 I want to welcome you to this May 15th webinar. My name is Steve Brown, Extension Cotton Agronomist with Auburn University. We're going to explore how we think about plant growth regulator use in cotton. Specifically, looking at a broad range of topics from background of its history, it's how it affects the plants, some of the products that are used, and various use patterns that have evolved over the past 40 years. Then finish with a few questions for thought. It really is a thought process because there's not an automatic exact recipe as we think about PGRs in cotton. Practically speaking, when we talk about plant growth regulators in cotton, we're really talking about a singular product, and that is mepiquat chloride, and the products that are very similar or derived from it. Initially was introduced in the late 1970s by BASF under the trade name of PICS. Even today, when people talk about PGRs in cotton, whether it's that brand or a generic, they still talk about PICS in cotton, so that brand name has stuck. Initially, the product use approach, the label direction were very specific. You would use a pint at early bloom or first bloom, and then follow with a half a pint. But very quickly, academia, as well as farmers began exploring, maybe there's some other ways we could think about using this particular product. Now, when PICS was introduced in the marketplace in the late 1970s, US patent life was 17 years. Now, in 1995, that was changed to 20 years. But practically what that meant was, in the early to mid 1990s, we began seeing the introduction of enhanced mepiquat products, BASF trying to protect its position in the marketplace. We've also saw about that same time, the introduction of generic products. Now, it is truly a generic market today, and that's reflected in pricing. Initially in the late 70s, PICS products were probably costing the $40 per gallon range. Some of the enhanced products at some point in their lifecycle were $90 per gallon. Today, you can buy most mepiquat products in our part of the country for less than $10 a gallon. It's a product that's been in the marketplace for decades now, but it really provided a very, very valuable tool for cotton producers to manage the crop. Yes, you could do so with irrigation perhaps or fertility, but really the mepiquat provided a tool to control plant height, to limit vegetative growth somewhat, and again, a great management tool that really has become an integral part of modern cotton production. Now, how does it work? What is the mode of action? Well, if we step back, plant growth is certainly affected by environmental conditions, weather patterns, temperature, as well as soil nutrients, but at the basic and biological biochemical level, it's affected by plant hormones or plant growth regulators. They really work together in a very sophisticated complex system to manage how different processes proceed in the plant. I've listed several plant growth regulators that are commonly recognized, but for our purposes in this discussion, we should think about gibberellic acid. It promotes cell elongation, and then specifically mepiquat chloride inhibits the synthesis of gibberellic acid. So, again, very practically, then mepiquat reduces cell or tissue elongation. So that's its basic mode of action. Then what are the effects that we see in the plant? Again, keeping in mind that mepiquat reduces cell elongation by inhibiting gibberellic acid synthesis, it really affects the overall plant canopy by reducing plant leaf area and stem tissue length or internode length. The labels list a lot of these effects that I put here, but consistently it does these things, but not necessarily these things. Yes, some of the, some data suggests we see better early season fruit retention, and then consistently we do see a darker leaf color that seems to be attractive to us as we think about cotton. And then some of the labels also suggest that many of these effects here would have a positive impact on yield. However, I would say if we had 5,000 studies on mepiquat in cotton, I would say probably only a fourth of those might show an increase in yield. The others would not, but consistently, it does represent a tool, provide a tool for farmers to manage plant canopy and development, particularly in relation to size. What about the products? The original product was picks, branded picks, mepiquat chloride at 4.2% or 0.35 pounds of active ingredient per gallon. We've seen other products that are quite similar to the original, that is mepiquat chloride plus a bacterium or a plant hormone, or even a little bit different salt. And we've also seen it even as a water soluble granule, but most of the products that we talk about, and certainly these that I'm pointing to, we use them almost identically to what we do of the original product, the 4.2% product. Now, one product that does differentiate itself, it is different, it is called Stance, that's the trade name. It was introduced in the early 2000. It contains mepiquat chloride at twice the rate of the other formulation, but it also includes a growth hormone called CycleAnalid. And we do use Stance differently, and at different rates than we use the other mepiquat products. CycleAnalid by point of reference is the same plant hormone added with ethophon to make the premium harvest aid finish. So use patterns, again, we lump most of the products together in the original 4.2% formulation. And those uses are at early bloom, or thereabouts, and then applications thereafter. As I mentioned earlier, the academic community and became up with the idea, hey, this is a plant growth regulator, so maybe we would benefit from a spoon feeding approach and make a low dose applications. Just to point out on the label, the maximum use, one time use rate is 24 ounces or a pint and a half per acre, with the total uses of 48 ounces per acre per season. Stance, again, a little bit different product is used more typically at rates of two to three ounces per acre, but it does have a maximum use per season of 22 ounces. All the mepiquat products have a 30-day pre-harvest interval. Applications should be made at least 30 days prior to harvest. Now, again, looking at label use patterns, this is a label that's been in place for 40 years. The original label specifically dealt with applications associated with bloom. And we see those rates from a half to one pint with follow-up applications thereafter. The low rate multiples, again, is the approach of sort of spoon feeding initiated at match head square, early square stage at a low rate of two to four ounces with up to even four applications that range up to even 12 ounces per acre. But this is, again, an approach to give a little bit of long. And then in the last 15, 20 years or so, we've seen a late season application instituted, and that is a cutout application made in the latter weeks of bloom, maybe the sixth or even seventh week of bloom, try to finish the crop out. But these are the label use patterns. Now, this is a product that's been in the marketplace for 40 years now. And so different approaches have evolved somewhat still. We do see them centered around applications made prior to first bloom, rates ranging up to a pint or so, and then applications up to a pint and a half thereafter on 10 to 14 day intervals. Now, some approaches, particularly under well-managed, irrigated situations, we might initiate applications at the early square stage, maybe nodes eight to nine or 10, and then follow up those applications like we would others on weekly or bi-weekly intervals, up to say a pint and a half break. But these are the dominant ways that the product is used today. Now, I mentioned stance being a somewhat different product. It is, again, mepiquat plus plant hormone, and it's thought to be a little more forgiving in the plant, and therefore you're not likely to be too aggressive and shut the rate down, but its application would be relegated primarily to this range of two to three ounces at the early bloom stage or perhaps at the early square stage. It's a premium price product, and so frequently those applications would be the first applications, and then thereafter we would, most farmers might switch to a more standard mepiquat formulation just because of cost. Now, just a few comments about how to think about PGRs, and I'll underscore that the point think, maybe do it several times in our discussion, there's not an exact recipe. It's cut and dried, it's not that way. We've got to adjust as the season unfolds, as plant growth and development unfold, as weather unfolds, but the real goal is to make squares, bowls, seed and fibers, and a good fruit set means the plant's moving towards reproduction, reproductive production, not as opposed to vegetative production. So that's a good PGR, that's a good effect on the plant that sort of encourages the plant or puts a load on the plant to minimize or to at least slow down vegetative growth. A second point is that once plant tissues, leaf and stem tissues have fully expanded, you can't shrink those. So we're using mepiquat chloride to affect newly elongating tissues, be that leaves, be that stems and internode lengths and so forth. A third point is we think about fertility, we think about irrigation in rainfall as being a way to push the crop, but then some would think, well, maybe we can push the crop at the same time, hold it back vegetatively and apply breaks, if you will, with mepiquat chloride. It's not a quick and easy way to high yields, but it is a way we think about particularly well-managed high-input situations. Now, a fourth point is that I often hear people agonizing over rates. Oh, do I use six ounces or do I use 10? I don't think it's that fine of a system. So it's not that delicate in most situations, but I would admit there are infrequent times when we really can't recover from being too aggressive too early or not being aggressive enough or soon enough. And having said that, though, I would perhaps say that timing may be more critical than rate. We make and do something a little earlier that we can't do later with much higher rates. So just a few philosophical approaches and thoughts as we consider different initiations and rates and so forth. So how do we know when to make the applications and how do we know about rate? Just some factors that we'd consider, certainly weather, current and future, that you got to make some prognostication about what the weather's gonna be in 10 days to two weeks out. What's the variety like? What's the situation in the field? Does it have a history of aggressive growth or not? Do we have a good situation and we expect ranked growth? We would adjust and approach that situation accordingly. We'd also consider such things as fruit retention, whether the presence or absence of crop injury and how late it is in the season. And then the specific row pattern. So these are some ideas. Certainly variety is an important consideration. Does variety X or Y? Does it grow ranked? Does it grow aggressive? Does it grow tall? That's a valuable piece to factor into the equation when we're thinking about what we're gonna do, how we're gonna do it. Now, most cotton folks, farmers, consultants, county agents and others would have a program in mind, but you gotta adjust as the season unfolds. And I would say if there are 40 cotton folks in a room, there are 57 different ways that they would use picks or 57 different programs that they would come up with. But when should we be more conservative or should we be more aggressive? I've listed some things here. If we're in a season of extremely high temperatures, which often coincides with a lack of rainfall, again, maybe we wanna dial it back. The load of fruit, a good fruit set and a heavy fruit set I think occurs with most of our varieties that we have today except maybe where we see lost to plant bugs, early squares lost to plant bugs. But I think these were situations that might cause us to be a little more conservative. Likewise, there are very few situations in the Southeast where we can grow crops solely on irrigation. So if it's a high temperature year, even if I've got a irrigation, center pivot irrigation, I still might be more conservative. Just can't sustain extremely good growth on center pivot irrigation when I'm not getting any help from rainfall and temperatures are extremely high. This would also apply if we've got a situation where we're watering with the cable, so they may only have surface water in one or two or three applications per year. In a non-irrigated situation, a rain-fed situation, I'm always gonna be a little bit conservative because you don't, 10 days out, we could be extremely different in terms of being hot and dry and the plant be stressed. On skip row patterns, I put a question mark here. My thinking is when we have skip row situations, we want the plant to grow to canopy over the gaps. I don't have a lot of data to support that, but that's just my thinking is we wanna be, we wanna be a less aggressive with our PGRs because we want the plant to grow. And likewise, if we're recovering from herbicide injury. Now, some situations where we might go the opposite approach, it's a, hey, we need to be a little more aggressive than our standard thinking. Let's say conditions are extremely good for growth. Let's say temperatures are topping out in 85, 87 degrees and we've got good soil moisture. Cotton's gonna grow extremely fast in that kind of situation. Likewise, if we've got a very rank and aggressive variety or if we're in a field situation or a year when borax particularly troublesome for us, we might wanna be finished with a crop that's a little shorter than in some other situations. If we have poor fruit retention, we know there's gonna be a lot more vegetative horsepower in the plant so we could be a little more aggressive with our PGR rate. Likewise, if the calendar's getting late, there is some evidence that we can support and encourage early fruit set and limit vegetative growth so we might dial up our rates. The final point, again, I put a question mark because I don't have a lot of data, but my observation is that the nematode resistant varieties tend to have greater stock health late in the season and therefore there may be a little late season growth from those so maybe we need to be watchful with those situations and those varieties. Now, just some factors that we might assess plant growth and development and think about when do we start or when do we make the next application and at what rate? The first thing is a very subjective one is, hey, what does the crop look like? Is it growing fast or is it not? That's just an appearance thing and some folks won't taller cotton than others. The latter three, the other things are more objective. You can measure and make some counts and make some assessments here that would support whether or not, hey, this crop is really growing fast. The first one is height to node ratio and we would take a measurement of plant height. We'd take the cotyledon and that we would measure from the cotyledon nodes to the terminal and get a height and then we would count nodes. Again, the cotyledon would be node zero and we would count to the terminal node and we'd have a crop stage reference point that gives us some measure of what we should expect, what's normal and what's aggressive or not. An example I put here is say we've got a crop at first bloom and we measured at 28 inches with 12 nodes, 28 divided by 12 is 2.3. It puts us right about here. We're tending on the aggressive side. So again, maybe we need to initiate or accelerate our approach with PGRs. A similar method is one I think is very valuable at the early bloom stage and that is counting nodes above white flowers. This would specifically be first position white flowers. If we're running at five, six or seven, we need to see more growth. We don't need to slow it down too much with PGRs. Conversely, if we're seeing nine nodes or more at first bloom, boy, that plant is super aggressive and we need to dial it up and maybe increase our rate, certainly intervene with PGR. But so these two methods reflect node development and I think are valuable tools. A third way is to specifically look at the inner node link of the tissue that's the most recently fully elongated and that would be between nodes four and five down from the terminal. If we counted the terminal node as zero and then counted to nodes four and five, that plant, that zone would be what we would evaluate. And some people would measure it, say two and a half, if it's two and a half to three inches or if it's three fingers or four fingers or something, somebody would again use an idea that is a gauge. If it's greater than this, you know, hey, it's the plants really stretching out and we need to do something with our PGRs. And so that's just another way to support the decision-making process when you think about rates and timing. Now let me finish with a few questions. Again, to pride our thinking about this because there's no exact automatic, this is concrete how it is. Number one, can we push for bigger yields by being stomp in the gas with fertility and irrigation and then holding the plant back with our PGRs? Even from the earliest introduction of PICs, that was the thinking. And it's just not that simple and that automatic. So it just doesn't work that way. But I would say that under our high-input situations that the PGRs are very valuable and integral tools for us, but it's just not the simple way to big yields by stomp in the gas and stomp in the brakes at the same time. A more practical mundane question is how rain fast is Mepplequat chloride? Many of the labels would suggest four hours. If we're in a rainy period, we're getting occasional showers and we're concerned that we might wash it off. It's very soluble. Then we could add a non-unction factor and that would probably reduce it to one to two hours. So that would be an important practical consideration if we're in a rainy period. What about tank mixtures? The labels have lots of information about tank mixtures, particularly does it physically mix? My general observation has been that the Mepplequat products really don't add phytotoxicity to our tank mix approaches that we use. So it's a very innocuous tank mix partner if we wanna use it that way. But consult the label specifically about physically mixing the different product that you might have and you might use. Fourth point is, can we grow good cotton without Mepplequat chloride? And I'd say the answer is yes. I would qualify on high input irrigated situations where we know we're gonna grow aggressively. Yeah, it's gonna be an integral tool, but in a dry land non-irrigated situation where we're getting good rainfall, good growth, but a great fruit set, it may not be just, yes, it's just not an absolute essential. But again, these are the Mepplequat products are important tools, but it's just not an absolute necessity to grow in cotton. And then finally, what about the late season cutout applications? Can we make more cotton with those? It certainly makes logical sense that, hey, we could reduce vegetative growth and maybe put more photosynthetic product into bowl, seed, and lint development. The data just don't support that in terms of yield increase. Yes, the late season applications do a nice job of leveling out the crop canopy. They certainly make it look prettier and probably give some assistance with mechanical harvest. We don't have a rancor plant that we might otherwise wind up with. But in terms of, again, does this make us more cotton? Most of the time it does not. Does it maybe reduce our problems with regrowth? Again, not always, but it's a good idea, a good thought, but it just hasn't been demonstrated in a consistent yield production. Again, these are some of the questions we finish with. This is a thought process to explore. And hopefully this helps you as you look back on how the product has been used over the years, its mode of action of the different use patterns that have evolved and some of the questions we've examined together. So again, thank you for your attention in this webinar. Hope this is of use to you and maybe replay it as we get into the PGRU season in mid-summer.