Feathertop Rhodes Grass (FTR)

Feathertop Rhodes (FTR) grass is a weed causing significant challenges for growers in northern cropping regions.  FTR is a summer growing grass weed that germinates and establishes quickly on small amounts of moisture.  It is difficult to control with conventional knockdown herbicides.  In areas with summer dominant rainfall, it can compete with summer crops and limit crop rotation choices. FTR grass is now commonly found growing in southern NSW, particularly along roadsides, railway lines and fence lines.  It has thrived on these areas due to; its tolerance of Glyphosate, the removal of competition through successive applications of Glyphosate, its ability to germinate after very small rainfall events, its ability to set large amounts of seed, plus the spread of seed by vehicles, animals and flowing water.

The proliferation of FTR on roadsides has led to significant concern over the potential spread onto broadacre farmland in southern NSW and the difficulty of controlling FTR in summer fallows, should this occur. Following are some characteristics that are relevant to the risk and control of FTR:

• Has a high natural tolerance to Glyphosate

• Can germinate quickly after rainfall and grow very rapidly, outcompeting other species

• A poor competitor with established plants

• Can have multiple germinations following small rainfall events

• A very short lifecycle, with germination to seeding in less than 6 weeks

• Can produce a very high number of seeds per plant

• Seeds are easily spread by vehicles, animals and flowing water

• FTR is a surface germinator and germination is significantly reduced if seeds are buried below 2cm

• Seed is short lived with seed viability no longer than 2 years

• FTR is very sensitive to frost

• Young plants are susceptible to application of some Group A herbicides followed by a double knock application of Paraquat

• FTR is likely to be sensitive to many of the commonly used pre-emergent herbicides used in southern NSW winter crops

• FTR becomes stressed easily during hot or dry conditions

Many of these characteristics make it very hard to control FTR grass with standard fallow weed management practices, predominantly post emergent herbicides.  However, there are several characteristics which will limit its ability to thrive in a winter cropping system, plus a number that could be exploited to control or prevent it’s spread.

Should FTR become established in a winter cropping system, there are several options available to producers to control it. Through the implementation of an Integrated Weed Management (IWM) plan, these options can lead to the effective long-term control of FTR grass.

The characteristics of FTR that growers can exploit for long-term control include:

• The short viability of seed (<12-24 months)

• The inability of seed to germinate from below 2cm

• Susceptibility to applications of Group A herbicides followed by a double knock with Paraquat

• Susceptibility to pre-emergent herbicides

• Inability to compete with competitive crops and pastures

Due to the short viability of FTR grass seed, any blowout can be controlled with only two years of complete seed-set control. However, proactive management should minimise the chances of blowouts occurring. Such management may include:

• Rotating herbicide groups on fence lines and not relying on Glyphosate to limit the incursion of FTR grass into cropping paddocks. Where FTR has become established, a Group A herbicide may be required.

• Utilising a double knock strategy to improve weed control and slow the development of herbicide resistance.

• The use of residual herbicides. These may be applied directly to a fence line or problem area. Alternatively, the later application of products such as Atrazine and Simazine in TT canola, may provide some residual control in fallow situations.

• Strategic tillage can be an effective tactic to control mature weeds, while also burying a significant proportion of seed on the soil surface. Tillage could be done in conjunction with incorporation of lime or residual herbicides, which would also reduce nutrient stratification and compaction issues. The use of full disturbance seeders will also significantly reduce the seed bank due to seed burial.

• Managing pastures so that they remain competitive will prevent FTR establishing during the pasture phase. Should pastures start to thin out and become infested with FTR, the problem should be addressed quickly before significant seed set occurs.

• Attention to detail. Where the above methods have been employed, it may be necessary to manually remove survivors to prevent them from setting seed.

FTR grass is now widespread throughout southern NSW and will ultimately begin to invade cropping areas during summer fallows.  Relying solely on current weed control tactics will lead to FTR becoming widespread throughout cropping paddocks, significantly increasing weed control costs while reducing moisture availability for subsequent winter crops. Despite the challenges of controlling FTR grass, it can be effectively achieved with the diligent and proactive adoption of an IWM plan.