Control of fleabane in stubble retained farming systems

Case study: Paul Adam, Tottenham, NSW – The control of fleabane in a stubble retained farming system.

Property: 1620 ha CTF with retained stubble on one property and mixed farming on 1000 ha of leased country south of Tottenham.

Enterprises: Wheat, canola, pulses and sheep.

Soil type and pH: red clay loam with a pH of 5.5 to 6.

Overview:

Paul farms a controlled traffic farming system on his home property with full stubble retention, while maintaining a more traditional mixed farming enterprise on leased country nearby.

He grows mainly wheat and canola with some pulses but has pulled back slightly from pulses in the past 12 months due mainly to difficulty with efficient weed control.

Issues and observations of fleabane control:

Fleabane first became an issue for Paul in 2010. There had always been small populations on the property but grazing by sheep had kept it somewhat suppressed. Since removing sheep from the retained stubble area that control no longer existed, leading to a surge in weed population.

In 2010/11 control consisted of a double knock spray. He admits they were a bit late getting onto it that year due to a wet harvest continuing into January. As a result the weed was a problem in the subsequent crop and had a negative effect on crop yield.

His program now consists of maintaining a double knock if for some reason early control was delayed but the focus now is on targeting the weeds as early as possible, in crop.

As a result Paul has moved away from later 2,4 D applications, instead using LVE MCPA earlier in the season with, say, Lontrel for some residual control .

Control of fleabane in pulse crops has become a real issue and as a result Paul is starting to move away from growing pulses. For example in a crop of faba beans Paul has had to do four sprays, mainly for fleabane (and sow thistle), where by comparison a canola stubble has had just one spray.

Bringing sheep in to graze on the full stubble retained system is a potential option for Paul but not one he’s keen to pursue as he is quite happy with the two systems he now has in place.

Tillage is also used on the mixed farming country but Paul tries to avoid this using on the retained stubble system unless completely necessary, such as renovating tramlines that were damaged by a wet harvest and control of difficult weeds such as windmill grass. But the benefits must outweigh the negatives.

On the mixed farming property growing cover crops is part of the farming system and vetch is one crop Paul has used in the past. He is considering doing some brown manuring with vetch not only for soil health and nitrogen fixation but also as a further tool for fleabane and other weed control.

However grazing by sheep still play a large role on that property in the control of fleabane.

One issue Paul is concerned about into the future is the current dependence on just a handful of chemical groups in the early control of fleabane. Future research into new chemicals needs to be done in the event of resistance developing.

Key issues in fleabane management in a stubble retained farming system:

In Paul’s experience focusing on early, in crop control is paramount to successful control. Double knock is a great strategy if you’ve missed the boat but should be looked upon as a secondary strategy. Once it’s at the stage of stem elongation it’s very difficult (and expensive) to get good results.

One interesting aspect of using a double knock Paul has found is that the timing of the second spray with five to seven days after the first application is critical. But for some reason he’s not fully understanding of, in the second application there seems to be a short window of early evening to around 10 pm where spray results are most effective. Outside of this short window results are more variable and less effective.

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