Are you old enough to remember the days of Glean and Hoegrass?
No, Hoegrass is not a weed, for those of you born this century, it was a herbicide.
And they were great. They were the first of the selectives for killing ryegrass in wheat.
But when I say they were great, it’s a bit like saying a HQ Holden was great. Once again, for the millennials, a family sedan from the early 70’s.
We have nostalgic memories of old cars, but truth be known, they were pieces of crap compared to modern motoring.
They were heavy, sluggish, the brakes were terrible, you needed to do dead lifts in the gym to operate the clutch, they leaked water like a sieve, they rusted, and try and start one on a cold morning! You had to hold your tongue just right, two pumps on the accelerator, a bit of choke (millennials, google what a choke is), and if you missed it on the first go you were going to be at least 10 minutes late for work.
Glean and Hoegrass were HQ Holdens. Yes, they killed ryegrass, but they were expensive, they could be pretty hard on the crop, their job on the ryegrass was variable, and after four to six shots the ryegrass was resistant. And to make matters worse, there was cross resistance between the two.
We weren’t really into managing the seedbank back then. In fact, we were given 0.1m2 quadrats called Hoegrass squares, and we only sprayed when we counted more than 10 ryegrass in a Hoegrass square. This was designed to make sure growers got their money back from using the spray. As it turns out, it was also designed to speed up the rate of resistance development.
Our current suite of ryegrass herbicides are high performance sports cars.
Some growers could buy a Ferrari every second year with the money they are spending on these products!
But, there’s no denying, they work.
And, they are not developing resistance after four to six shots.
We have seen some cross resistance in a few nasty populations causing some of them to fall over, but for most growers, they’ll last a long time, particularly given that we are often mixing one or more pre-ems together.
Ultra-low seedbank farming
Now when I say these new pre-ems (and the odd post-em) are working, they are still 90% products. Maybe 93% in good conditions, but they’re not 98%.
90% control, year after year, will keep a seedbank pretty low, but can we go one better.
Can we use these products in combination with some other tools like crop competition and harvest weed seed control, and get to an ultra-low ryegrass seedbank?
The benefits
If we get to an ultra-low seed bank, what does this do for us?
- Resistance to the new pre-em herbicides is unlikely to happen. Resistance happens when a herbicide is sprayed over large numbers of weeds. If the numbers are low, and we keep mixing products, the risk is very low. Ryegrass finds it hard to develop resistance to these products as it is, and if applied in a mix, to a very low number of weeds, they could last decades. Then, some day in the future, you will find yourself with a suite of low cost, off label products to use over your non-existent seed bank.
- Some years you will get away without any pre-em herbicide at all. One argument would say that once numbers are very low, we shouldn’t risk it with no pre-em. But if we are clever, we will have the odd crop in the rotation with no need for a pre-em. Low cost, no herbicide damage.
- Camera sprayers might just be enough to clean up a few survivors. We don’t really have algorithms for ryegrass control in cereals yet, but that day will come.
- The big, new challenges with knockdown herbicides won’t be much of an issue if you have no ryegrass. There are other weeds with knockdown resistance that we will need to manage, but ryegrass is the big one.
You might almost be there
If you already have a low seedbank, you may only need to add one or two more tools to your system to get to the ultra-low status. Upping your crop competition and adding harvest weed seed control are two things that you can blanket apply to the whole farm to push ryegrass numbers even lower.
The higher your rainfall zone, the harder this will be to achieve, but the benefits will be greater.
This won’t appeal to everyone. The ultra-low seedbank approach will suit farmers who own their own land, who plan to farm for a long time into the future, and who are perfectionists.
This isn’t everyone, but then again, not everyone drives a Ferrari!
The Terminator Agronomist
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P.s. Ask the terminator a question by return email, and get a blunt answer next month.
P.p.s. Please note this advice is general in nature and not based on your specific circumstances.