Weed control expert, Barrie Hunt investigates the keys to keeping on top of problem grass weeds in the first of our new series of articles.
We know that even the most intractable black-grass, ryegrass and brome problems can be overcome. As can serious challenges from wild oats and even the couch that is again rearing its ugly head in some places. But we have to appreciate that the days of easy chemical solutions are rapidly disappearing for most and long gone for many. Not least with the spread of herbicide resistance and growing pressures on margins.
So, if we are to effectively keep on top of grass weeds these days we have to look well beyond the can, stacking cultural controls as much as chemistry. What’s more, we need to do so in ways that are carefully targeted, well-timed and highly tenacious.
Whatever the grass weeds we are dealing with, I believe there are five clear principles we must have at the forefront of our minds in securing the reliable, lasting and cost-effective control we need:
Better the devil you know
First, it’s essential we know exactly what problems we have and where. If we are to reliably combat grass weeds we need to understand which species we have, what really makes them tick and where they are most vulnerable.
At the same time, we need to know precisely where they are in our fields so we can apply well-targeted controls for the best results and value.
United we stand
Even though today’s chemistry can still be very effective, the rates and combinations of pre- and post-em herbicides required can be prohibitively expensive. Their success is also highly dependent on both the weather and seedbed conditions.
That’s why we need to take advantage of every cultural control opportunity we have – from rotations to drilling dates and cultivations to stubble treatment programmes – in a thoroughly integrated way if we are to achieve the sustainable control we want at an input cost we can afford.
Time is of the essence
Just as it is with herbicides, when we do things is every bit as important as what we do in our cultural controls.
Ploughing can be a big help in getting on top of black-grass, ryegrass and bromes, for instance. But ploughing two years in a row will bring buried seed back to the surface. Poor quality ploughing or ploughing under the wrong conditions can also do more harm than good. Equally counter-productive can be drilling too early even after effective ploughing.
A change is as good as a rest
Rather than shoe-horning the most appropriate cultural controls into our existing practice, we must be willing and able to do things differently too. Furthermore, we need to be flexible enough to change what we do to meet the needs of individual fields and changing conditions.
If we can’t get a good enough seedbed for drilling our wheat in the second half of October or early November, for example, we should switch to a spring crop. And where weed seed burdens are especially high we must be prepared to grow two or more spring crops in a row rather than assuming a single one will do the job.
There’s no quick fix
Finally, we have to appreciate the importance of persistence. If we don’t keep up the pressure with the most effective combination of controls, growing herbicide resistance and a declining chemical armoury mean we could rapidly find ourselves back at square one.
Its central importance in almost every cultural control strategy means we must also guard against the risk of glyphosate resistance development by employing it in the most effective and integrated ways possible.
In my experience, applying these five principles in practical programmes targeting black-grass, ryegrass, bromes, wild oats and couch – as I will be doing, in turn, in this series – is essential to the future viability of the cereal cropping at the heart of most UK arable systems.
We fail to do it at our peril.
As Roundup technical manager, Barrie Hunt co-ordinates the national on-line resource (www.monsanto-ag.co.uk/grassweed-action) providing the best information and guidance for growers keen to control grass weeds in the most sustainable way possible.