G, R and T: three innocent letters that make up the acronym for one of the worst weeds in the State, Giant Rat’s Tail. GRT (Sporobolus natalensis) is currently a Class 2 declared weed in Queensland that causes significant amounts of damage to grazing lands and natural areas.
Originally from Africa, GRT was introduced to Australia for pasture evaluation. GRT spread through the contamination of pasture seed. Mature GRT leaf blades are tough, making it difficult and unpalatable for cattle to graze. In turn, this reduces animal feed intake and production. It also increases the pressure on other pasture species which in turn reduces competition which promotes further spread of GRT that degrades pastures.
In botanical terms, GRT is an erect, clumping and robust perennial grass that grows to a height of 1.7 metres. The leaf blades are flat or folded and linear from 25 to 50 cm long, whilst the width of the blade is approximately 2 to 4 mm wide. Basal leaf sheath margins are hairless. Seed heads are located on a spike that is 25-80 cm long and young seed heads are ‘rat tail’ shaped (hence the name), opening into a pyramid shape when mature with spikelets loosely spaced and fairly even. The seeds themselves are brown and incredibly tiny, 0.7 -0.8 x 0.4mm in size.
There are a range of GRT control options. Often the best results are obtained by combining a number of techniques including burning, chemical control (currently flupropanate or Glyphosate) and developing or maintaining vigorous, dense pastures. However management will depend on the size and density of the infestation, cost of control, access to the infestation, soil type and weather.
Reef Catchments encourages land managers to discuss with their neighbours best practices for GRT control. Any questions or comments? Head to the Reef Catchments Pest Management Forum and put up a post.