28 May 2024. Paul McIntosh, Pulse Australia and WeedSmart.
Once again, I was starkly reminded of the increasing specific weed issue of Annual Ryegrass in several paddocks and roadsides of southern Queensland.
Southern and western parts of Australia certainly have felt the full brunt of this very pesky plant of place, that we call a weed. Sure, Annual Ryegrass or ARG has fed a lot of livestock over the decades in Australia. However, now we want to crop these former feed paddocks, this plant has worked out that it can develop resistance very easily to our popular knockdown herbicides like Glyphosate and the Group 1 mode of actions in Fops and Dims.
Mainly a winter or cooler months growing plant, I have witnessed it growing on roadsides, around guideposts and other signage furniture in southern Queensland parts in October and November. Add in the actual folds or levels of herbicide resistance, these now northern migratory plants from down south have developed and Houston we have a problem.
They arrived here by grain and hay being “imported” from southern areas in our drought times. Our flat country with wide table drains is perfect for spreading the seed around our region with overland water flow plus by our own machinery movements.
What to do about these shiny leaved grass weed incursions?
Well, the first rule is to not let them go to seed by any means. Chip hoes, cultivators, constant slashing, or mowing will all assist stopping or reducing seed set of this weed.
Do not assume it is easy to kill with either robust rates of glyphosate or Group 1 (previously A) products. Crop competition and starting off planting with clean fallows is a key action my fellow WeedSmart agronomy extension colleagues tell me.
In our winter cereals it is trickier and many have now moved to using residual herbicides like Sakura (active ingredient pyroxasulfone) and others, to get control over this highly herbicide-resistant plant.
Of course, if it was easy, then ARG would be easily fixed...nope. Many of our successful residual herbicides need incorporation to provide good weed control and maximise crop safety.
Doesn’t quite suit our minimum till or conservation farming systems does it?
A term called IBS or “Incorporated By Sowing” appears on these more Southern products labels, that are fully registered in Australia and are somewhat volatile.
They mostly act on the roots of the small developing ARG plant, after a rainfall event fully incorporates the active ingredient of these residual type grass herbicides into the soil profile more.
So the plan is to apply these types of residual herbicides onto your flat pre-plant soil bed, then sow into the soil normally, pushing to either side of the seed trench, the treated soil leaving a clear gap where the cereal seed is placed and hey presto. It all works…or does it?
What about the cereal planting line where there is no herbicide and as there will be, weeds like ARG germinate and grow.
That is where other residual herbicides can be applied post plant, that do not require incorporation for weed control.
This highly herbicide resistant plant called Annual Ryegrass is a weed in our farming systems not to be trifled with folks. It costs millions of dollars per year for farmers to control this plant, so I suggest keep a good eye open for it and take some positive action if you discover this weed.