 Hi everyone, my name is Greta Graymig and I'm a weed scientist at NDSU in Fargo. Normally I would be speaking with you in person, but today we're going to have just a brief talk about Canada thistle and field bindweed nonchemical control. And so to get right into it, let's talk a little bit about these two weed species. The first thing that comes to mind is whenever I talk about these weeds, people are very interested because they have terrible problems with these weeds. And they think that I'm going to have a magical quick fix. And if that's what you're looking for, I'm sorry, I don't really have a quick fix. But what I'm going to talk about instead is an approach called integrated weed management where we can use several different tactics to try to get on top of these weeds and at least knock their populations down so that we can produce a crop or grow a healthy pasture on the land that's infested by them. And so here in these boxes I've got some specimens that I just dug up of both of these species and morphologically they are very different. This is field bindweed, it's a vining species. The Canada thistle produces a fairly tall maybe up to four feet tall chute and it's got these spiny glossy leaves. And this one is in flower, it's got these blooms which I'll talk about later. So they look different but they function very similarly as weeds and the reason for that is both of them have these extensive root systems. This is a Canada thistle root system. You can see the lateral roots and then this is a new plant growing from a bud. And the field bindweed will do the same thing. It's got these extensive roots that are many, many feet deep in the soil and it can also regenerate new plants from little tiny pieces of the root. For Canada thistle one little piece can maybe three quarters of an inch long can reproduce a new plant and these fragments can live for a hundred days in the soil. Some other problems with these they besides reproducing vegetatively from the roots they also reproduce via seed. And the Canada thistle plant will produce about a thousand to fifteen hundred seeds per plant and these plant these seeds most of them will germinate readily right away. But unfortunately some do go into the seed bank in the soil and they can live for about twenty years in the soil. And with the roots they can go about fifteen feet deep. This guy is even worse field bindweed it produces about five hundred seeds per plant and those seeds are very hard. They have a very impermeable seed coat and they can live for sixty years in the soil. So if you have a field bindweed problem chances are it's going to be very persistent both because of the seed longevity and the extensive roots which can go down twenty feet in the soil and a new shoot can emerge from a depth of about fourteen feet. And so it is very difficult to deplete the plants of the carbohydrate reserves in their roots and that's what we need to do to control them or manage them. There are many times when say you would like to use a biological control agent and there are biological control agents for these two species but unfortunately none of them really attack the root system. And so you can defoliate this plant and you think it's gone and the next year you've got a whole new stand that's because you didn't do anything to deplete the extensive carbon reserves in those root systems. So no matter what tactic you use that's the underlying key to successfully managing both of these species is you must get rid somehow of the carbohydrate reserves in the roots. So how do you do that? There are a number of different ways that you can deplete the carbohydrate reserves in the roots. The most common way and old school way of doing it is to use intensive tillage. So people would till very aggressively every two to three weeks and this over a field season will deplete those carbohydrate reserves to a great extent. It will not eradicate the weed but it will help. The problem is most people don't want to do intensive tillage every two or three weeks and destroy their soil and not be able to grow crop or pasture plants on that field that year. So what are some other ideas for things that you might do? One of the other tried and true methods that organic farmers use to manage these weeds is to grow a three year phase of alfalfa. Alfalfa is a perennial legume. It starts to emerge in the spring before the canada fissile and when you mow it, it also recovers faster than the fissile. And so you're using a combination of competition as well as mowing. Mowing alone can also be effective. And for both of these what you would like to do is mow at a point in time when the plant is sending carbohydrates down into the roots to store more of them. Early in the season the plant is mobilizing those reserves to grow the new shoots. Once these plants are in flower and this would be the perfect stage to mow or graze, not graze but mow canada fissile would be in this early bud stage because it's at this point that the plant's going to start to send all the photosynthate, the carbon down into the root system which is what you want to prevent. And the same would be the case for the field bindweed. And so growing some kind of crop that is hayed that you mow or hay two or three times a season will be very effective in reducing population density of these weeds and depleting those carbohydrate reserves. But some people are unable, they don't have hayen equipment, maybe they don't want to have a three year phase in alfalfa and so what else can you do? I mentioned crop competition. You can also use other crops that are competitive against these two weed species. And one of the fundamental principles that we teach in weed ecology is to grow a crop that's out of phase with the life cycle of your weed. And so for instance it's going to be much more effective to grow winter wheat than spring wheat. Winter wheat is much more competitive against canada fissile for instance because in the spring when canada fissile rosettes are emerging maybe in early May, that winter wheat canopy is already there whereas for spring wheat you've got nothing. So you have a competitive crop canopy all already in the spring that will be competing against those weeds. You can use narrower row spacing, you can try to plant earlier, anything you can do to increase the crop canopy. These plants are susceptible to shading, in particular the canada fissile cannot survive if it's not receiving at least 60 to 70% of full sunlight. So it is very susceptible to shading that needs sunlight and a crop canopy will really help knock that back. Another thing that you can possibly use is grazing and so there are animals, goats, sheep are probably the best, cattle will also graze canada fissile. They might find it a little less palatable than other things but if that's all there is they'll probably eat it. And the key to using grazing to deplete the carbon reserves and the roots for these species is to use mob grazing, very intensive grazing and less frequent grazing. So more intensive, less frequent grazing will help. And then another thing that you can do if you have a small enough space, say you're in a garden or you just have a small patch of one of these weed species, you can use mulching and the heavier the layers, the thicker the better. You could lay down a lot of organic material, top that off with some very tight landscape fabric or black plastic and just let it sit for a few years. That's going to get rid of it to a large extent or at least to the extent that you'll be able to function again in your garden. And if you have a very small patch, especially of canada fissile, you could try digging it out. Roots are fairly strong and they can be pulled out and dug out carefully if you just have a really small infestation and it hasn't been going on for very long. But that will not work for field bindweed because the roots are very brittle. And so hand digging is usually not very successful, unfortunately. And the idea again is to combine some tactics, use crop competition, use mowing, use tillage, control agents might help a little bit. They're not going to cure it by themselves, but some of the biological control agents will damage the tissue and allow other diseases to also impact the plant. So if you have enough of them present, they might also have some impact. And the key is just to be very persistent. You're not going to be able to focus on this one year and then forget about it. You're going to have to be constantly monitoring your infestations and using these control tactics to continually drive down that carbon storage in the roots. And you probably won't ever eradicate it, sorry to say, and unfortunately just leaving behind 1% of the roots is going to regenerate a new stand. And so persistence is the key and depleting those carbon root storage is key. And those are the main take-homes that I have to share with you today, and thanks a lot.