Control Thistle in Pasture

[mhittinger]

There will be a demonstration/workshop near Athabasca on Thursday Aug. 31. This event will hilight training livestock to eat weeds like Canada Thistle and Tansy, two very tough weeds to kill. Molasses is a great tool to use for this, and a feed analysis on Tansy reveals 21.5% protein and 65% TDN. The thing about Tansy causing abortions is also a myth. If you are interested in attending, please call Mike or Vicky at (780) 939-8374. Leave a message.

[mjohn]

Just to clarify. In Alberta we usually refer to Tanacetum vulgare as 'Tansy'. Other provinces may be refering to Sencio jacobaea or 'Tansy Ragwort'. They look a little similar, but Sencio flowers have petals while the Tanacetum flowers are just little yellow 'buttons.

The reason I make the distinction is that 'Tansy Ragwort' is fairly toxic and livestock poisonings are common. The poisonous compounds in the Tansy Ragwort are called alkaloids. This type of toxin usually causes irreversible liver damage. It is also possible that these types of alkaloids are fairly carcinogenic.

Common Tansy (Tanacetum vulgare) also contains several phytochemicals that could cause problems. The abortion concern isn't really a myth, but the amount consumed would have to be substantially high to cause problems. The compounds of concern are terpenes and terpenoids such as Thujone. Thujone is a fairly well known drug and a liquer made from Absinthe is known to contain it. Rumor has it that a famous painter was soused on it when he cut off his ear, but then it was also rumored that he sometimes ate his paint. At any rate, these compounds can have side effects and are considered teratogenic in that they could cause birth defects or abortions.

In the case of Tansy, the amount consumed must be fairly high, or we would see more problems with it than we do. One real interesting aside is that these same compounds may also have some benefits. Some research on wormwood (absinthe) containing thujone, has indicated that it could have limmited insect repellent and anthelmintic ('de-wormer')activity. It is kind of intriguing that they are rediscovering the effects of some of the old folk medicines.

Controlling tansy and thistle without having to resort to herbicide is a good tool for us to have. Training cattle to eat weeds is a great idea! My point would be that the operative word is 'training' not 'forcing'. I have no idea how much tansy a cow would have to eat before problems would occur, but it is likely a lot. If she has been trained to eat it and balances her consumption with decent grass then there should be no worries.

[cakadu]

Weed inspector told me many years ago that if you mow the thistles and it rains hard, they will essentially drown, or rot. This year we didn't have to mow - that bad hailstorm did the job for us. Then the additional inch of rain we got the day after that helped them on their way to drowning.

The sheep will take the buds off and prevent them going to seed. They are the best weed control that we have.

The question that I have about chemical treatment relates to whether you are treating the problem, or a symptom? If you have to go towards stronger and stronger applications, or moving to different chemicals to do the job, then are you really treating the problem? If you don't change grazing practices etc., then won't you continually be treating the symptoms?

Nature abhors a vaccuum and the weeds grow because they can. We are slowly eradicating our problem, but again, it came because we rented the pasture out to someone who swore he wasn't going to overgraze and guess what happened? We are left to deal with the problem.

It seems to me that if you continually graze the pasture too short and attempt to eradicate the weeds without making other changes, the only thing you're doing is making the chemical companies richer.

Call me what you will, but I certainly don't want to get onto the chemical merry-go-round.

[rook]

A strong shot of Ally has worked for us. Cheap, safe, and a few years residual.

[smcgrath76]

I would certainly concur with your thoughts on symptom vs. problem cakadu. Back when we had sheep (120 ewes) thistles were gourmet forage.

For cows, thistles make a lovely place to feed minerals. The best overall treatment we have found for thistles is to let grass grow. A one time shot of Grazon or Roundup or whatever may work, but only so long as you change the system surrounding the problem in conjunction. I know people think we are nuts to waste grass when 50% or more is left behind, but we don't feed cows in summer or most of the winter and we actually have higher carrying capacities because of this practice. The old timers are right when they say "it takes grass to make grass". I have some reasearch and some math here that supports the theory. Letting grass grow is a great form of cost reduction, weed control, and drought insurance.

Thistles are actually pretty good forage and another good way to make them palatable is to silage them.

[coppertop]

The donkeys loves the young thistles. Only problem with that is donkeys are tough on wooden fences so the thistles might be the lesser of two evils !

[exnaboe]

An interesting discussion. I'm glad that some folk manage to control their thistle population by "natural" methods. We try to be effective grazers, practising rotational grazing and trying to balance consumption and rest periods. However there are places where the thistles have taken hold and mowing is not possible, unless with a scythe, and lacking sheep, goats or donkeys to help us, chemical control appears to be the only option. I recall a Forage Association tour where an Ag student had an experiment in essentially forcing cows to eat the thistles. They will when hungry enough, but this looks rather self-defeating to me. I have a neighbour who has proved this with a Longhorn herd. With sufficient overgrazing great patches of thistles do indeed disappear to my - downwind - relief.

[grassfarmer]

exnaboe, Research done in the States - I forget the persons name but I think it was at Univ. of Utah showed that you could teach cattle to eat thistles but you should/could not teach them by starving them or forcing them to eat them because they had nothing else available. Teaching cattle to broaden their diet to include thistles would seem a very worthwhile exercise. I haven't needed to because a proportion of my herd already graze thistles and they seem to be teaching the rest. There is a history of browse grazing bred into some of my cattle.

Cakadu, we never had much success with thistles and sheep (maybe different breeds?)- indeed I find we have less problems under a cattle only system than under a cattle/sheep system as I believe thistles seeds can pass through a sheep viable which they can't with a cow? Even if your sheep do eat the buds you will still get spreading by roots as that is where about 60% of the thistles reproduction comes from.
I was brought up with the cutting stems/rotting theory and it seems to work if you get enough rain to drown them out. Many people find it doesn't work as well nowadays as it did years ago and I think that the increasing use of disc or flail cutters smashes the cut stem tops up thus not allowing the water to enter the stem.

[cakadu]

The best thistle control we ever had was with the goats - they would eat them quite short. As coppertop has point out however, the goats were far harder on fences and the lesser of the two evils was to see the goats go.

While not as quite efficient, the sheep do tend to eat the thistles. They also eat things like stinging nettle - at a certain stage anyway - and they absolutely love pigweed. Don't ask me why, but they will literally fight each other to get at it.

I do believe that your assessment about not being able to "starve" something to eat thistles is correct. How many pastures do you drive by where there isn't a blade of grass to be seen, yet the thistles are going to seed?

We have also spent many hours cutting them down with a sythe. I don't know if we would ever be to the point that we would use chemical control. We'll see how they fare after this last hail storm. I doubt we'll see much regrowth this year, but I suppose that depends on conditions over the next few weeks.

[grassfarmer]

Yeah, I spent many hours in my youth cutting thistles with a scythe - a soul destroying job except for on very small areas!
I could take some great pictures just now of our roadside ditches which are full of waist high thistles, yet they more or less stop at the fence line. This tells me we are at least close to managing the threat from thistle invasion with our existing management.
So much for the theory that if we didn't control "our" weeds the county weed inspector would be ordering me to use chemicals to destroy them!

[cakadu]

I find being out there cutting those thistles is good stress relief, not to mention it is one of those tasks that requires next to no thought, which is good sometimes. Either that or I find that I spend a lot of time thinking.

Either way, I end up feeling as though I have accomplished something - at least for the moment.

[coppertop]

Interesting to note that the fellow across the road pastured a large number of horses on one quarter of land for years, including 2002 during the drought. The pasture was eaten to the dirt, then he sold the horses and pastured cows on the same land. There is no sign of thistles anywhere except around the vacant buildings. In this area the county ditches are relatively free of thistles but I can't say the same for the primary highway ditches !!!