Managing giant rat’s tail grass

Managing Sporobolus species and other weedy grasses in pasture: learning the latest
from Florida with Brent Sellers (Pasture weed specialist), webinar recording (25 minutes).

Ten things we can do to manage giant rat’s tail grass

Giant rat’s tail grass (GRT) is an invasive grass that can reduce pasture productivity, out-compete desirable pasture grasses and cause significant degradation of natural areas. It is often referred to as a weedy Sporobolus grass. Weedy Sporobolus grasses have low palatability when mature, are difficult to control and can quickly dominate a pasture, especially following overgrazing or soil disturbance. They can affect cattle health and productivity, including finishing times, weaning percentages and weights.

While there is still no silver bullet for GRT, ten things we can do to manage it are:

  1. Get suspected GRT grass positively identified by sending plant samples to the Queensland Herbarium. It can be difficult to pick introduced GRT species from native GRT species, and nearly impossible to distinguish between the introduced GRT species.
  2. Control isolated plants and stop seeding. Preventing GRT infestation costs far less than ongoing GRT control.
  3. Contain the spread of GRT by making 10 to 20 metre buffers along roadways, waterways and inside property boundaries. Always practice property, vehicle and equipment weed hygiene. Avoid moving through GRT areas when seeds are sticky, after rain or heavy dew. Only use reliable sources of fodder, pasture seed and equipment hire.
  4. Apply the correct calibrated dose of flupropanate for effective GRT control — 1.5 grams per square metre for granular and 2 millilitres per litre for liquid flupropanate. Too much will kill surrounding competitive pasture grass. Too little will not kill GRT tussocks.
  5. When spot spraying with glyphosate at a rate of 20ml per litre, trickle it down into the centre of the GRT tussock to prevent damaging nearby beneficial, competitive pasture grass. Wick wiping can selectively apply herbicide to GRT with minimal damage to nearby beneficial pasture species.
  6. Abide by grazing withholding periods when applying herbicides. Fourteen days for spot spraying and four months for broadacre or aerially applied flupropanate. Slaughter and milking withholding periods are 14 days on clean feed after grazing in a flupropanate-treated paddock. Check herbicide labels for withholding periods for lactating cows and goats. Glyphosate has no withholding period.
  7. Budget for ongoing GRT follow up for many years. The residual activity of flupropanate treated areas lasts two to three years, whereas GRT seed lives for more than eight years.
  8. Quarantine cattle for seven days to prevent the spread of GRT seed into clean areas.
  9. Promote pasture competition to control GRT. Pasture grasses with runners are more effective than tussock grasses in outcompeting GRT. Be aware of plant-back periods for certain improved pasture seeds after applying flupropanate herbicide.
  10. For cost effectiveness consider the option of cultivating and forage cropping for three years in suitable areas of arable land infested with dense GRT.

Adapted from Marie Vitelli’s article in the September 2017 edition of AgForce’s ENVOY magazine.

Where to get more information about and help with identifying and managing GRT

Download a copy of the Queensland Herbariums step-by-step guide to collecting, preserving and submitting plant specimens for identification at the Business Queensland How to identify specimens web page.

The Rat’s tail grasses: Sporobolus pyramidalis, S. natalensis, S. jacquemontii and S. fertilis fact sheet (PDF, 9.27 MB) (by Biosecurity Queensland) summarises the legal requirements, description, distribution, control and management strategies for weedy Sporobolus grasses in Queensland.

The aim of the Reducing weed risks from fodder (PDF, 10.2 MB) guide (by the Queensland Herbarium) is to increase awareness of weed risks associated with fodder use in Queensland. It highlights tools and strategies to help assess weed risks when sourcing fodder and how to reduce week risk when transporting, storing and feeding out fodder.

More general and related information about giant rat’s tail grass is available from Business Queensland and NSW WeedWise.

The Weed Spotters’ Network Queensland aims to find, identify and document new occurrences of potential weeds to allow prevention and early intervention. It manages a community-based weed alert system, produces a monthly weed spotters’ bulletin and has resources to help with weed identification.