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May 30, 2018. Jeff Gunsolus discusses early season weed management.
Hosts Anthony Hanson, Dave Nicholai, and Bill Hutchison at the University of Minnesota alert growers, ag professionals and educators about emerging pest concerns with Minnesota Field Crops, including corn, soybean, small grains and alfalfa. They offer useful, research-based pest management solutions.
Dr. Anthony Hanson, IPM Educator - Field Crops
Dr. Bill Hutchison, Coordinator of the MN IPM Program
Dave Nicolai, Crops Extension Educator & Coordinator of the Extension Institute for Ag Professionals
Good morning again. This is the second in a series of podcasts from the Minnesota Extension IPM program at the University of Minnesota where we are focusing on a variety of pest management issues this spring and early summer for 2018. Last week, if you had a chance to catch it, we talked about black cutworm given the high numbers of moths coming into the state as detected by our trapping network. We talked to Bruce Potter about how that trapping system has been working this year and the concern that we have with late planted corn. In the past few days, we have some reports of cutting happening in young corn in both Dakota County and Rinville County this past year.
Bill Hutchison:We would encourage growers crop consultants to continue to scout for black cutworm and the cutting activity that could be happening right now throughout Southern Minnesota. Today we are really happy to have Doctor. Jeff Gonzalez with us, an Extension Wheat Scientist with University of Minnesota and Professor of Agronomy, to talk about some of the current concerns with weed management, herbicides, herbicide drift, etc. That are a very big issue in this state as well as much of the Midwest. Our primary host today will be Dave Nicolai, again joining us, Extension Educator and Coordinator of the Ag Professional Program here in Minnesota.
Bill Hutchison:We also are happy to have Ryan Miller with us today, an Extension educator based out of Rochester. So welcome everybody. And Dave, I think you've got a lot of good questions for Jeff. Look forward to the conversation.
Ryan Miller:Well, you, Bill. Appreciate the introduction here. We're recording this podcast in the morning on Wednesday May 30 and as Bill indicated I have my co worker here Ryan Miller out of the Rochester area and he's been involved with struggling to get crops planted down in that area for research and educational use. We're going to talk a little bit about that and his experience and the weed growth, but before that I wanted to introduce a very good friend of ours in terms of Ryan our working relationship. I guess basically we want to introduce our boss Doctor.
Ryan Miller:Jeff Gonzales and Jeff you want to just give a little introduction on your background if some of the folks don't know how long you've been here at the University of Minnesota and what your current job classification is and job duties and where you spend your time.
Jeff Gunsolus:Dave, spend my time in a lot of areas but as an Extension weed scientist I've been here since 1986 so I'm working on over thirty two years in Minnesota, working for Extension and being a professor here at the University of Minnesota. As far as job duties, it's both Extension and Applied Research in corn soybean weed management. It's been focusing on that this entire time. As you alluded to, I am the supervisor, the program leader, if you will, for the crops team, which has 10 regional educators, two of which are on this podcast and another eight around the state. That and a communications person that we do a lot of our web and podcasting work through.
Jeff Gunsolus:So it keeps me busy. I'm not bored.
Ryan Miller:Well, I don't think we're going have a problem with that this past week. I'm sure your phone has been ringing or probably will ring a little bit more here as we get into the weed control season, so to speak. Ryan is up here from Rochester and Ryan last night I know that in the Dakota County area we had an inch and a half of rain in the last twenty four hours talking with one of our climatologists across the hall from us today in the Soils Building they indicated that Dodge County had over three inches. So a lot of people had a lot of rain. I know down the Martin County area they're probably just thankful that they want the rain to shut off for a while.
Ryan Miller:Other areas of the state though were dry but it seem though the rain was widespread. What's it look like in Southeastern Minnesota in terms of crop growth and weed growth and what are you presently seeing and having to deal with?
Speaker 4:Well it's been a really challenging spring as far as the frequency of precipitation to get field work accomplished in terms of planting and herbicide applications. On the flip side of that, we've seen herbicides that went on really activate well in terms of the pre emergence herbicides and so had pretty good weed control where people managed to get planted and put on their pre emergent herbicides. It's been very good when fields have been planted as far as the crop growth. We've seen during these warm conditions really robust and fast crop growth. But unfortunately that then couples with the fields where due to the precip we had to prioritize planting over herbicide applications and now we're stuck without pre emergent herbicide on in those weeds like the heat and humidity just as much as the crop.
Ryan Miller:Jeff, we've talked for years about the need and the benefits from pre emergence herbicides. Is this another year for book, so to speak, where it's really been valuable? Where do you see it from your perspective in terms of rate of adoption and is it working like it should and what are some things that people should be thinking about here the balance of the spring?
Jeff Gunsolus:Well, rate of adoption of the pre emergent herbicides initially the twenty first century, if you will, really took off first in corn as people realized that early season weed control was really significant for corn yield because of nitrogen competition primarily, but it's also now really picked up in soybeans. I think last indication we were at about 80% adoption rates in soybeans as well and to be honest with you, I think the driver of that was our applied research was out there. People could see the benefits of the pre emergence herbicide, but the real driver was we have, especially in soybeans, real challenges with weeds like waterhemp, giant ragweed, common ragweed that are resistant to multiple classes of herbicides. So in a way the pre emergence is absolutely essential to get off on the right foot.
Ryan Miller:Well, let's jump ahead. We'll talk about a couple of weeds, but you know, one that is a problem across the state and it certainly has been increasing not only in the Western area but in the Eastern and now in the Southeastern area is waterhemp. Right. Now both yourself and Ryan have been involved in some of the supplied research but if folks are dealing with waterhemp and it haven't positively identified in their fields in the past or looking at it this spring, what are some strategies that they should think about from pre emergence application and some options here, particularly in soybeans as well as post emergence options here as well and thinking about and dealing with a possibility of glyphosate resistance and other resistance that might be encumbering there. So let's center a little bit on waterhemp right now and talk about that because it's starting to come on and we expect obviously more in the future here in the next couple of weeks.
Jeff Gunsolus:Well Dave, the big driver here with waterhemp is it does like heat and we've supplied that now. And when you add the soil moisture with that, they will start really emerging and growing quickly. Actually, you could expand that to all the weeds under these temperatures, the growing degree days or such, they'll really take off. But you know, the real issue which separates waterhemp from a lot of other weeds that we concern ourselves with is a lot about its duration of emergence. So once it starts it could easily go well into July, even into early August as far as emergence.
Jeff Gunsolus:So one of the big issues here is simply the fact that if you have late planted beans or corn for that matter and you do not have good canopy closure, start to lose that shading potential. So you're going to need something with some residual activity down to get some good weed control. So one of the challenges Ryan mentioned is across the board here is we have places like Rochester along the I-ninety Corridor where it's been very wet. Delayed planting going on, but then we have places up north where it's been dry. So you've got all across the board with different scenarios and different concerns.
Jeff Gunsolus:So dry weather is an activation issue. Good news is it's not a wasted treatment. When it does rain, the herbicides will activate. You will get weed control over the weeds that are targeted for that specific herbicide. The thing that will happen though is if you're getting emergence before that activation really takes hold, you're going to be doing an early post emergence weed control.
Jeff Gunsolus:And remember this always, what we've learned from all our research, there's less penalty for erring on the early side of weed control than on the late side. I'm going to flip weeds on you now Dave. Think of lamb's quarter, early emerging weed.
Ryan Miller:It's already pretty large.
Jeff Gunsolus:It's already pretty large. So then you'll have a whole cohort coming up that are really small. The small ones with a lot of your post applications, you'll target and do well. Those large ones, they might not be that impressed. I've seen that down in Ryan and Lisa's plots in Rochester on a regular basis.
Jeff Gunsolus:So these timing issues then really come into play. So it's really a challenge the post emergence across the board always remember this simple rule with any of the weeds four inches or less and really from a growth stage to reduce crop injury potential, reduce weed crop competition, and to also improve the efficacy of the herbicide. Generally, you can target V4 corn soybeans as well, that's the ideal. We know weather and time gets in the way, but that's what we're shooting for.
Speaker 4:So Jeff, guess kind of the common question now, we in Southeast waterhemp start to emerge around May 20 and just kind of start emerging. How does a grower go about assessing the risk of herbicide resistance within in their waterhemp populations in terms of the Group 14 and glyphosate resistance.
Jeff Gunsolus:It would be really nice to know that ahead of time, Ryan. Generally, this is where you look at adding the group, if you can still put a pre on, or if they're not emerged, the group 15s, the duals, warrants, outlooks, that type of chemistry, that sort of is a really sustainable, been a good player as far as, and a lot of them are package mixed with other types of chemistry. So, you know, one of the things if you're still looking at that, that's an option. And the Group 15s can also be put on in a layered approach with a post emergence herbicide. So if you're out doing an early post with Liberty or with glyphosate, then putting that on with the group 15s, you're getting the weeds that are up hopefully and you have some residual weed control.
Jeff Gunsolus:Unfortunately, this knowing the population of which resistance and what isn't is, you you can have all of the above in any given field. Some could be susceptible, some could be resistant. So that's a real challenge, right? I don't have a super answer for you in that regard. In post emergence, when you're going that way, then again mixtures of sites of action would be the way to go.
Jeff Gunsolus:In corn you have the group 27s, the pigment inhibitors like Callisto, that type of chemistry that you can use. You have the Dicambas in corn and you can use the Dicambas now in soybeans early post emergence as well. There are some other options.
Ryan Miller:Another thing that's happening with the weather right now, Jeff, is it's been very moist, it's been very warm. Warm obviously in germination we can talk about the weed seed bank a little bit later but for some of our soybean growers that have may not have had the opportunity to get that pre emergence on in a timely basis Not everything is equal out there in terms of the labels. Some of them are rather restrictive within three days of I believe it's an emergence and so forth and what you have from a timing standpoint. Without getting into specific labels, there some general rules that people should think about if they have been out of the field and can't get back in and now the beans are popping out of the ground and so forth? You know, we can really run into some trouble here in terms of perhaps soybean entry.
Jeff Gunsolus:Right. A couple of things. One is in general, the group 14 herbicides, the PPO inhibitors that are soil applied like the Authority Group, and then also things like Optil, Sharpen, chemistry that has a lot of the Group 14 chemistry in there, you have three days after planting, or more importantly is to know if you start to see the soybeans emerge, especially at the crook stage or above, and you put those herbicides on, you could kill the plant or at least severely reduce that stand. The exceptions to that are things like Anthem Max and the Fomosafein products like Prefix, that sort of chemistry. You can go in that window, you have a little more wiggle room, but the limiting thing there is a little bit more on rate and geographic location as far as impacting carryover.
Jeff Gunsolus:So one can always default to saying this, Dave, read the label before applying, okay, but when all the pressure's going on, that can be a real challenge.
Ryan Miller:Well that's certainly true given the fact that some of our listeners may be in Central Minnesota or Northwestern Minnesota, sometimes outside of that magical line of I-ninety 4. Right. Those labels are restrictive and some things as you mentioned you cannot do. Right. So you have to know, first of all know where you are in terms of that in the label, really read closely with that.
Speaker 4:So yeah, you actually brought up something that I talked to a farmer last week and there was a little bit of confusion around a term that we often throw around, are your soybeans cracking? His idea of what that is and what it really is, was different. He was talking more or thinking more along the lines of as the seed starts to swell and the pateletons split, it starts that initiation. It doesn't really refer to that, does it?
Jeff Gunsolus:No, it's more about exposure of the plant material to the herbicide itself. But you know if you start to see that, those hypo coils just starting to crack out of the ground, that could even be dangerous because think about if you were unfortunate enough, you sprayed it and then you got a heavy rain, washed it into the furrow, you know, some bad things can happen there. That's what makes this all so tricky even in this podcast conversation is hopefully we're talking to an audience that's all across the board in the state and we're trying to talk about all the different scenarios. Too dry, too wet, late planning, everything's working fine because I got the pre on just right and it's all activated. So the challenges are there.
Jeff Gunsolus:The one thing I was thinking about over the weekend when it was so hot, hot and dry also can create issues especially post emergent herbicides as far as, and we may be hitting another hot trend here, that's why we want to also keep our windows of application on smaller crops so we have fewer issues. A lot of the systemic herbicides, those that move in the plant like dicamba and like glyphosate, those sort of things. If it's under stress, the plant's under stress, the weed is under stress, it may not be taking it up and moving it around in the same way. Whereas on the other hand, something like Liberty, Liberty's highest effectiveness is under hot conditions, hot and humid, good uptake, a lot of sunshine, and it really works well.
Ryan Miller:Well, brought up one product here. We want to spend a couple of minutes on that and that of course is dicamba. And we think about our crops that have the trait, particularly soybeans, as well as other crops though that they can actually spray over that. But, you know, we've had some big changes in that labeling in Minnesota. And can you summarize briefly what growers should be thinking about this year?
Ryan Miller:I mean, in terms of the late planting and still getting the crop up, but we have that label that's still out there and especially in Minnesota, we have some special precautions. So let's just summarize some of those and some cautions and so forth and where it would fit best and where would not. I'll try Dave. I'm not going into the great depth of the label as you mentioned. I think most people have had the training, they understand the wind, the buffers, all of
Jeff Gunsolus:these other restrictions. I'm just going to focus on the 24 C aspects, which are the add ons, if you will, to the Minnesota requirements, which is a June 20 cutoff date for the application of Dicamba on soybeans, for those products registered, and also the other is the 85 degree temperature date. Let's just look at the June 20. Some people are saying, you know, this is going to mess me up because I really would like to put it on a little bit later. But the weeds, if we, as we got done talking about, are really coming up, they're really emerging.
Jeff Gunsolus:All the buttons are pushed Dave for effectiveness on small weeds, so really this June 20 date I don't consider an impediment to doing what we have to do. The dicamba should work very well, in fact its strength is on the weeds like the lamb's quarter and the ragweed species, kochia, if they're not resistant. And then its actual inherent weakness has always been waterhemp. So actually going earlier in June is going to be a better thing for you than going later. But you will have to keep in mind that it doesn't have a lot of soil residual.
Jeff Gunsolus:So you will still need these residual type herbicides that we're talking about.
Ryan Miller:We're getting kind of toward the ends of our podcast. Ryan, do you have any last points or questions for Jeff or things that you would like to bring up? I know that you're going to be having a opportunity for hands on training in a field day coming up here in early July, is that correct?
Speaker 4:That's correct Dave. So you'll get a chance to visit with Jeff and see some of what's going on in terms of weed management trials within the state. In particular, we're talking about the crop management tour, that occurs in Rochester at the research plots on July 3 this year with an 08:30 registration time. So, mark your calendars. That's the date we've reserved for an opportunity for farmers and ag retailers and and and such to come in and look at some of what we've done in terms of trials and some of the results there.
Ryan Miller:Well, very good. I know that kind of in closing some farmers may be distressed at those giant ragweed and those lambs quarters that came up early Jeff and are out there but now the pre has been activated and starting to work but is there still opportunity to do something and it's fairly large you know four, five, six inches but should we cash in our chips and leave the farm at this point or is there still a future here with those two weeds?
Jeff Gunsolus:There's always hope, Dave. There's always hope. You know, in corn, I think you have some really good post emergence options that can still be played out. Again, when you're into the situations in soybeans, some of your best go to's are still your, assuming resistance isn't an issue, your glyphosate or your Liberty, depending on your technology, then you just basically have to adjust the rate and the adjuvants to act accordingly. And there is always this tool that you can use.
Jeff Gunsolus:It's called a cultivator, and this tool is being used more and more in the state of Minnesota. And again, I think in these places it's in response to some of these resistant weed issues where they, especially with resistance, trying to go for zero threshold seed production to get their weed seed bank down. And so I'm encouraged by some of the abilities to adopt a little more flexibility in addressing some of these. There's always hope.
Ryan Miller:Well, that note, I think we're going to close our program for the day. We appreciate again having our guest co host here Ryan Miller from the Rochester Regional Office on hand with University Minnesota Extension and of course our featured guest Doctor. Jeff Gonzalez with University of Minnesota Extension, a wheat scientist in corn and soybeans. So this is Dave Nicolai concluding the second in our series of Integrated Pest Management. This will also be available on iTunes along with the first installment with Bruce Potter and we talked last week about black cutworms.
Ryan Miller:If you missed that you can go back to that particular one and pick that up as well. So we'll be featuring these in a number of different commodity groups and organizations. And so with that we will stay tuned and next week I have another important topic in Integrated Pest Management here from the University of Minnesota. Thank you.