 Hello everyone, welcome to this edition of the Alabama Cooperative Extensions Alfalfa in the South online series. My name is David Russell, Extension Weed Specialist, and today I'm happy to be discussing Weed Control and Alfalfa. As you're probably aware, there are many benefits to growing Alfalfa in the South. High yield potential, forage quality, and versatility. I know many of our Extension Specialists will be covering several of these topics as part of this series, so if you'd like to learn more about these topics, please check those out. Amongst other important factors, variety selection is also key. Variety development has made big improvements over the last several years, and many of our land-grant institutions conduct official variety trials on these. Lots of data are collected such as yield and quality, winter hardiness. I also want to point out that there is available the winter dormancy scale, so as you choose through the many options of specific varieties for your location, depending on where you're located within the state, this winter dormancy scale will be important. I know I'm only scratching the surface by the few varieties that I have listed here, but just wanted to bring attention to what is available. This information came from the University of Georgia, and I know many other land-grant institutions make these variety trial data available. So you'll also notice in these lists are an RR attached to many of these. This signifies the Roundup Ready technology, so depending on whether you have this in mind for your production, that may or may not be important. Again, there's several requirements from an agronomic standpoint, and again, many of our Specialists will touch on these, such as soil tests, which are absolutely necessary. Alpha has poor tolerance to low soil fertility. Many of you are probably aware that alfalfa needs well-drained soils. Alfalfa is capable of developing a deep root system, and you'll notice stand declines after several years if the adequate soil conditions aren't right. Ideal pH is usually between 6.5 to 7. Alfalfa is pretty sensitive to acidic soils. If you'll be making frequent cuttings in a hay situation, adequate phosphorus and potassium are absolutely necessary. And what I'd like to touch on today is proper weed management. Again, like the other factors, there are many requirements when it comes to weed management. As many of you are aware, the establishment period is the most critical. I know many of you already have established stands, but if you are just thinking about trying alpha production, please understand that this part is really critical, not only from a weed control standpoint, but agronomics as well. If you're familiar with any other established stands that have failed over time, there's really no good receding options for partial stands. And this is due to a chemical process that we call oligopathy. This is basically root exudates that come out from the alfalfa roots. Many other plants and weeds have this. It's basically a defense mechanism that tries to help that plant survive. We want to reduce weed competition at planting. That's part of that establishment period. Fall is typically preferred across Alabama and much of the south. There's many factors that play into that, but from a weed control standpoint, I contend that the warm season versus cool season weed spectrum is highly important. You'll see the preferred fall and planting windows for wherever you are as part of the across the state. And again, I can't stress enough that a establishment period, if you are thinking about starting a stand of alfalfa, I like to think of it kind of like the difference between corn and cotton. There are many ways that we might adjust cotton agronomics once cotton is planted to get a preferred outcome. But if you take corn, for example, once you get corn in the ground, you've already selected your variety. You've put out your nutrients. You've adjusted your soil, so you're pretty much set to the end yield production. So please just do your homework on the front end and keep these factors in mind. Preplant weed control, and this is for the monotypic stands where we're talking about establishing alfalfa alone. This is either in a prepared seed bed or no-till. So we want to start with a weed-free seed bed. We don't want to have competition like this top picture where you're in the summer months, we're getting a plethora of annual grass or broadleaf seedlings competing with established seedlings of alfalfa. So starting that prepared seed bed, if it is in a conventional tilled situation, we want to control those emerge weeds with something like a non-selective option. These options are typically roundup or grimox on. And keep these two in mind. If you do have an established stand, the roundup and grimox on are labeled in season immediately after cutting. So please just read the label if you're thinking about those in established stands. But again, in that establishment period, we want to control the perennials especially, cultivate, and then plant into a firm seed bed to get that seedling off to a good start. There is, like I mentioned earlier, the roundup ready alfalfa that is available. This is a good option for weed control. There is no soil residual. And so if your crop is tolerant to roundup, it's going to control many weeds in various seasons. So take for example, if we are drilling or planting in the fall, we're going to wait till that crop gets going and we're able to spray over the top if we have an abundance of weed species that's giving that alfalfa some competition. It is a little expensive initially, basically the seed cost. So it's probably not a fit for most. It's also not a good fit for a bermudagrass mixture. So I know many of us have heard of drilling or establishing alfalfa rows into an established bermudagrass sod. And this is a versatile system that is productive for many, but being roundup is non-selective that kind of limits what we can do in this system as far as weed control because obviously the roundup is going to injure the bermudagrass stand. There is potential for herbicide resistance and I want to make those of us that are considering this, I want to make us aware of that. Again there's no soil residual so the over reliance on roundup is a concern. As you probably are aware, roundup was developed in the early 70s. For a while that was kind of the silver bullet. It made weed control really easy. Then the resistance issues began popping up just a few shortly years later. This was due again to the over reliance on this product to do all weed control. It wasn't until about 96 that we saw the first genetically modified crop and once again weed control became easy. So I want us to begin thinking of how this relates to alfalfa. In these of resistant crops we at least learned how to incorporate tillage practices to combat weed pressures. So my point is if you are familiar with or have or are considering roundup ready alfalfa please be careful with the over reliance of this product. We want to incorporate an integrated management approach just like any other management system where we use tillage whenever possible or mix up our herbicide mode of actions or simply allow the alfalfa to close canopy and to compete with a lot of these encroaching weeds. So again talking about alfalfa establishment in addition to weed pressures we have a different weed spectrum depending on when we're planting in the south or in particular Alabama. In the fall we've got hot weather as you know that October time frame is probably one of the most dryest period that we have. Typically the we run into a drought. I know we have the last couple seasons so rainfall is far so that's going to inhibit what how our stand gets started. We also got insect pressure as the temperatures are still high and we haven't yet gotten frost the insects are still out there so keep that in mind. Compare that to the spring planting. You know the last couple years have seen heavy heavy rainfall and that results in poor soil conditions and I know in the northern parts of the state we're still facing potential freezes at this at this point. I think many of our other specialists will kind of lean on the side of that fall planting window and from a weed control standpoint I much rather control or have to deal with the cool season spectrum versus the warm season spectrum. We get many of the aggressive growing grasses like foxtail and crabgrass that begin to encroach during the spring versus those small seeded annuals and broadleafs like chickweed and geraniums and stuff like that that germinate in the fall of the year. There is an option for pre-plant weed control. This is one product is Eptam. It controls annual grasses and broadleafs but it's pretty pretty application specific. We don't want to use this if a grass or a grain nurse crop is used so it's really only for a monotypic stand. With this there must be optimal growing conditions again falling the south is usually hot and dry. If you have a known population of problematic grasses and broadleafs this may be used. The key is that it needs to be incorporated. First mechanically and then for optimal control it really needs to be incorporated by rainfall. So after you apply it either in a granular form or spray it needs to be tilled in or cultivated in that top layer and then ideally we need to have a rainfall pretty soon thereafter because this is a volatile compound and it will disappear pretty quick. So the ideal rainfall is usually about a quarter to a half inch. It's really isn't a good fit for many at establishment because it is really finicky and so application specific but it is an option. When we're talking about inter-seeding no-till into an established bermudagrass stand please be aware of herbicide carryover and what do I mean by this if you have a bermudagrass field whether it be a permanent grazing pasture or a hay field try to remember if you've used it in the past or the previous landowners or you are operators see if they've applied any herbicides like Grazon Dext or Grazon P plus D or Cimarron. These are soil active herbicides like piclaram and aminopirulid or metzulfuron or dicamba that may hang around in the soil a lot longer into the subsequent growing seasons that would negatively affect crops. You'll notice the top picture here this specifically is the piclaram that is damaging a following soybean stand. You can see the cupping of the leaves and the epinasty the twisting of the stems. A good way to see if your fields will potentially damage the alfalfa stand and just to check to see if you have herbicide in that soil a bioassay may be necessary and what do I mean by that that's typically planning a sensitive broadleaf crop like tomato into the ground where we're thinking about planting alfalfa and within a few weeks if that tomato plant is still growing fine chances are there's not a lot of herbicide or any herbicide in that to damage alfalfa so if the tomato plant does find more than like your alfalfa will too. Again going back to that cool season versus warm season weed spectrum you know we think about things that are germinating in the fall we're in grazing situations usually dealing with Italian or annual ryegrass the annual blue grasses the little barleys the small seeded annual broadleafs like chickweed or geranium or the mare's tail hopefully a lot of our perennial grasses and broadleafs will have been taken care of at this point in that burn down application prior to planting so hopefully going into the planting situation we're only going to be facing a control situation from the annual species and like I mentioned earlier we've got a plethora of warm season annuals that will be germinating in the spring and this again is the difference between fall and spring planting so I would again argue that the warm season weed spectrum would be much more difficult to control versus the cool season. There are several options here that are listed as post-emergence applications for seedling alfalfa so once you're planted and the plants begin to come up look in the notes section and please read and follow all label directions I know this is a large list but I just wanted to highlight a few two four DB particular you may be aware of this one from using clover and pastures it's generally safe on legumes it is however weak on chickweed it's best applied to broadleafs when they're under about two inches and after alfalfa has reached about the third trifoliate leaf you'll notice that many of these herbicide recommendations state that you shouldn't apply this until alfalfa has reached a certain growth point so this is usually after about the third trifoliate leaf and that just will ensure that the plant is up and going it's got an actively growing root system and that it will tolerate many of these herbicide applications over the top. Bramoxanil is another one you may find this one under the old trade name buctral I believe the registration has expired on this one it's got little soil residual activity the soil half-life on this one is about a week that's mainly due to microbial degradation so subsequent flushes of any broadleaf weeds really won't be controlled from that initial application on either of these 24db or or bramoxanil you may see some leaf tip burn that would be similar to applications of liquid fertilizer but it typically would grow out of that pretty quick on a lot of these you may find some crop injury that's unacceptable when the soil when the air temperatures are high usually when temperatures are cool is the more ideal time to apply these and again that would lend preference to a fall application as we enter kind of that cooler growing season. Kerb is another one this is a Dyn Nitroaniline herbicide a DNA if any of you are familiar with Prowl H2O in our grazing pastures and hay fields this would be that same mode of action we get optimal control when applications are made between 50 and 60 degrees and again just like Prowl H2O this needs rainfall in corporation it's absolutely necessary that after you apply this we get rainfall and what that does is just work that herbicide into that top layer of soil it kind of creates a barrier for preventing any weed seed germination this again will cover will control certain small seeded broadleaves and annual grasses. Raptor is another one that's good on weeds like mustards and pennycress and shepherd's purse I want to point out a couple of our germinicides as well as the roundup non-selective again these are not fitted for an interceded production into a Bermuda grass stand these are grass specific and they will injure Bermuda grass so just keep that in mind what I'm talking about here is mainly for monotypic stands of alfalfa but I do want to keep in mind that many of our producers do intercede this into grass stands here's just a quick rundown of some control measures some data from Oklahoma State on some of our chickweeds and henbits mustards and annual grasses these weed control ratings again the seedling stage is the most important outside of the roundup ready crop if you have grass weed pressure I may lean toward the use of select or post and then for the broadleaf activity depending on your goals and your operation and your budget it may just come down to a cost between a lot of these herbicides that are listed again if you've done the proper prep work initially at getting your field ready and cultivated and a good burn down in place hopefully many of the perennials will be taken care of I'd say if you had to pick one of these herbicides with some grass and broadleaf activity outside of roundup pursuits a pretty good option it is safe on the games it is a little bit pricey but if you're left with just the annual broadleaf spectrum I'd say just an application of 2-4-D or Bermoxanil may do just fine at some lower cost now this short list that I have right here is in addition to what I've already mentioned for the alfalfa seedling stage but these here these five are just available for established stands in other words stands that have been planted more than a year and have gone through their first hay cutting there are a couple of these that for sure do not need to be applied ombre mutagrass just like the last list and these are AIM and Chateau the carpentra zone and flumeoxazine flumeoxazine these will damage the Bermutagrass stands you'll find metribuzin under the name trichor or many others this is labeled as a pre herbicide and again applied in the fall or winter after dormancy to control annual grasses and broadleafs there is specific wording on this label that allows for use in mixed grass stands but there is a caution however that rates greater than about one pint may thin the perennial grass stands this may be desired to lower the competitive nature of grass to allow preference for Bermutagrass alfalfa growth but depending on your operations you may or may not want to use that at rates that exceed one pint. Velpar is another one I really like I like this one in grazed grass it is a photosynthesis to inhibitor it has good soil activity many of you in south alabama who have had permanent pastures infested with smutgrass velpar is the option for smutgrass control and here we have it available in alfalfa use for alfalfa it needs to wait until dormancy because it will cause some damage to alfalfa so again here's where that dormancy scale on particular varieties come into play depending on where you're located across the state again if all you really have is your common small seeded broadleafs and grasses then metribusin would be a good option or you could include that with grimox on for emerge weeds and this mix is on the label so please again please read and follow all label directions we have harvest restrictions available too I mean I know many of you are know that these are important so in other words the pre-harvest intervals for all these herbicides there is a waiting period between the time of application until the point that you're harvesting for hay or grazing for forage so there's a haying and grazing restriction on many of these I know I've thrown a lot of information out at you but I will again point to the alfalfa ipm guide this is available at asus.edu you can find this particular one and many others for different crops on this website again if you've got any further questions or interested in any other information please check out our forages facebook page or alabama forages or you may contact me directly thank you