The competition method
Controlling weeds in a time of increased herbicide resistance
ONCE again I write about the issues of weed control and what options we have in this era of increasing herbicide resistance on much of our weed spectrum.
For the last 70–80 years we have had effective herbicides like 24-D and, more recently, glyphosate to control our weeds in pastures, crops and fallows. These easy days of weed control are drawing to a close, aren’t they?
Now we have to think a lot more when we consider weed control. Cultivating, spraying a four-way mix, double knocking or burning the weeds and weed seed may flit through your head as options.
I have been giving this plenty of thought, as though I was a land manager with various weeds in sensitive or difficult situations.
I believe I would be trialling the competition method. In other words, I would be using a desirable or maybe a less troublesome plant to be an active and strong competitor against my weed spectrum.
For example, let’s look at feather top rhodes. This is a real challenge, isn’t it?
What could I encourage or grow that would out-compete a vigorous plant like FTR? Remember I am considering trailing different plant species against FTR, which is more or less an annual plant.
So from this book of experience of mine, I recall an older grazier gentleman in the early 1980s, who planted buffel grass seed among a lot of galvanised burr from the Chenopodium family. He then fenced it off and let nature take its course and advised a much younger me to keep an eye on the results and fully assess in 12 months’ time.
It was only a few acres, however he wanted to take a solid stand against galvanised burr encroaching from the neighbour’s place.
The results were startling to say the least. After 12 months in which he did receive some useful autumn/winter/spring rain, the gal burr was nearly non-existent and the buffel was very strong and vigorous in its growth.
Galvanised burr may only live for a few years but it does have a handy ability for its seed bank to remain viable for some years. The trick of beating this weedy plant is understanding that its seedlings are poor competitors and it is a slow-growing plant.
So now what could we match up as a competitor to FTR? You probably realise that nine times out of 10 a perennial plant is going to outperform and outgrow an annual plant given a reasonable start.
How about we consider the oldest fodder crop plant in the world – lucerne. Not the only option to consider, however with lucerne at least it is a useful plant and grass control can be a multi-pronged attack – constant mowing, selective grass herbicides, residual herbicides with various modes of action and, of course, the sheer longevity and toughness of this favourite legume plant.
When you plant lucerne for a commercial irrigated hay stand we are talking about
❝These easy days of weed control are drawing to a close, aren’t they? — Paul McIntosh
50–70 plants per square metre. Fierce competition to other plants around it, wouldn’t you say.
I know the definition of a weed is a plant out of place, however if I am going to have a plant out of place, I will take lucerne or some other considered option any time over a weed like feather top rhodes.
Where could I use this technique? That answer is in your court. Lucerne is only one option, however I have observed it many a time to outperform tough perennial weeds such as nutgrass and annuals such as urochloa and barnyard grass.
What I am suggesting is the principle of the competition issue, in those areas like waterways and fence lines etc, that harbour lots of weed numbers and are great weed nurseries for infesting our productive country.
Sure, it may be be difficult to establish them but we may only be planting a competitive plant in those tricky smallpercentage areas once. That has to be better than letting a single big flourishing FTR plant drop more than 100,000 seeds onto or around your productive paddocks.
Give your own situation some thought and plan your weed control in advance using some cultural methods and keep me informed as to your ideas and results.