western New South Wales last year, has started killing hundreds of livestock due to its addictive nature.
The legume Darling Pea has flourished since the bushfire last January, which burnt 53,000 hectares of the Warrumbungle National Park and farms at Coonabarabran.
So far more than 800 sheep have died on one property alone and landholders fear the death toll will rise.
The Darling Pea had little competition because the fire wiped out other weeds and pasture.
Coonabarabran farmer Tony Knight lost more than 200 sheep and hundreds of hectares of pastures in the bushfire. Shortly after the blaze, the Darling Pea took hold.
“Next thing, it’s a metre high and all over the place and it’s starting to get very toxic,” Mr Knight said.
He says preventing the sheep from grazing the addictive weed was almost impossible because the bushfire had destroyed kilometres of fencing.
“At the time that the sheep were getting poisoned we had a lot of things on our mind,” he said.
“We’d had the effects of the fire, trying to get everything back to normal and the pea was a real problem when it was starting to get dry and it just became one of our problems.
“It would have been nice if we could have spent more time with them, if we could have mustered them more, taken the affected ones out and put them on a paddock that had no pea.”
Darling Pea toxins affects enzymes in brain
Darling Pea, or Swainsona, can be found throughout Australia and is usually found growing on farms.
Coonabarabran weeds inspector John Unwin says the problem was caused by the unique chain of events which unfolded after the fire.
“The Darling Pea, being a native, is used to fire and most Australian natives are quite used to fire,” he said.
“There’s no competition and on top of a rather large bushfire we’ve got a drought.”
Autopsies were carried out on some of Mr Knight’s sheep and the results returned positive for Swainsona poisoning.
Regional veterinarian Greg McCann says the toxins in the pea affect an animal’s brain by attacking an enzyme involved in metabolism.
“They lose the ability to judge where their feet are. They become wonky, fall over, appear to be blind, walking into things,” he said.
“They can assume funny postures, like head bent down or head bent back, but the one thing that was seen in the cases associated in the Coonabarabran area were twitching.”
Stephen Lill is another farmer in the Coonabarabran district who has had problems with Darling Pea. He says the weed has grown extensively in his rugged terrain.
“The weeds that came after the fire were quite a different pattern,” he said.
“Usually weed infestation happens gradually and you have options to adopt.
“Whether it’s moving sheep or cattle off that area and letting the weeds go through their poisonous stage and then re-introducing them but this year we didn’t have the options because of the fire and no feed.”
Farmers hope rain will speed recovery process
The New South Wales Local Land Services says five of the 15 varieties of Darling Pea are listed as vulnerable or endangered.
A landholder may need approval under the Native Vegetation Act for any control programs and these are determined on a case-by-case basis.
Rotating livestock is considered the most effective way of controlling the effects of the pea, but farmers like Mr Knight did not have this option because of the bushfire.
“It just made it so hard,” Mr Knight said.
“We pretty much had to drop everything and get these fences up to have any sort of control over them at all.”
The Coonabarabran district has now received widespread rain which farmers hope will help speed up the recovery process.
“More suitable pasture would certainly help,” Mr Knight said.
“More suitable pasture on land that doesn’t have the pea so that we can take the sheep down and get them off it. That’s about the only thing that we can do.
“You wouldn’t dream that it would happen like that. We just feel that we’ve had our share of bad luck.