I'm Ryan Miller, crop extension Educator earlier this morning. We recorded in an episode of the Strategic Farming Field Notes program. Strategic Farming Field Notes is a weekly program addressing current crop production topics. A live webinar is hosted at 08:00 A.M. on Wednesdays, throughout the cropping season. During the live webinar, participants can join in the discussion and get questions answered.
An audio recording of the live program is released following the webinar via podcast platforms. Thanks and remember to tune in weekly for discussion on current cropping and crop management topics. We welcome you here to the program. These sessions today are brought to you by the University of Minnesota Extension with generous support from Minnesota farm families, and also from the Minnesota Soybean Research and Promotion Council, as well as the Minnesota Corn Research and Promotion Council.
With that, my name is Dave Nicolai. I'm University of Minnesota Extension Educator in Field Crops. We want to welcome our guests this morning. Dr. Tom Peters, Tom's Extension Sugar Beet Wheat Specialist, working with both the University of Minnesota and North Dakota State University. And he's at his office at Fargo this morning. And Dr. Bob Koch, extension tomologist in soybeans at the University of Minnesota as well. Let's take any more time.
I'm going to start off here and turn the program over with Tom and Tom. It's certainly been an interesting year. We had, I think almost like the month of August occurring in the month of May. This year we're extremely warm, hot, at least for some of us that are used to a little bit cooler temperatures. Certainly I think some of that might have confounded weed biology, Weed management and that type of thing. I know every year we talk about the spread of weeds and so forth.
But before we get into all the herbicide business, let's talk a little bit about some of our weed problems that are typically with us every year. And some of them are more challenging in situations with an environment like this. The two that come to my mind, and you might have others and talk a little bit about that, of course, is water, Hemp, and Kosha. It doesn't really make any difference whether you're a sugar beet grower or not. It affects all of us.
What are your observations in looking at that in terms of biology and some of the problems that we ran into this last year? Yeah, let's Dave, thank you. It's a privilege and an honor to be on this morning. One of the first things about biology that I like to think about is when does a weed germinate and emerge? The textbook says that Kosha is one of the first weeds that emerge in the spring. It did.
We saw a lot of Kosha, especially in northwest Minnesota, but also in west central Minnesota right after planting. I would argue in some of our fields that Kosha was the first thing to germinate. It germinated ahead of the wet. It germinated ahead of the sugar beets. But the other thing that we observed this year about Kosha is when it got hot in May and June, it went dormant. We didn't see as much of the prolonged germination and emergence that we sometimes see.
I attribute that to how warm it got and the increase in soil temperatures. Water hemp is a little bit of a different story I think this year. And I'm going to make a bold statement, Dave. I don't think water hemp was as bad across the state in 2023 as 2022. And the reason I say that is, first of all, there's some areas of the state that got good rain right after planting. The Pre worked. The Pre were very effective on water hemp.
Then the rapid growth of our crops, again attributed to the soil, to the air temperatures, we had tremendous early season growth of our crops. I think that to some degree, helped to shield away from water, hemp germination and emergence. Then also May and June were pretty dry as well. In a lot of areas, especially with water, a seed that grows off the surface or 1 " deep, usually in response to rain events and temperature fluctuations.
I don't think we had the flushes of water hemp that we had in. Other years? Well, I would agree, certainly. I know in some of the places I traverse in Central and southern Minnesota, we had really dry conditions. We had moisture early to help the crop. And that late April, very early May, and then we just turned off the faucets, so to speak, some places for 3456 weeks almost. And I think that really did affect the amount of water hemp with that. What's your recommendation?
Should we be complacent and say, well, we didn't have much of a problem and we should be good for the rest of the year in the next couple of years. But not really that's the case, is that no, we need to actively manage weeds year round again. We have to worry about the biology though. One characteristic of pigweed is the seed becomes viable very quickly after flowering. You only have two weeks. I want our audience to keep that in mind.
If you're out there pulling weeds, carry them out of the field, because if you throw them on the soil, they're going to finish making seed. And you're going to have to deal with the seed for four to six years. Carry them out if you're going to mow them off, feel good about mowing, but realize that some of the seed that's more advanced is going to make seed or some of the water hemp is going to make seed. Now Dave Kosha weed and lamb's quarters are different.
Those weeds require more of a full season to make viable seed. So going out and mowing those in August is perfectly fine, and I think you will reduce the amount of weed seed production that you have. So I would encourage our listeners to actively manage all weeds, but feel good about managing the second batch because that seed isn't viable.
At this point, I know we don't have a tremendous amount of acres of small grain and bit wheat, but are there some things about the stubble and that crop coming off and subsequent weed growth in those areas that you've seen? Well, I work with a lot of small grains growers in Northwest Minnesota. Unfortunately, we have a lot of weeds this year in our wheat. That gets back to the earlier comments I made about Kosha coming up as fast as the wheat.
We're already talking about post harvest management strategies. Whenever we're talking about post harvest, we've also got to be thinking about what next year's crop is going to be and incorporate those into our decisions. But yes, we absolutely will. We'll try to manage weeds that are in our residue combination. I think you hinted to this, even besides the dry weather, you felt comfortable that where we got some moisture, that our Pres did a very good job across the landscape.
Yeah, Pres are always an interesting conversation, so some people sometimes say they didn't do a darn thing, it was a waste of money. And I think the performance of Pre is usually attributed to rainfall patterns. If you got rain on your Pre in a timely manner, I think they work very effectively. But here's the thing, Dave. The worst thing about a pre herbicide is, especially in 2023, is if you made the application, everything you did was correct.
But if you didn't get rain, you might have gotten a good rain for ten or 14 days after application. But that may not have been time wise adequate where water help may have germinated and emerged before that. Even though you did eventually get rain, the rain came after some of the earlier weeds started to germinate and emerge. Really knowing when that event, that rainfall event occurred in relationship to the weed biology is really critical to truly evaluate the performance of pre.
Let's just visit a little bit about sugar beets. I know it's very preliminary obviously in a lot of your observations, but a lot of fields that I looked at, at least for the Southern in look fairly clean. Some not so much as others, but where they made a good attempt, I think things work very well. What are your comments about the sugar beet crop and coming in here for this year?
The same. I learned from Alan Dexter many years ago, that plant as early as you can, people, the farmers that were able to plant the last week of April, April 30, and then the first few days of May early. Planted fields look tremendous. And oh, by the way, they got rain at the end of the week and that really helped the weed control as well. But I think we have a very nice crop out there, and it's not just sugar beets.
Dave? I think across the board in my travels, I'm seeing a pretty nice crop or crops. But one thing, about 20:23 we're only two weeks away from a train wreck. So we're going to need to continue to get rains because we don't have a lot of excess rain or a lot of excess moisture in the profile. That's for sure. I know that we're down compared to a year ago, probably 20 or 30% in terms of qualifying as adequate. Let's just re summarize this recommendation for this fall.
We indicated that probably the hardest weed to deal with is water hemp because it's going to go so fast between what I call, if you think about like the dough stage, to physiological maturity of that water hemp seed. That's very quick. I sometimes I get questions from growers say, well in this crop or this area, what if I apply a growth regulator, herbicide or 24d? Will that affect the viability and so forth? And I think that's really problematic.
You might have more options in some of these other weeds, But when it comes to water hemp, you can't wait too terribly long is that correct? That's exactly correct. I think at this time of the year, and I'm talking about water hemp that's in some of our low growing crops like sugar beet or soybeans. Really the only good option we have is electricity or hand pulling by electricity, I mean using the weed zapper.
One of the things that we've learned about the zapper is we've already experienced the yield loss that's already there. But one thing the zapper does do is it stops the physiological maturity process. In seed, it'll reduce the amount of water hemp seed that becomes viable and mature as well. That's one option that we have. The other thing that we can do is manage water hemp after we start taking the crops of either using a fall herbicide program or possibly using tillage or other means.
Let's think about 20:24 What lessons did we learn about we control post emergence in terms of timing, what things worked, what are some things we need to keep in mind for that? Certainly, if we're in a sugar beet rotation, we have a number of years here, but we've got to leverage that summations that you observed. Again, I know it's very preliminarily, but what are some things we need to keep forward and keep in mind for 2024? Yeah, a couple of things that I learned.
The first one is sometimes we hear about non performance where products don't work. And I'm going to use an example in Sugar beets, Peters, I went out and used Ultra Blazer and it didn't do a thing. My knee jerk reaction is, yeah, the water hemp was too big, but that's not fair.
I think if you see an example like that where you don't feel you got the performance that you needed, you might consider saving that seed and sending it into Dr. Serene or myself to test that seed to determine if there might be a weed resistance challenge going on. I guess I've always viewed weed resistance as somebody else's problem. Yeah, we've got widespread resistance with ALS inhibitors and glyphosate, but by and large the other products all work. I'm starting to doubt that.
I'm starting to wonder if weed resistance is becoming more widespread, especially with the oxen, especially with the PPO inhibitors, especially with the Group 27. Dave, the other thing that I learned, I'm reminded all the time that agriculture is a continuous set of activities that starts with planting and ends with harvest.
Well, one of the things that I didn't realize, or I failed to realize is how dry it was in 2023, especially in August, September, and October, we didn't get a lot of breakdown of the 2023 herbicides and then add that to the late spring that we had heck in my front yard in Fargo, I had 2 ft of snow on 15 April. We didn't get any herbicide breakdown in the spring. The combination of the events in the fall combined with the spring I think reduce the breakdown of some of the products that we had.
And that resulted in carryover in some places. So those kinds of lessons and learning about how last year's products can impact this year's crop or this year's products and next year's crop, I think is a real important message for our listeners. Well, thank you Tom. I hope you can hang on. We might have a question or two as we go forward. So it's a good opportunity, like we said, to get out, take care of those field edges, approaches, fence lines and so forth as we go forward here.
And that we see situation with that One last message, Sugar beet, pre harvest will start on Monday. All right. So there'll be a lot of trucks on the road. Everybody be safe out there when you're out on the highways. Sure. Sign of fall there in terms of that summer is coming to an end. But Bob, we're not quite done with this insect situation here. It just keeps coming up and so forth. And we think, well, the month of July is over. I guess we're all done.
But not necessarily When we talk about soybeans and other things, it's weather confounding. I know you've called around a little bit, I was at Farm Fest this last week. A number of growers, we're talking about that. It's not every field. What are some words to the why, so to speak, that you might have a little bit about where we are on soybean aphids and what should we be doing across Minnesota. Yeah, thanks, Dave. In terms of what we should be doing, we should definitely be scouting our fields.
There's a lot of variability out there. I think a lot of that depends on how the rainfall patterns shook out for different parts of the state. Areas that got some decent earlier rains, seems like that's where we're seeing a lot more soybean aphids right now, especially. And a Southwestern Minnesota. Central Minnesota, even into Northwest Minnesota. I spoke with Aaron Lorenz, our soybean breeder. He has some trials up in Crookston. He had to get his plots treated for aphids.
I was down in Lamberton this week and setting up an insecticide trial. We had well over 1,000 aphids per plant. It's a pretty big aphid year in some spots. But it's certainly not all areas, not all fields, areas that are a little drier have continued to be dry, are still looking at issues with spider mites. And we know those are a very challenging pest under dry conditions. What are some of the concerns or dangers here of pulling the trigger too early?
We know that aphids can develop an opportunity to move from field to field. But what's the downside on beneficials and just lining to be like from an insurance? Well, I'll think because my neighbors do it, I'm going to do it. Maybe talk a little bit about that. Yeah, you bring up a couple of good points, Dave, and I think they tie into the biology of this insect. The first is the movement.
Around this time of year, we often see these slab aphid populations developing wings, and then they can move to new fields. When they're moving to new fields, they're often looking for some of the later planted fields that are not as far along developmentally, those are going to be really attractive and not only attractive, but more suitable where the aphid populations can grow faster. That movement can be triggered by different things. Can be triggered by the quality of the slab plant.
Maybe there are too many aphids there. And then those aphid mothers can detect that they'll produce a generation of babies that will develop wings and fly away if you have a field that's not necessarily heavily infested. Now, that can change in a short amount of time when you get these winged aphids migrating into a field and reproducing. The other aspect that you mentioned are the natural enemies.
These are predatory insects like lady beetles or these tiny parasitic wasps that attack the aphids. These wasps lay their eggs inside the aphids. The wasp eggs hatch and then the wasp larvae will feed inside the aphid, killing it. And then the wasp merges, flies away, starts its life cycle over again. But what they do is they leave behind what we call an aphid mummy, which are the dried, rusty, puffy remains of the aphid.
The fields we've been sampling around the state, we've got very high levels of parasitism by these parasitic wasps. And it seems like in some areas, these parasitic wasps and the lady beetles might be holding the aphid populations in check. We're reaching maybe 100, 200 aphids per plant, but they're flat lining there. They're not continuing to increase. But there are clearly areas where the aphids are outpacing these natural enemies. And sky rocketing to much higher levels.
Again, you can't just assume that you have no aphids or you have tons of aphids. You got to get out there and scout your fields and really get a feel for what's happening in each of those particular fields. We're backing off some of these high temperatures this week. We're back in some places up north '70s, but typically in the '80s, that's still pretty prime temperature, is it not, for aphid survival at this point. At least going forward, it looks at the next two weeks.
Yeah. A lot of us like to think about it, that the temperatures where we're feeling comfortable outside in the '80s, that's where aphids are doing really well. Once you get up into the mid '90s and higher aphid reproduction starts slowing down, they don't do as well. It might have been those high temperatures earlier on this summer that we're slowing down aphid populations.
Now, as you were saying, David, we're getting some somewhat cooler weather and this could be really good aphid growing weather. Not only are we getting that movement or redistribution of the aphids among fields, but once they get into those fields, temperatures are looking pretty good for them to grow quite rapidly.
I've talked with Bruce Potter over the years and so forth, and a lot of things come back to you keep going out there in the field and watching because things can still be a problem all the way up until R five soybeans. Any comments there? Yeah, we recommend scouting in using the threshold at 250 aphids per plant through the R five growth stage. In doing so, you're going to protect your yields from losses caused by the aphids.
But what you're also going to do by scouting regularly and using that threshold is prevent some of the more challenging later season decision making. We know that based on some data from some of my colleagues in Minnesota, that infestations into early R six can sometimes cause yield loss if they are much larger. Infestations probably above, well above the typical economic injury level. That's a really tricky time to try to make a decision to apply that insecticide.
Hopefully, if we're scouting, using the threshold before that, we'll be putting ourselves in a better situation. Well, some of these newer products and pre mixes and so forth that we have to be careful about. If you've made one application ignoring that field, things can come back and you've already taken out the beneficials. There is such a thing as movement as a continuing problem, is there not? In terms of some of these fields, depending upon how they're managed.
If they were applied much earlier in the season. Yeah. Dave, you can have movement to the aphids and recolonization after an insecticide treatment. But I think two things I want to bring up. One is insecticide resistance. Keep in mind that we still have pyrethroid resistance soybean aids out there. We've documented it now over multiple years. Pretty much across all of the soybean growing regions of Minnesota into the neighboring states as well. Manitoba, the Dakotas, Iowa. Keep that in mind.
If you're applying a pyrethroid, you want to get out there and scout after those applications to make sure the insecticide did what you wanted it to do. You mentioned mixtures, Dave. It seems like these mixtures are still working quite well. Even the mixtures that contain a pyrethroid, they're still doing pretty well, even though the aphids might be resistant to half that product.
Right? But one of the challenges I think, with the mixtures is if we go in with a mixture on our first aphid application, if we need to come back in for another application against aphids or mites or something else, it limits our options, right? Because you've already gone in with two different insecticide groups probably. And we don't really have all that many total insecticide groups available to us.
So just keep that in mind as you're thinking about your arsenal insecticides and how you might rotate through them. Well, I think that's oftentimes the case and you might mention a little bit about we can aggravate or flare that spider mite if we don't get rain here in some places. No, it sounds like a pretty good chance of some rain Thursday night in Friday. And I don't know over a lot of Minnesota that situations with that.
But even a normal rain, Bob isn't going to alleviate and wash off the soybeans, is it not? I think we have to make a comment about a rainfall doesn't negate the problem here. Right, Dave? First, so you mentioned aggravating the pest populations. One thing I want to mention, if you've got a field that has mites in it, keep in mind what insecticides you're using. A lot of the pyrethroid insecticides could make that problem worse. They can flare the mite populations.
If you're targeting spider mites, things like birn, there are some other mid, remind me what the other part of the question was. Basically in terms of monitoring there, that it can be a lot of variability with the rainfall. That's right, Yeah. Yeah. In regards to the rainfall when those Saban canopies are closed and pretty thick and lush, they can provide a pretty good amount of protection there.
Right. So if you have a pretty huge storm at this year with a thick canopy, it might knock the aphids down a little bit, but I wouldn't necessarily count on it. I think you'd want to get back out there and scout again. I think of that kind of weather impact a little earlier in the season when the canopies are more open, you get the hard driving rain and some winds. I think Ian Mccrae has shown that that can knock the aphid populations back. In terms of spider mites.
Um, I also would not count on a decent rainfall necessarily knocking their populations back. I think what the more important factor is there is a good period of time with high humidities to favor the fungal diseases that knock down the mite populations. Not necessarily one or two rainfalls, right? And I know even in the area and eastern part here, they're only talking about a quarter inch of rain, possibly on Thursday night. Really very negligible.
But just last thing, on the soybean Aps, keep in mind that you mentioned some areas of Western Minnesota that were heavier with a populations but, you know, more here on the eastern side of the state. We haven't seen that as much. Now they're picking up maybe in the Southeast, but we had a lot of variability. We had soybeans that were planted and sat in the soil for 345 or six weeks before emergence. So even in soybean crop, it was up and down. Up and down, and we were dry.
But interesting to see how that comes out. But the bottom line is, we haven't seen the pressure. You can't always paint with a broad brush, right? And I think that's certainly been the case from what you've seen from there, and even on St. Paul campus. I know we've looked around and I haven't seen as much either in terms of that. Yeah, David, you know, that all gets back to getting out there and scouting the field. There's a lot of variability out there this year.
If I can take just a couple seconds here. So want to mention that in talking with Angie Peltier from Crookston, she there's quite a bit of a green clover worm larvae in some fields, so that might be something people want to start paying attention to in some areas. These are small green caterpillars sounded like they're in their early in stars, very young caterpillars yet. But as they get bigger, their consumption of leaf area can really increase. So these are defoliating insects.
We've also got grasshoppers out there in pretty high numbers in some areas. Just another reminder, something else to be looking for when you're scouting and keep the thresholds in mind for this time of year reproductive stage soybean in Minnesota, we're still using the defoliation threshold of 20% Look at multiple plants across the field. Some leaves from the top, middle, and bottom of the plants average all those levels of defoliation.
Then if that field wide average is above 20% that's where we would recommend starting to line up an insecticide application. Some folks might be hearing about some lower thresholds, ten to 15% reproductive growth stage is a soybean, but in Minnesota, at the University of Minnesota recommending the 20% threshold. Okay. Great. Well, we've been through a lot of communication here this morning on some important issues, both weeds and insects. Tom, you've had a little bit of a break there.
Any last thoughts that you have on from a weed science perspective that we did not address that we should mention here as we close? No, I don't have anything else but thanks for asking. We certainly have that and we'll have and so forth coming out. And Bob, I know that we have some other events coming up here with Bruce Potter, Lambert in the end of August here on corn t Worm. Our new insect specialist, Fay is on staff now there.
And we're also going to have another event, probably at N Rosemont area on September 7. We watch for that for a field days. Dr. Dean Melk as well. We'll have an opportunity to address those as well. I'll just put a plug in for the crop news. A couple of articles that you've been involved with, Bob and Bruce and other people have talked about soybeans, spider mites. If you didn't pick up everything that we're talking about here, I'll refer back to University of Minnesota Crop News.
Finally, Tom, I'll put in a shameless plug for an article that you and I were involved with in the Crops and Soils magazine on herbicide resistance. You can get it online. If you get the magazine, a Certified Crop Advisor, or whatever, take a look at the most recent edition of Crops and soils. And it gives a good overview here of what we're dealing with in the upper Midwest. With that, at this point, I have another question here.
I'm going to segue back over to Dean Lb, because it's more of a disease one, and save Bob of being a plant pathologist here this morning with that. But we want to thank both of you for taking the time out of your schedule to be a part of the program again. And so we'd like to also just to capsulize here.
The sessions were brought to you by University of Minnesota Extension, University of M Farm Families, Minnesota Soybean Research and Promotion Council, along with the Minnesota Corn Research and Promotion Council. Thank you again for your time and thank you for attending.