Pigweed Control: Understanding Biology and Practical Solutions

0:09 Hi, I'm Dale Strickler with Green Cover Seed. How many of you have sprayed your soybean field over and over again and still have a field that looks like this photo? There's, as I drive around the country, there should be a lot of hands going up at this point.

0:30 Well, I wish that I had some sort of magic wand to give you that you could control those pigweeds, some sort of silver bullet. There isn't one. However, there are some actual real tools that you can use to control pigweeds like this AK-47 here. Now we're going to revisit this later, but I would like to start off with a quiz.

1:00 I want you to identify the plant in the picture. Anybody know what that plant is? There's a method to my madness here. That plant holds some importance for some things we're going to talk about coming up in the presentation.

1:14 Okay, first thing I'd like to talk about is some facts of pigweed biology. Why are pigweeds so hard to control? Well, the first thing is they're very prolific. A single pigweed plant can produce 600,000 seeds. That means if you have one pigweed plant per square foot go to seed, you could potentially have in one year two and a half billion seeds per acre. That's just a staggering number. Even if you controlled 99.9% of those seeds, you're still left with a million pigweeds per acre. That's just staggering.

2:03 Another thing is that pigweeds have an incredible root system. They have a really deep tap root, as you can see from this photo. But if we zoom in a little closer, you can see that we also have extremely fine fibrous roots, big long root hairs that are on those tap roots. So it's almost like a fibrous root and a tap root combined with the advantages of each. Our crop roots look nothing like that. We either have tap roots or fibrous roots, nothing quite like this.

2:43 Another reason, as you can see from this pollen count, pigweed pollen is a pretty severe allergen because it travels. That means that if we have a pigweed that has a gene for resistance to this herbicide or that herbicide, that pollen can travel for hundreds of miles in the air and pollinate a pigweed a long distance away. And guess what? That pigweed population will become resistant to that herbicide. So herbicide resistance in pigweed spreads extremely rapidly.

3:20 Another thing that makes pigweeds seem like a superweed is that they have a different carbon fixing mechanism, a different method of photosynthesis than what soybeans do or any of our other broadleaf crops like sunflowers. Their method of photosynthesis is closer related to corn or sorghum, which means they can grow three times as fast as soybeans in the heat of the summer. That's why, as you see in this picture here, this was an alfalfa orchard grass mix that was rotary mowed two weeks ago. Already the pigweed you can see is several feet.

3:59 Tall in two weeks of grow. Just like Superman has his Kryptonite, pigweeds have their weaknesses too. And if we understand these weaknesses we can exploit them and help control pigweeds.

4:14 The first weakness is seed size. Pigweeds have extremely small seed, and that small seed size means that each individual seedling has a very limited energy reserve.

4:29 So what does that mean? If it has very limited energy reserve, well the first thing is that it can't emerge from a depth. As you can see from this chart, pigweeds can't emerge if they're buried more than an inch deep. Now some people may think that that's a rationale for burying those seeds with tillage and then we won't have to worry about them. I'll show you later that's maybe not the best choice mainly because of what you see on this chart.

5:00 As you can see from the different chart, we have the depth of burial up in the upper right hand corner of this graph, and you can see that the deeper you bury the seeds the longer they live in the soil. You can see that seeds buried at 40 cm live a lot longer than ones buried at 1 cm in the soil, and just for reference, 40 cm is about 16 inches.

5:30 Another weakness that pigweeds have is that the seeds almost require sunlight in order to germinate. They don't germinate very well without light. Knowing that we can put that to our advantage.

5:44 Now this is a slide of a vertical tillage implement. Vertical tillage is getting to be very very popular these days. So how does this affect pigweed populations? Well a vertical tillage implement is actually the best pigweed planner ever designed. It works that shallow surface soil which is where pigweeds germinate, exposes them to light, takes them from the surface, covers them with a slight amount of soil or brings ones that are too deep and puts them up close to the surface where you have good germination conditions, creates good seed soil contact for pigweeds. When you use a vertical tillage machine you will get a flush of pigweed seed if there's any out in the field.

6:31 So you can either use this to your disadvantage or your advantage, as long as you know that this is going to create a nice stand of pigweeds. You can follow a vertical tillage pass with another shot of a burndown herbicide and kill the pigweeds while they're little. If you fail to do that, if you vertical till and plant and don't follow that up with some sort of weed control method, you're going to have a mess. And so it all depends on how you manage that if you choose to use a tool like this.

7:09 Another weakness of pigweeds is that they're very shade intolerant. They can't handle competition at all. As you can see from this chart, the blue bar is 7 and a half inch row spacing, the dark green bar is 15 inch row spacing, and then the light or avocado green bar is 30 inch row spacing. You can see the tighter the canopy becomes on your soybeans the less pigweed problems you have.

7:39 See the right hand set of bars there is where they put a residual herbicide in with their post emergence to extend that period of weed control out until the soybean are fully canopy. Because of that small weed seed size on the pigweeds, they don't have much energy. It also means they can't live very long in the soil. You've probably heard how velvetleaf or bindweed seed can last 50 years. Pigweed seeds aren't that long lived. About 90% of them lose viability in just one year, and they will continue to lose viability.

8:21 So theoretically, if you can eliminate pigweeds from going to seed for about four or five years, you're going to be about 99% or even better percent control of those seedlings without any expense for herbicides if you can prevent them from producing seed. How do you do that within a crop rotation? Is there a way that you can easily prevent pigweeds from going to seed for four or five years with a row crop just by crop rotation alone?

8:56 If you're thinking alfalfa, you're already ahead of me, because alfalfa has routine regular mowings that prevent pigweeds from going to seed. So you can see in this study, just the fact that you had alfalfa in the rotation decreased your amount of weed emergence dramatically. You can also see that about year five you start to get a little uptick in weed seed germination. That's because the alfalfa is starting to thin out. The key to making this work as a weed control strategy is to kill that alfalfa stand out while it's still a healthy stand. Most people keep alfalfa stands too long and they become nonproductive and they lose money for a year on that stand before they decide to kill it. Kill it while it's still making money and rotate out.

9:50 Final advantage is that pigweeds actually have a requirement for nitrate in the soil to germinate. If you can create a nitrate-free soil, you can prevent pigweed germination altogether. We'll show how you can do that later on.

10:09 So I've heard a lot of people talking. They said well, we've got 2,4-D tolerant soybeans coming out. We have dicamba tolerant soybeans coming out. Is that going to be the solution to all of our pigweed problems? We'll address that in a bit. The other thing I hear is well, we're just going to have to go back to tillage. Is going back to tillage a good strategy for controlling pigweeds? Maybe not, and I'll show you why I feel that way.

10:43 Look at this data. This shows a set of fields where within a crop rotation they prevented all weeds from going to seed. Pigweeds in particular were the problem weed in this set of situations. You see that if you prevent all weed seed production, there are fewer and fewer weeds each year that emerge in no-till situation versus tillage. And by the few last few years, you can see that the difference is pretty dramatic, about eight-fold difference in weed emergence.

11:21 In tillage versus no till, why is that? Well, the seeds just start to rot. They're preyed upon by slugs, they're preyed upon by insects, they're preyed upon by birds and they just, they're preyed upon by molds, rot, decay, bacteria, freezing and thawing, premature germination, all different kinds of things work at that soil surface to kill weed seedlings. When you bury them, you're not only planting them, you're promoting their longevity. So I think as a long-term weed control management strategy, tillage may not be our best answer.

11:57 Another thing that happens differently when you till is you change the timing of that pigweed emergence. As you can see from this graph, let's say we were planting at the 1st of June. Let's say we till and we plant on the same day, June 1st. Your crop's going to emerge shortly after that, but look at where your pigweeds are germinating. When you till, they're going to be coming up the exact same time as your crop and they're going to be highly competitive. Whereas in the no till, if you're planting June 1st, your crop's going to come up pretty shortly afterwards, but your pigweed emergence is going to be delayed. Remember, pigweeds are very sensitive to shade. If you can give your crop a head start with its big, large seeds, it has the advantage.

12:52 There's other drawbacks of tillage as well. There's soil erosion, there's water runoff, there's moisture loss through evaporation, and there's breakdown of organic matter. This study shows results of a study done by the University of Missouri and it shows how much organic matter was lost due to tillage and several tillage systems.

13:20 If you are backed into a corner where tillage is your only weed control option, say in wheat stubble or some situation where you don't feel you got a good chemical option or any other type of option and you want to do tillage, the least destructive tillage method you could probably use is to use one of these tools, which we call a V-blade or undercutter or Noble blade. What this does is it'll sever weed roots, but as you can see from the picture here, it leaves the mulch intact for soil conservation, moisture conservation. It doesn't flip new weed seeds up to the surface to germinate and it doesn't bring new weed seeds from the bottom of that tillage implement up to the soil surface where they can germinate. Doesn't bury them, doesn't bring them back up. So like I said, as a last resort, this is my, I guess I would say, my least hated method of tillage.

14:24 And some people have gotten really innovative with their weed control, non-chemical weed control methods. This is a called a mechanical weed puller. It's manufactured in Colby, Kansas and you can go to mechanical weed.com and watch a little YouTube video there. Rubber wheels are hydraulically driven, they spin, they grab.

14:49 The weeds and they pull them right out of the soil and the drawback of this is that if you got six foot weeds in your field they've already done their damage to your yield. This is revenge killing, but the benefit of this is those weeds are not going to seed. If these are herbicide escapes and you want to prevent spread of herbicide resistance and prevent adding to your weed seed bank in the soil, this might be a good tool.

15:18 Another one is a tool designed to mow in between 30 inch rows and you can see what it looks like after the mower is gone through it. It converts weeds into a nice little moisture conserving mulch so they change from a problem into a benefit.

15:37 Now the traditional method, especially in no-till controlling of weeds, has been herbicides, but we haven't been getting the results from herbicides like we have in the past. I mentioned that people are looking at dicamba tolerant soybeans or 2,4-D tolerant soybeans as the solution to our pigweed problems. How many of you have seen wheat stubble fields or fallow fields where they've sprayed Roundup Plus 2,4-D or Roundup Plus MCPA and not gotten a good control on pigweeds? I see it pretty often and it scares me that we are going to use 2,4-D and dicamba tolerant soybeans as a means to commit the same exact mistakes that we did with Roundup.

16:28 Roundup was a powerful weed control tool that we simply abused. We used it in our burndowns, we used it in crop, we used it in our fallow fields, we used it every chance we could because it was cheap and it worked, and then it stopped working because we selected for genes of weeds—weeds with genetics that had resistance to those herbicides. And now that's pretty much all the weeds we have.

17:01 Let's not go down the same road that we did with Roundup with 2,4-D and dicamba. If we overuse those chemistries we will have weed populations composed of weeds that are tolerant to those. Einstein said the definition of insanity is doing the same stupid things over and over again expecting different results. If we rely on 2,4-D and dicamba for all our weed control we will develop resistant populations. It's happened every other time we've done it, so don't do the same stupid thing we did with Roundup with 2,4-D and dicamba.

17:43 So let's look at some other alternatives. Not saying that's bad technology, but we're going to have to steward it better than we did Roundup Ready technology.

17:51 Now pre-emergence herbicides—one of the stronger benefits or stronger tools to prevent pigweed problems is to use pre-emergence herbicides. Whenever there's a pre-emergent herbicide or whenever there's a herbicide failure, people want to blame herbicide resistance. There are very few pre-emergence herbicides that we use in soybeans to which there is actually any documented actual resistance to the herbicide mode of action, but we do see a lot of failures and I have a list here of reasons for pre-emergence herbicide failure. Most of them center around either too much rain or too little rain.

18:35 I'll explain a little bit about which modes of action are subject to too little rain, which are subject to too much rain, and how that works. But very rarely is it actual herbicide resistance that's causing us a problem, with a few exceptions.

18:53 Burndown as a tillage replacement in no-till using burndown instead of tillage to prepare a weed-free seedbed. Gramoxone or paraquat is still a very effective burndown. It does not seem to have lost its effectiveness like glyphosate has. Now it's limited in its activity to smaller weeds, doesn't kill perennials, doesn't translocate to the roots, but it does provide very good burndown. It's very hazardous to handle. A lot of people don't like to mess with it, and I don't blame them, but it does work.

19:32 If you're using glyphosate as your broad-spectrum burndown, adding 2,4-D and Sharpen really helps pick up the activity. One caution is if they're using glyphosate ahead of corn, do not put your atrazine in with the glyphosate. Atrazine has a clay-based carrier that inactivates glyphosate. You'll get greatly reduced effectiveness if you're trying to do that.

19:59 Looking at soybean herbicides, pre-emergence herbicides, and how they work, why they fail, and why they succeed. I've got a list here of some attributes of the acetamides. Duel being the biggest one we use. These are highly water-soluble products. They only need about a quarter inch of rain to activate. That means they get in the soil very easily. They don't bind to the soil very readily, which means that if you get a big rain, these will leech through the soil and they won't work. A lot of people put these compounds on early this spring. In May, where I'm at, we had a very wet May. We had about 12 inches of rain in May, and 12 inches of rain will move these out of the weed seed germination zone. You'll lose effectiveness on it. But if you have gentle rains, they activate very easily. So these products work best when you have gentle rains. They don't work well either with no rain or heavy rains.

21:09 Another group of pre-emergent herbicides is the dinitroanilines. Of those, Prowl is the most commonly used one. These have very low water solubility, which means that they take a lot more moisture to activate than your acetamides. In fact, they used to recommend mechanical incorporation. But as no-till became more popular, these compounds started being phased out in favor of the Dual-type products that need less incorporation. The benefit of these is if you do have big rains after you apply them, they're going to stay in the soil and stay in the soil. The drawback is that if you have gentle rains, they don't activate very well. They need about 3/4 of an inch to get in the ground. Now your PPO inhibitors like flumioxazin with Valor, sulfentrazone like Authority, reflex, or premixes containing any of these are probably your best soybean.

22:21 Control pre-emergence herbicides on the market, they really do a good job. Another one that has a different mode of action is Senor. Senor is in the same chemical family as atrazine. If you have atrazine resistant pigweeds in your area, Senor is not going to be a benefit. If you don't, then Senor can be a good addition. Back in the days when Senor was all we had, we had to use very high rates to control some of the large seeded weeds like velvetleaf and cocklebur. If you're only using it to control pigweeds, you can keep the rate low enough that we don't get crop injury with this product.

23:05 This is just the results of a Michigan State study. Like I said, this is only one study. I've seen other studies where the effectiveness of these different products varied, but what I wanted to point out here is you can see that the PPO inhibitors, fosamine, and flumioxyen are the most effective single products out there compared to the dipyridinium or the acid amines. The other thing I wanted to point out is how much better control you get out of combination products. When you start combining modes of action, you're combining water solubilities. You're just covering your bases that much better.

23:57 Why do postemergence herbicides fail? Now, this is an area where herbicide resistance plays a much bigger role, but it's not the reason for every herbicide failure. Particularly with the PPO inhibitors, there are locations where there is documented resistance to PPO inhibitors among some weeds. But the biggest reason that we have failure of postemergence herbicides to work is that the weeds were simply too big at the time of application. I'll show you why it makes such a difference. There is a huge difference between a 6-inch weed and a 4-inch weed as far as how it reacts to herbicide.

24:43 Other things that can happen with postemergence herbicides, especially the PPO inhibitors, has to do with how we apply them. Some of your PPO inhibitors are things like Cobra Flex and Blazer and tank premixes containing them. These compounds are not translocated. They don't work like Roundup. They only kill the plant tissue they touch. They don't move down to the roots. Therefore, you have to get good coverage with these products. You should be applying at least 20 gallons an acre. You should be using surfactant, whatever adjuvant called for on the label. It's really important to use those adjuvants to get good coverage.

25:34 It's important to select the right nozzle. With most of our Roundup type applications, we were using low gallons of water and we're using nozzles designed to prevent drift. You don't want those types of nozzles with these products. You want nozzles designed to give good coverage, like flat fan nozzles. And you can see from this photo the damage that these products cause. They cause quite a bit of leaf burning. That's one of the reasons people were excited about Roundup Ready beans.

29:52 Of day is important you need to make sure that you're applying when there's sunlight to make these chemicals active. As you can see from this graph, midday applications much more efficacious than either early morning or late evening. Sunlight's necessary to make these chemicals work. Now a lot of times we have moved our spraying times away from the middle of the day because of wind. That is an important consideration, but if you're spraying in the dark, these compounds have much less activity.

30:30 20 years ago, 30 years ago, instead of spraying Roundup, Roundup, Roundup, we sprayed Pursuit, Pursuit, Pursuit, which was an ALS inhibitor. 30 years ago we created an entire pigweed population that was ALS resistance. Anything that is an ALS inhibitor probably has no value for controlling pigweeds at this point and hasn't for decades. Unfortunately, so anything that begins with an IMA in the chemical name, the active ingredient, or ends with euron is an ALS inhibiter and won't be effective on pigs.

31:11 And another method is cover crops. And generally when I speak in front of an audience and I talk about using cover crops as a weed control method, they kind of snicker and elbow each other like, yeah right, you know, if it doesn't have a skull and crossbones on the label it can't possibly kill pigs. Well, remember the picture of this plant I showed you earlier in the presentation? Very pretty ornamental plant. This is a Mexican bottle brush plant, scientific name is Callistemon, and from that plant was derived the herbicide Callisto, one of the most effective herbicides we've had in recent memory. You see the little pink logo next to the trade name on that jug? You ever wonder where that came from? That's the flower of the Callistemon plant.

32:09 There are compounds within some plant species that control other plant species. This is a plant's means of managing the competition around it. They can't run, they can't fight, they don't have claws or teeth or horns. They have to fight chemically because they can't move. And when plants produce compounds that have activity against other plants, that's called allelopathy. There are some cover crop species that have allelopathy in it, and basically plants are using chemical warfare just like chemical warfare was used in World War I.

32:56 Another means of action that cover crops can use against pigweeds: remember pigweeds had to have nitrate in order to germinate. If you can use a cover crop to suck up all the nitrate out of the soil and sequester it in the form of protein up in those leaves and stems, pigweeds can't compete. They have to have nitrate in order to germinate. If we combine a cover crop with precision placed fertilizer placed alongside the row where our crop can get it but our weeds can't, you can really reduce the growth rate of pigweeds and the germination.

33:41 One of the most effective cover crops for controlling pigweeds is cereal rye. Rye contains compounds called

33:53 Benzoxazines are benzoic acid derivatives as is the herbicide damba, so it's somewhat related to some commonly used herbicides out on the market. Cereal rye also has the ability to take up a very large amount of nitrogen. Usually soybeans follow corn in the crop rotation. Corn has a fairly wimpy root system compared to a lot of other plants. To do a good job of raising corn to get a good corn yield, you need to have a very high rate of nitrogen, and corn usually only actually uses about 75% of the nitrogen we apply to it, which means that you're going to have a lot of that nitrogen left over by the time you plant soybeans. That nitrogen not only feeds weed growth, it also delays the time soybeans begin fixing their own nitrogen. Free nitrogen is a good thing, so if you can use a cereal rye cover crop to sequester that leftover nitrogen from the corn crop, hold it in that residue, you'll eliminate the weed growth and those soybeans will start fixing free nitrogen for you at an earlier stage in their life—much as two or three weeks earlier. If you can do this, you're going to make your soybeans much, much more competitive against pigweeds.

35:30 Now some people are a little scared of rye because they have wheat in their crop rotation and rye can be a serious weed contaminant in a wheat crop. Triticale works very similarly to rye, not quite as strong, does have some better forage value if that's a priority for you than rye, and it's not as bad a contaminant in a wheat field as cereal rye is. Another cover crop with a very high nitrogen uptake potential is annual ryegrass. Ryegrass and rye are entirely different plants—don't confuse the two. You can see from this seed head that ryegrass is completely different than cereal rye, but just like cereal rye, it's a very effective pigweed control species. Look at this field—it was split half and half with and without annual ryegrass and then planted to soybeans. Look at the difference in weed growth between those two parts of the field. If you sequester that nitrogen, you reduce weed growth and get more free nitrogen from soybean nitrogen fixation. You also create a mulch there that can help control soil erosion and retain moisture.

36:58 This is from year 2012, not exactly the most favorable year in most areas. You can see the yellow soybeans were grown without a cover crop. Soybeans to the right were grown with a cover crop of annual ryegrass, and that part of the field did 10 bushel better. And if you want the best of both worlds, you can blend cover crops. This is a blend of triticale and annual rye dry grass, and you can see the multi-layered canopy. You can get a little more productivity. This is a very good grazing mix. The person who used this ended up chopping it for silage, made 10 tons per acre of silage harvested April 15th. Soybeans being planted no-till into a killed crop of rye, and you can see from this graph that even rye mulch that's not very thick can provide quite a little bit of suppression against pigweed.

38:03 Weed emergence at 1.5 kg per meter squared, which is at the far right, is 1,375 pound per acre, less than 3/4 of a ton of mulch per acre. That caused that amount of reduction in pigweed emergence. Remember, that's allelopathy, that's nitrogen tie up, and that's shade that's preventing those pigweeds from establishing. This is University of Georgia research, and you see the red bars is the weed control they got with cover crop alone without any herbicide.

38:42 You can see oats and rye both provided about 40% control, which isn't the greatest. But this is in a very challenging environment. Cover crops rot very rapidly in this environment, and there's a lot of rainfall and a lot of leeching, and so herbicides don't work very well here either. You can see that combining the cover crops and the herbicide treatments were much, much better than either one of them.

39:16 Now the sequestration of nitrogen is great in front of soybeans because soybeans fix their own nitrogen. Sequestering nitrogen may not be the greatest thing ahead of a corn crop. Here's where we planted corn perpendicular to a cover crop plot, and you can see as the corn plants hit the annual rye grass strip where the red arrow is, the corn plants basically did nothing. Corn has to have nitrate or has to have nitrogen in order to produce.

39:57 Soybeans can manufacture their own. So how can you use this cover crop concept to control pigweeds in corn or sorghum as opposed to soybeans? One way of doing that is to use legumes as your cover crop choice. This picture is of hairy vetch, one of the more productive winter annual legumes and also one of the more effective legume species at controlling weeds.

40:28 Now we think about legumes as producing nitrogen and grasses as tying them up. But legumes also tie up nitrogen. They're going to take all the nitrate out of the soil just like a grass will. And when that nitrate is gone, they'll nodulate and start producing nitrogen. If that nitrogen doesn't get put back out into the soil, it's up in the leaf material. So just like with the rye or rye grass or cover crop, that nitrate is not present in the soil to feed pigweeds. It's up in the leaf tissue.

41:03 Now it'll break down fairly quickly and start feeding your cash crop. But in the meantime, before that happens, it also keeps it away from your weeds. So you can grow a crop of hairy vetch, plant corn or sorghum into the killed stubble, and not have a lot of pigweed germination. Now you may have to supply some early season nitrogen to your plants with some starter fertilizer to make sure that your crop doesn't starve for nitrogen until that residue rots and decays.

41:39 One additional benefit of hairy vetch is that it contains a compound, an allelopathic compound called cyanamide. And cyanamide was actually used commercially as a herbicide many years ago, so it does work. Now the problem with the weed control of hairy vetch is

41:58 That it's very temporary, it only lasts a couple weeks, but if you can get your crop a head start on the pigweeds, a couple weeks can be worth a tremendous amount. Now remember that pigweed root that I showed you with the big taproot combined with a big long root hairs on it—the root hairs almost made it look like a bottle brush or a test tube cleaner. Our crop plants do not have that abundance of root hairs like the pigweeds do.

42:33 See, our crop plants co-evolved with an organism called mycorrhizal fungi, and you see this slide has the yellow crop root, and it's covered in all those little white filaments. Those white filaments are called mycorrhizal fungi—that's a symbiotic fungus that colonizes plant roots. The plant gives it a little bit of sugar, and it goes out and grabs water and nutrients and brings it back to the plant.

43:07 In exchange, a crop plant colonized with mycorrhizal fungi has about a thousand times the absorptive capacity as an uncolonized plant. Now the problem is, even though mycorrhizal fungi is native to all of North America—in fact most of the world except Antarctica—it's absent in our cropland. Mycorrhizal fungi co-evolved with perennial plants and have to have a live root as a host. So when we converted perennial ecosystems like the prairie from prairie into cropland dominated by annual plants whose root systems die each year, mycorrhizal fungi starved out.

43:55 But now mycorrhizal fungi are commercially available. You can inoculate with mycorrhizal fungi and restore that ultra-competitive root system to our crops. A crop root with mycorrhizal fungi will out-compete a pigweed root. Believe it or not, there's been some research done along those lines. Here is some research at the University of Florida that just shows how much more drought tolerant a mycorrhizal colonized plant is, showing the better water uptake.

44:29 This one's a little closer to home, and you can see the inoculated corn is much, much more tolerant of drought than the control. And there's some research out of North Dakota State that shows the effectiveness of mycorrhizal fungi on weed control. You can see that in this study, just making the plants more competitive against the pigweeds and the lambsquarters. Because pigweeds and lambsquarters are not benefited by mycorrhizal fungi—they don't host mycorrhizal fungi. Our crop plants do. You can reduce your pigweed biomass. In this study, reduced it 54%.

45:11 You can make a serious dent. Doesn't kill any pigweeds, but what it does is it slows their growth, it stunts them. That gives your plant the ability to grow above it. Remember, shade is pretty effective pigweed control. And remember how important it was to make those postemergence herbicides work, how important it was to keep the pigweeds under 4 inches in height. You can keep plants below 4 inches in height a lot longer by making your crop plant more competitive against it.

45:46 Okay, that's all I have for today. I hope you've gained some useful tips on managing your pigweeds. It's not all about newer and better herbicide.