Key points

• ICAN has been coordinating feathertop Rhodes grass (FTR) demonstration sites at Dalby, Surat, Mungindi, Edgeroi and Moree
• The GRDC-supported work is allowing different management options to be explored
• A proactive plan, incorporating residuals, follow-up management and crop competition is effective

A proactive approach to feathertop Rhodes grass (FTR) management offers the best chance of dealing with this increasingly stubborn weed.

Working with Independent Consultants Australia Network (ICAN), leading northern New South Wales agronomists Sam Simons and Tim Poole from Poole Ag Consulting are managing one of the GRDC-supported FTR demonstration sites in the northern region.

Both agronomists say that the key to good control is a ‘take no prisoners’ approach.

This is because FTR is well-adapted to no-till farming systems fallows. Weeds can rapidly emerge after winter and quickly become too large for spraying. Glyphosate is usually ineffective, and the most-reliable post-emergent herbicides need to be targeted at very small weeds soon after emergence.

This all points to a proactive plan, says Mr Poole, who is managing the Moree sites with Mr Simons.

“Get on top of FTR early. Management plans need to be in place before the first spring rainfall – ideally by having an effective residual herbicide already applied or by being ready for an effective post-emergent double-knock, incorporating an effective residual in the second pass, within one to two weeks of emergence.”

The demonstration sites at Dalby, Surat, Mungindi, Edgeroi and Moree are allowing different options to be explored. This has further highlighted that residuals, follow-up management with optical sprayers and crop competition are good options, with cultivation instead causing trafficability challenges.

Northern NSW agronomist Sam Simons has been running a feathertop Rhodes grass (FTR) demonstration site allowing different management options to be explored. Photo: Supplied by Sam Simons

Cultivation

Although deep-rip strips at Moree had an initial impact on FTR germinations in the 2020-21 summer, late-season rain made trafficability challenging.

During fallow spraying, the lack of stubble also made it hard to manage dust when conditions began to dry out.

If cultivation is to be a useful strategy, Mr Simons says it needs to be aggressive.

“Even if you are not deep ripping, you want to make sure that you are cultivating to a depth of at least 10 to 15 centimetres to bury weed seeds deep enough to prevent their emergence. That can be difficult to achieve uniformly across the whole field.”

Residuals can be incorporated after cultivation, but this is far from ideal.

“After cultivation, we are often left with different-sized clods that lead to uneven distribution of the residual herbicide, resulting in weed escapes. So it’s not normally the preferred strategy.”

Crop competition

Crop competition can be beneficial in managing FTR, with species and variety selection crucial in achieving a heavy stubble load.

“Narrow row spacings and different header options like stripper fronts can help achieve high ground cover through the fallow, which can really suppress weed germinations,” Mr Simons says.

He says this approach will not necessarily achieve 100 per cent control but can be an integral part of any integrated weed management strategy. “Crop competition can have a big impact on suppressing weed germination.”

This can be more difficult to achieve in summer crops sown on wide rows, particularly sorghum.

“Where we’ve had a history of FTR, we won’t grow sorghum for two or three summers. Instead, it would be better to look at broadleaf summer crops where group 1 and other residual herbicides can be used.”

That said, narrower row spacing in sorghum is being investigated as a way of optimising crop competition, while some of the time-of-sowing (TOS) work is leading to earlier planting dates, which also enables the crop to get a ‘jump start’ on weeds.

“We can also split up the grass residual applications, starting in the fallow period, again at planting and also in-crop if required with chemicals such as Dual Gold (a group 15 chemical) to try and extend the residual control period.”

Residuals

Both agronomists agree on the importance of timely residual herbicide applications.

“If I had to pick just one FTR management strategy, I would choose to spray small, fresh FTR seedlings on time, following it with a double-knock, plus residuals,” Mr Simons says.

“Last year (2021), this worked exceptionally well when done on time and this year it will be no different.

“The Northern Grower Alliance (NGA) has done great work on which residuals work best and we all have access to those trial results.

“The key is to get the residuals down early, post-harvest. This will also give plenty of time to get the summer rainfall to break down the residuals before the next crop goes in.”

Both also suggest working out what the primary weed target is and planning accordingly.

“Herbicides targeted at broadleaf weeds can antagonise herbicides such as group 1s, so often we need to pick the main target and ensure the recommended spray homes in on that problem weed. We can’t always get it all in one spray,” Mr Simons says.

“If it is FTR and barnyard grass, make sure you nail them first with a knockdown, then a residual, and come back with a camera sprayer to address any escapes including broadleaf weeds. Most people have access to an optical sprayer now and can address broadleaf weeds later.”

Mr Poole agrees and says that where residuals start to break down and weed leakage has been seen, patch management strategies performed well.

“Those in the region who had camera sprayers were really staying on top of outbreaks. Other patch management strategies include quad runners and we’ve seen some drone technology too. Anyone who could stay in front of those light germinations really got dividends from it.”

Long-term benefits

Mr Poole says a proactive approach will also have longer-term benefits. “If we go hard at FTR for a number of years, we can get on top of it. We’ve really turned around some problem paddocks and we hope to do this in other areas.”

He suggests keeping an eye out for it. “You don’t wake up one morning and have a paddock full of FTR. You can see it coming in from fences and waterways. If we can get on top of these weeds early, then we’ll really stay in front of it.”

The flipside is falling behind. “Once you get behind the eight ball, it really is a struggle to control.”

More information: ICAN Rural - Feathertop Rhodes Grass.