For many years or decades even, our spraying of weeds, insects and even diseases with mostly synthetic chemistry has been largely successful. Certainly without doubt, we really have depended on our pesticide applications to provide us with successful and profitable cropping sequences.
You could add that overworked term in Sustainable in here as well. I would not like to consider how degraded and poor the productivity our broadacre farmland would be, if we just kept using the same old mechanical operations for weed and tilth control over the last 40 years.
I would like to speculate and reflect in this article about resistance… that is pesticide resistance.
For many centuries the human race has used a variety of means or techniques to grow crops and fibre to feed or clothe themselves and produce livestock fodder.
With the advent of a range of pesticides over the decades, we have learnt to use them very effectively and to great advantage in food and fibre production.
Particularly herbicides like Glyphosate, still the most important pesticide in the world, can really claim the benefits to mankind.
However, like many things, when we humans are on a good thing, we stick to it. Now that maybe true in other endeavours, yet when we deal with weeds, with insects and diseases, we definitely need to rotate our chemistry or modes of action.
So my photo this week is of a gnarly old weed of Fleabane in a chickpea crop and you may well ask: is that weed resistant or tolerant to the herbicide, was it too dry to have the residual herbicide activated, or has that weed and its root architecture been there since before planting over 4 months ago?
Now we do have our Fleabane weed species around this Northern Region resistant to various mode of actions or herbicides.
There is absolutely no doubt that when you continue to use the same mode of action in all our pesticides, over and over again and leave a few survivors, you will soon develop your own increasing level of resistance.
Sure, some of our popular herbicides, insecticides and fungicides are effective and relatively cheap, however continue to use this product singularly and you will bring big trouble into your cropping programme and probably your neighbours as well.
There is plenty of history in our part of the world with this resistance experience and yet many continue to foot fault on this vital part of our farming.
For example, Helicoverpa Armigera and the insecticides that no longer work on that insect.
My most recent big concerns are with our insecticides, of which we don’t have too many effective ones left and acceptance by our export customers ( with MRLs or Maximum Residue Levels concerns ) is even less than what we can apply here in Aussie land.
So not rotating modes of action, using lower than maximum label rates and achieving poor coverage are three major concerns that we should all be shouting from the rooftops about.
Weeds or plants out of place are sorta easy and if in doubt , just possibly you can plough them out.
If you have a plethora of difficult or resistant insects, then you are going to be using two bits of wood and watch your thumbs. Try doing that over 1000 acres?!
Disease spreading uncontrollably due to resistance is another level of pain, above the insect debacle.
So take it from an agronomist who has been around for 46 years now , that you need to mix and rotate modes of action, ensure excellent coverage and with weeds have no survivors setting seed post spraying for our future farming success.
Cutting rates and using what you have in the shed are poor examples of doing effective agronomy in our cropping endeavours.
Paul McIntosh has been involved in providing broadacre agronomic support since 1977. Since 2015, Paul has held combined roles with Pulse Australia and Weedsmart, as an industry development and extension agronomist. His regular weeds column is published in a number of places including New England Times Engage.
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