Rat's tail grass on the march

Rat's tail Grass infestation at Twin Hills, Finnis River Catchment

[Link to further information added 18 April. Click here.]

A pastoralist recently estimated that exotic Rat’s Tail Grass (Sporobolus species) has invaded 300km² in the Finnis River Catchment.  Smaller outbreaks have been found in the Douglas Daly and Adelaide River catchments, but a lack of awareness suggests it may be more common there too.

There are three species of rat’s tail grass. The plant known as American Rat’s Tail or wire grass (Sporobolus jacquemontii) is the common variety and it tends to be shorter (0.5-1m) than the less common Giant Rat’s Tail grass.

It is described as a prolific seeder with high seed viability and relatively unpalatable to stock and it will apparently wear their teeth out. The seed head is 8 - 25cm long and leaves 3mm wide. Its seed life is about 8 years.

Colin and Calvin Deveraux from Twin Hills Station told me about their fight with rat’s tail grass.

“Rats tail grass has invaded Twin Hills over the last 6-8 years.  From odd plants, I think we must be up to 5-6 km².

“Dew in the dry season helps the tiny seeds stick to everything. Unless a place is occupied by a competitive plant it will get a hold. It’s very hard to control.

 “The only way you can identify it is by its seed head (see images below) so it’s already lost some seed when you kill it.

“We started pulling it. You think you’ve done a good job and the next year you come back and it’s thicker and there’s another 8 spots.

“Burning helps it spread (and doesn’t kill plants). Slashing won’t kill it. It’s very hard to hand pull and there’s not much chemical specific to the plant. The only way you can treat it is to boom spray everything with Round Up.

“Flupropanate (selective) is recommended by Queensland but it will take six months to kill it. We used some and it hasn’t worked. It probably needs to be researched under our conditions.”

Flupropanate may be less effective in high rainfall and sandy soils. This chemical requires a four month withholding period after broad scale application.

Fertiliser is also recommended on improved pastures as the grass seems to thrive in nutrient depleted soils.

“We’ve got Mimosa here and maintain areas that we’ve recovered, so that’s our priority. We tried to hold rat’s tail but I think it’s beaten us.”

Early detection, competitive ground cover and spread reduction are essential.

If you have seen it or have it on your property on Peter Clifton on 0419 142 835.