Australia - Problem weed feathertop Rhodes grass needs strict control

As the difficult-to-control weed feathertop Rhodes grass continues its spread south into the broader northern grains region, researchers are advocating a strict management regime.



Lawrie Price, research manager with the Grains Research and Development Corporation (GRDC)-funded Northern Grower Alliance (NGA) says the weed has made its presence felt in cropping systems over recent years and usual control methods aren’t always effective.

"GRDC-supported research shows glyphosate rarely gives satisfactory control of feathertop Rhodes grass,” Mr Price said.

"Registrations for alternative products are in the pipeline but a strict management package will be needed to be implemented to stop its spread.”

Over the last few years the weed has gone from being a common weed on roadsides but only a minor weed in cropping lands, to a serious problem weed in some paddocks as far south as Narrabri, NSW.

"The weed is present throughout the region and there are fears that it will explode in significance much the same way as fleabane has over the last 15 years,” Mr Price said.

"It has been a problem weed in central Queensland for some years.”

Mr Price said like fleabane and sowthistle, feathertop Rhodes grass is favoured by a zero till environment.

"It will germinate on the soil surface or from shallow depth after a small rainfall event,” he said.

"Cultivation which buries the seed to five centimetres or greater appears to prevent germination.”

Seed heads can be produced within four weeks under good growing conditions and plants produce many seeds.

Seeds are light and will stick on clothing and vehicles and can be easily spread to non-infested paddocks.

"Throughout the region there are areas where the weeds can be seen as clumps around roadside guide posts,” Mr Price said.

"We suspect tolerant biotypes have been selected for by injudicious spraying producing seed that can readily spread into cropping paddocks, together with an over reliance on glyphosate in our fallow management.”

NGA results show control levels of feathertop Rhodes grass drop rapidly as weeds become stressed so there is likely to be more success if weeds are sprayed immediately after rain.

Mr Price said GRDC-supported research carried out by the Queensland Department of Agriculture, Fisheries and Forestry (DAFF) has shown that seeds are short lived and will only last 12 months when buried at five cm.

"One or two seasons of stopping seed set can get the problem under control,” he said.

"Both residual and alternative knockdown products have also been shown to be effective in NGA and DAFF trials.

"A wide range of residual products have shown very good (but perhaps short lived) activity. Registrations are being actively progressed by a number of crop protection companies.”

He urges growers to be vigilant and even if feathertop Rhodes grass is not a problem at present they should control small clumps when they first see it. In many cases growers are opting to cultivate small patches to prevent seed set.

"Don’t wait until you have a blow-out to start management of this weed,” he said.