Here is an article I read. I cannot remember where, possibly in the Rural News, and I have condensed it.
New Zealand’s first confirmed case of a weed that’s developed resistance to glyphosate was announced by the Foundation of Arable Research [FAR] last week. Poor control of annual ryegrass in a vineyard was reported by a chemical company in 2011.
FAR CEO Nick Pyke says while the Marlborough find is, to date, an isolated case, it is a warning to users of glyphosate that they need to be aware of the danger of resistance developing and be careful how they use it.
RYEGRASS IS far from the only species of weed at risk of developing resistance to glyphosate, say Australian researchers, in the wake of New Zealand confirming its first case of resistance to the broadspectrum and widely used herbicide.
A new study released this week by the Australian Glyphosate Sustainability Working Group shows 23 of Australia’s weed species are at high risk of developing resistance.
The first glyphosate resistant ryegrass population was identified in Australia in 1996. Over the following decade 53 more cases were confirmed and earlier this year the tally was 347. There have also been over 100 situations involving five other weed species that have developed resistance to the herbicide.
The new study shows resistance could become a problem in any weed management situation. Of 200 weed species analysed to determine their innate likelihood to evolve and change in response to continued use of a range of herbicides, one in 10 were found to have a high risk of developing glyphosate resistance.
“Where a species is at high risk of developing glyphosate resistance, it is vital not to rely on a single herbicide,” says David Thornby, of Queensland Department of Agriculture, Fisheries and Forestry, one of several bodies involved in the Australian work.
“What this study shows is that we need to be thinking about how we use herbicides in every situation, both agricultural and non-agricultural weed control.”
My observation is that most people are rather half-hearted about their weed spraying. And it is this half-heartedness that puts us at risk of chemical resistance. I can remember my father’s disastrous experience on his kiwifruit orchard. He did not believe in wasting time mowing, so he hired a contractor to spray the whole orchard area with glyphosate. But each time he only did that when the weeds got too rank to walk through the orchard easily. This meant that the more resistant weeds quickly gained dominance and he was confronted with a chest high sea of willow herb.
So, I contend that you spray as if you are managing a car park, or you do not spray at all. Now that should get some responses to this blogletter?! Just to rub it in, here is an article I wrote a while back.
First Published in Feb 2005 BOP TCA newsletter
When I first bought my block, quite a long time ago, I had a theoretical understanding of how important weed control was. How it gave greater growth gains than fertilizer in many crops, etc. However, weed control has steadily risen up my priority scale over the years, so that now there would not be many things ahead of it. Good weed control gives those growth gains because it limits the competition for nutrients, it makes a crucial difference in water availability in dry spells, it affords easy access to the crop, and is a lot less work than bad weed control. It is the last aspect that has gained my attention.
One Tree Crops fielday at my place Bill Rae said that I had a scorched earth policy. I took that as a compliment. That is exactly what is needed under a crop, bearing in mind that a weed is a plant growing in the wrong place.
I have tried many different chemical regimes over the years, but the one that best met my requirements of minimum chemical use with minimum effort for maximum effect is the Queen Elizabeth Method. Queen Elizabeth I made the famous remark that she had a bath every year whether she needed it or not. Similarly, I go spraying every morning whether I need to or not. (This is a statement of intent, rather than actual fact.) Basically if you think an area needs spraying you are too late. Rather, you need to fill up your knapsack, say, “This is the area scheduled for spraying,” and go looking for the weeds to spray. There will not be any trouble finding plenty.
The aim is to be able to achieve the same control with hand weeding. Appleton’s Tree Nursery has achieved this over their huge nursery. They now hand weed, very economically. Eric Appleton made the observation that it takes 6 years after breaking a new piece of land in for the weeds to stop coming up. Which confirms the old saying of, “One year’s seed is seven year’s weeds.” The object is to break the seed cycle. Old Mr Davis, of Duncan and Davis, had the saying, “If you have no weeds, you have no weeds.”
Six years weed control before you can slacken the pace is a bit daunting. Actually it is not as bad as that. Even hard seeded weeds like gorse that can come up decades later, have greatly reduced germination even after a year. One of the worst weeds I have encountered is Amaranth. One species seeds after only about 10 days in the height of the summer, and the seeds last 40 years in the ground. Even this can be mastered with the Queen Elizabeth programme, if you really clobber it for a couple of months. I remember going to a demonstration of some new pre-emergent weedicide that was very effective on summer grass. The control was impressive, but if you looked closely, there were enough grass plants that survived to seed and ensure the chemical was needed again next year, but not enough to be a nuisance to the crop. I remember the rep. was perplexed by my not signing up for his product because I did not have ANY summer grass. The answer is that it is alright to use a pre-emergent spray as a oncer, provided that it is followed up with the Queen Elizabeth treatment to make sure residual chemicals are not ever needed again. Summer grass can be completely eradicated within two seasons.
A topic of much animated discussion is which chemical to use. Having tried most of them, I have gone for one that kills EVERYTHING and does not last in the environment. For your place that might be a different solution to mine, depending on the residing weed mix. If you were going to use glyphosate, the active ingredient in Roundup, then I would recommend you use Pulse as a penetrant. I have yet to find a weed that glyphosate plus Pulse does not kill. You may have to spray it more than once, but it will die in the end. When Queen Elizabeth does her next round, if there are any weeds still alive from the previous one, but now looking a bit sick, they get another dose. So willow herb, which has merely turned red, but is still laughing at you, will not think it so funny next time. Actually, this is one weed, if only occurring in small patches is best hand weeded selectively right from the start. Extensive areas of resistant weeds are best attacked with the right chemical, which actually kills them outright, but as part of a general area of weeds, I just use glyphosate plus Pulse everywhere.
People imagine spraying every morning is impossible because of the weather. Again the better your weed control, the easier it becomes, because you can hold the spray nozzle lower to the ground. I like to keep the nozzle within 2 centimetres of the weed, no more than 7 centimetres off the ground, and use as low a pressure as possible. (Experiment to find the right nozzle too.)
Any crop plant foliage can usually be held aside with one foot while spray is applied right up to the stem. If spraying around sensitive plants, and the weeds are more than a few centimetres high, trampling any tall weeds, or holding them down with a foot while spraying them is very effective. Rushes are much more effectively killed by squashing flat and spraying them when horizontal. It is not safe to apply all herbicides like this. For example some chemicals like Tordon, which re-vapourise, can damage your plants at close quarters. I now stop spraying if the wind is too strong to stand on one foot, or if it has actually started to rain.
I did kill a few plants in learning this technique. I remember discussing with a customer how we learnt our horticulture. I admitted accidentally killing a number of plants, and said, “You can’t help killing a few to extend the boundaries of what you can achieve.” He replied, “As a retired surgeon, I would have to agree.” I take no responsibility for how you might apply these techniques.
Having read this far, you are probably imagining that my place must look like a municipal car park, and that I must have a huge bill each year for glyphosate. I assure you neither are the case. The aim is to have minimum chemical use with minimum effort for maximum effect. So bare ground only happens where absolutely necessary. The stands of walnuts and chestnuts are pretty well weed-free to facilitate the nut harvest. Here a forest floor has developed. My anxieties about this technique were allayed in the July 2004, 100-year rainstorm. In spite of it being mid winter with no leaves on the trees, and the steepness of the ground, no noticeable erosion occurred.
I have found the Queen Elizabeth weed control method works well for me. I used it on the nursery, even amongst pots and rootrainer plants, and use it in my vegetable garden.
Now surely that will provoke some replies. Please do not take my remarks as advice, so tell us how you manage your weeds, or share experiences where spraying has not worked for you.
Your trigger-happy blogger.
nick nelson parker