Why doesn't weedkiller work on marestail?

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Barry
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Normal weedkiller tends not to kill marestail, apparently because marestail is coated in silicon, which prevents the weedkiller being absorbed through the plant's surface area.

However, if you spray marestail with a compost activator, such as ammonium sulfamate, you spray the outside of the plant, so I guess the liquid is absorbed via the plant's surface area.

So what is it about a compost activator that allows it to be absorbed and kill the plant that a normal weed killer lacks?

Do plants such as marestail draw in water or moisture through their leaves or roots? If they mainly do it through the roots, why has nobody invented a weed killer that works by being sprayed on the earth around the plant, rather than on the plant itself? That would seem logical to me.

If a compost activator is also better absorbed via the roots, again, why do we spray it on the leaves?

I've also met people who claim that they can kill marestail using Roundup, although it takes several applications. Can that be right? If so, how does that work?

Is there something they are not telling us, or am I missing something here?
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peter
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I think you're meant to damage mares tail prior to spraying, by crushing?
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Barry
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Perhaps with normal weedkiller, but a compost activator is simply absorbed by spraying on to a normal plant surface. Why?
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peter
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Could it be the molecule size?
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robo
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I use one sold by agrigem called pearl it's not cheap but works very well
Barry
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Robo,

I had a look at the Agrigem webpage and had a look at Pearl.

I can't work out the dilution rates, but AS is cheaper, at 200g per litre dilution.

Pearl also needs multiple applications according to the notes; AS kills everything and then becomes fertiliser!

http://mistralni.co.uk/collections/fron ... sulphamate
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I use 5mms per litre I usually add a little bit more but works on one application
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Johnboy
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Hi Barry,
What an interesting posting. All the threads have been positive and constructive.
My question is how did you come to use compost activator. If as you say it works well then this is quite a breakthrough.
Here I thankfully do not have marestail but when I was in Hertfordshire it was the bane of my life.
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Barry
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Hi Johnboy,

A friend of mine, who had done an OU science degree suggested it.

Compost activators are something of a nuclear option, though; they kill all plant matter that is sprayed and make it impossible to use the land for around three months.

The good news is that they are not toxic in any way and go on to improve the soil once decayed.

However, under existing legislation, we are NOT allowed to use compost activators in this fashion, since they are not licensed as such. Neverthless, I always manage to "spill" some ammonium sulphamate over marestail on my way to the compost bin :wink:

Yesterday, I was out "spilling" again, since some marestail that I didn't erradicate last year has begun to re-emerge. The adjacent area, which received a lot of "spillage" last year is totally clear.

The dilution rate is 200g per litre, but you are also advised to add a couple of drops of washing up liquid (which I forgot to do yesterday) to the mixture to make it stick to the plants. And it is this point that fascinates me: If sticking helps the plant absorb the AS, that means it is being taken in through the part of the plant sticking up above ground and not through the roots. If the plant will do that, why don't weedkillers get taken in in the same way?

The thing with marestail is that it is apparently coated in silicon, thereby making it difficult for weedkillers to be absorbed. Yet clearly liquids do get absorbed, or the AS wouldn't work.

I wonder if it might just be a question of adding washing up liquid to weedkiller, but that would be MUCH too simple a fix, wouldn't it? As I said above, I have met people that claim applying weedkiller three or more times does eventually kill marestail, but I have never done this myself, so I cannot comment.

I just wish I understood more about plant biology!!!
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Tony Hague
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Pearl is glufosinate ammonium. It is also the active in Kurtail, another product for mares tail. I had heard that it is better than glyphosate on mares tails, but it is not available to us hobby gardeners.

I don't know, but maybe it damages the cuticle of the leaf somewhat to gain better entry. Most glyphostate formulations will have wetting agents / adjuvants added, so washing up liquid or soap is unlikely to help. Not all are equal though, and the effectiveness of various brands of glyphosate is down to the adjuvants.

But I did have one thought I might test. We amateurs have two herbicides readily available, Glyphosate and Pelargonic acid. The former being systemic, the latter being contact only, but it's mechanism is damaging the cuticle and allowing desiccation to do the rest. perhaps a spray over with a Pelagonic acid herbicide followed rapidly by glyphosate might get more of it into the plant through the damaged cuticle ?
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I did buy kurtail it was a year ago it's freely on the web works a treat I just dribbled it on each one I did not spray everything with it
PLUMPUDDING
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It says that the ammonium sulphamate works by breaking down the woody part of plants so is good for tough weeds, tree roots, brambles,ivy etc. It works as a compost activator in the same way. Also it breaks down into non harmful substances so is reasonably safe.
Barry
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Do be careful using Kurtail.

If I understand correctly, it contains Agent Orange, which was used in the Vietnam war and is VERY nastly indeed.

Just reading the directions frightened me to death.
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One thing I've found when using these heavy duty herbicides is that they work better if you damage the vegetation first, either by clipping, crushing, or in the case of ivy or leathery leaves by tearing a few leaves, so the poison can penetrate more easily.

I agree with you Barry that just reading the instructions and warnings puts you off using them at all.

I read once that mares tail roots can go down to 30 feet, so you would need something pretty strong to kill it.
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Johnboy
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Hi PP,
When spraying Ivy with glyphosate I always add a small amount of rape seed oil and that seems to do the trick well enough.
You have to really use your equipment only for glyphosate as you cannot guarantee the cleanliness need for other uses.
JB.
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