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Roadside slashing a good option in addressing weeds

Feathertop Rhodes grass has a highly mobile seed that can spread from roadside verges to paddocks.
Photo: CSIRO

Addressing feathertop Rhodes grass on roadsides via frequent and timely slashing could be an option for managing this weed.

As part of the Area Wide Management project, options to control feathertop Rhodes grass on roadside verges have been tested. Working with the Millmerran Landcare group for the past two years, CSIRO researcher Brett Cocks has been assessing the impact of slashing.

Areas are slashed five times a year, just prior to seed-set and at the end of the growing season. Mr Cocks says that one roadside site has been monitored for 14 months and preliminary results suggest frequent timely slashing is working. In a bid to reduce the spread of weeds at paddock boundaries, the trial is also investigating how feathertop Rhodes grass competes with sorghum sown at different row spacings.

“Feathertop Rhodes grass has a highly mobile seed,” Mr Cocks says. “We are investigating whether we can manage the edge of the paddock separately from the rest of the paddock to control weed spread.

“We have replicated trials in a grower’s paddock that adjoins the road, with sorghum sown at three different row spacings – 25 centimetres, 50cm and 100cm.

“If growers are planting sorghum and have grass weed problems there are limited chemical control options available. We want to see if a feasible option for growers is to use agronomic practices, such as reduced row spacing around the edge of the paddock, to reduce the spread of weeds from paddock boundaries."

If we can control annual weeds and stop them from setting seed, councils, landholders and the wider community all reap the benefits.

It is early days, but the 25cm row spacing results are looking promising, he says. There are no weeds growing between the rows, compared with the 50cm and 100cm row spacings that are full of weeds. Given that feathertop Rhodes grass is very mobile in both irrigation and flood water, irrigation ditches are another area of concern for weed spread.

Replicated trials in areas adjacent to irrigation ditches are being investigated with sorghum planted at 25cm, 50cm and 100cm in the same paddock.

“We need to analyse the data fully, but preliminary results are the same with no weeds between the 25cm rows, while the 50cm and 100cm rows are full of feathertop Rhodes grass,” Mr Cocks says.

Paul McIntosh, WeedSmart agronomist (northern region), has been working on the project too and sees any options to manage seed movement as beneficial.

He has also recently flagged Queensland blue grass as an emerging weed issue.

The native semi-perennial has most likely spread following the past two years of heavy rainfall and increased overland flows. “It is being found in places it has not been before.”

More information: Paul McIntosh,;  Brett Cocks,

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