When Pests Bite Back

Dr. Tom Peters, Weed Scientist and Sugarbeet Agronomist with U of MN Extension and NDSU, discusses how irresponsible herbicide applications could backfire, and several pre-harvest strategies to prevent waterhemp escapes from replenishing the seedbank. Also, be sure to consider glyphosate-resistant volunteer corn when managing herbicide-resistant weeds. Bruce Potter, U of MN IPM specialist, discusses the status of soybean aphid populations, and the value of using the economic threshold. Other insects discussed include spider mites and corn rootworm.

Transcripts are auto-transcribed. If you need more accurate transcripts of an episode for ADA purposes, please contact Anthony Hanson - hans4022@umn.edu.

Well, good morning, Everybody and i'd like to welcome you today is to strategic farming field note session, and we're going to cover today.

One test bite back. So again, these sessions are brat you by extension and generous support from the Minnesota, Soybean Research and Promotion Council and the Minnesota Corn Research and

Promotion Council. I'm. Liz Stahl, Extension Educator.

I work out of the Worthington Regional Office focusing on crop and moderating with me.

Today we have Claire LaCanne. She is an Extension Educator and Rice and Steel counties,

But a different spin on things we're gonna have a couple of polls today, too.

So those of you that are participating live can answer those questions and those that are you that are listing on the podcast will kind of at least be able to explain what what people here i'm joining us live today. had their thoughts on But anyway, So with that I

just wanted to turn it over to our first topic today again when honor test fight back, we're gonna look on the on the weed front, and so we have Dr.

Tom Peters either extension weed scientists and sugar meat specialists.

He works with *su and University of Minnesota.

But first of all, if you want to put up that first poll and i'll see if our readers are well, people can see see that.

Okay, So the first question is, we have 2 questions of this poll first one is, do you think it weed resistance to any of the following on land you farm or the land that you work with?

And here you can select all that applied so we've got like like the seat ppo inhibitors, so like luxury, cobra als inhibitors like pursuit.

First straight Hpd inhibitors like Callistol and lattice.

I was fascinated. for example, liberty or at chazine or other, and the last option is No, I don't think so.

And then there's a second question onto this too, so just scroll down in your screen.

This one's asking what is the most common glyphosate resistant weed in Minnesota.

We've got koso water have common ragweed, or glucose that resistant volume tier corn, so we'll give you just a couple more seconds to do this, and then we'll close that

out.

We would go about 60. Okay, 2 more seconds. Your choices here and you wanna close that out.

Diane can share the results here. Okay, all right. And, Tom, you can take a look at this.

I will let you review the answers to how that fits in with what you want to talk about today.

But well, i'll i'll help you out a little bit yeah, we see glipacy.

It's the number one for resistance to the following at 68% of the people.

And then 20. Some percent of the als 27% say no, I don't think so.

We have some people 18% with Ppo inhibitors.

9% of the fascinate and 5% with atrazine.

So, and the most common weed going to services. we in Minnesota was water. Hemp people are reporting was 77% to volunteer corn phone and 27%.

So. Tom, i'll turn it over to you I know you have some things to share, or started with liberty.

Liz i'd like to start with the first question.

So i'll make comments regarding this when I go through my pictures for those that are listening.

Participating this morning. I would like to make a comment about liberty, though.

So 2 people mentioned liberty and possible liberty, resistance.

I would encourage both of you to reach out to your regional educator, and first tell us where you where you live.

And second, if possible. I would like to get a whole of a a sample a seed sample possibly to test that i'm not aware of any liberty resistance in Minnesota but that doesn't mean

anything. So your observations are very important. and and If you're seeing some things that are unusual, we certainly need to to hear about him and and and see that so i'm gonna put up a a a a brief

Powerpoint presentation, and i'm gonna talk a little bit about water hemp resistance.

So. if if I query my colleagues in different parts of the country, and ask them what herbicide families have you observed resistance in?

We get usually 6 families. so can you put that in presenter mode. we're just kind of seeing a small picture of that.

I thought I did sometimes it's kind of funky on.

Let's see that's not in presenter mall just a second.

I'll try it again. Did that help at all that helps I know what i'm I I know what I forgot to do

Is that better? There you go. Yeah, that looks good. So 6 families and I mentioned that that some of these are in Minnesota.

Some of these are not in minnesota but but the scary thing that weed science to concern theirselves with is sometimes we'll have the same planned with multiple herbicide resistance.

So in Minnesota I think it's very possible that our water help may have resistance to als Inhibitors Group.

2 group 9, and the ppo inhibitors all in the same plant. So that's that's pretty scary.

Now what I don't see a lot of is liberty resistance, and as I started with i'm not aware of any liberty resistance in in Minnesota and Eastern North Dakota but I wanna I

wanna challenge everybody. I think liberty has to be our special it's the herbicide that we very carefully use in crop production to ensure that we don't have widespread resistance.

So what that means is is, save it for one crop in the rotation.

The one crop that you need or value liberty the most in.

And then second, use liberty in a program, use it in conjunction with soil.

Residual herbicides use a layering technique, and then save liberty for weeds that are less than 4 inches tall.

If you're using it post emergence I call that application in June.

Maybe early July liberty the closer because it's right at the end of the use label.

No, I I do a lot of driving during the summer my my territory sugarbeat growers in Minnesota and North Dakota, and that's quite a few miles between these guys.

So I get a chance to drive by a lot of fields.

So I was observing a Soybean field, and in mid-july, towards the end of July Water, Hamp started to poke. God of this field and Liz, If we get a chance, we can talk.

About Why, that might be occurring, and I I just you know I just made a note, boy.

There's there's water hemp in that field well guess what.

2 weeks 2 weeks later, in the last 2 weeks those water hamper, brown, and or at least the leaves are brown.

So what I think is happening here is. The producer went out and sprayed the field.

Probably because they were worried about seeds. that so waterhap is a prolific producer of seed and i'm guessing, the producers said, I don't want any of that going to see but 2 things all we're doing here

is burning off the leaves we're not going to kill this plan. it's too big.

The plant in the picture is at least 2 feet tall so we're gonna see regrowth here.

But this is exactly the recipe that weeds take for developing resistance.

They take advantage of maybe an awkward application, and we identify, maybe a very rare plant or population of plants, and those are the ones that proliferate.

They're the ones that are able to survive and that's how resistance develops.

So. so, Liz, I would encourage our our producers that are on the phone or l listening to this podcast, later to resist the urge to use liberty when you're copied the value.

The chemistry, and for hand weeding, or excuse me for late escapes.

I would consider other ideas for for eliminating those escapes, such as hand weeding.

I know it's hard work I know it's still hot out.

But that's the kind of activity we have to do to preserve our chemistry.

Yeah, really good point time. And you know on your hand weeding, what do you think I mean?

Cause we get questions sometimes. Do we need to remove the weeds out of the field?

Or you know, a little key to just pull him and leave him lay.

But you know at what point do you think we're getting viable seed, and I mean, do we need to worry about hauling them out of the field.

Very important, very important question. So so here's the deal with water him water, hemp, seed is viable in 14 days.

2 weeks after it. flowers, so I don't think we know for sure when it flowered.

But if we're, going out there now this week the the week of the eighth of August would encourage everybody to carry him out of the field, bring a bag, carry him out of the field throw them in a burn barrel or something

but don't just drop them because there's going to be a fair amount of viable seed there already.

So. yeah, you probably you probably helped yourself. but you've gone through all the work to pull them.

Carry them out of the field Now, if you're pulling out common ragweed or lamps quarters those those plants make viable seed much later in the season. so I wouldn't have any problem at all just pulling

the common ragweed and letting it go. Good reason why we have a lot of water.

Humphrey well and you know in tackle a bit about water in, but I don't know if you're ready to switch gears a little bit. but I i'm just intrigued by this

question, too. We asked what's the most common glory for this, and we of Minnesota.

77% of people said, water him. but volunteer corn came in the second at 27%.

What's your take on this time Well, first of all there's a tremendous amount of volunteer corn out there, and and it makes sense, because I I think much of the the seed. Co.

Much of the corn we plant has the glyphosate trade in there.

So. I think a lot of our programs combined life isate with other things, and we're not getting it with glyphosate.

But but here's the thing I think was we're using the the group one herbicides.

But in many cases they're in combination with the group 4 herbicides, the oxen herbicides, and I don't care if you're using a dicampa program in soybeans or 2 ford colonel

you you're gonna get antagonism mixing together Dwight.

Mixing together. select Max, for example, and one of those oxen herbicides is not the most effective way to get volunteers.

So the guys that are going through the work and and and and putting a herbicide out there are probably not realizing the the results that they're expecting no good good points, and you know to again when we're looking at

this point, as i've seen these weeds poking through the fields.

Really what what can we do? I mean? what what would you recommend what's what's kind of the process at this point we talked about hand weedy.

I mean, is there anything to do? or should we just pretty much take notes and plan for next year?

So so. so 3 things lives so first of all we're done spring

I know we like to spray things it's fun to move our sprayers through fields.

But is not the solution anymore. So let's put the sprayer away, especially for our roll crops.

Number 2 I mentioned hand. weeding and i'll say it again. Go out there, and especially in those heavy pockets in the field.

Go out and get those number 3 there's a few people that are using the weed.

Zapper. We just saw some published information from missouri where they're telling us that the weed Zapper not only fries the plant, but it is also reducing the vability of the seed that's in the process of being

made by the plant, and and then you mentioned a good one and I'm not gonna let that one go away.

Getting good maps, especially at harvest as to where the most severe weed infestations are in fields makes a lot of sense to me.

Yeah, that's. one thing that we've asked about it like our private has a site applicator recertification workshops in the in the past, and it's it's kind of surprising how few people actually report using

weed maps, but I mean I think that's a could be very useful.

Don't you think just to help target what products you should be using in areas.

Maybe you need to find between rates for example or where you're gonna really try to hit it hard.

I just seems like a kind of underutilized tool.

Always like to say that we know exactly where the weeds are until we harvest, and then we do tillage and our.

You know we have this big empty field again and we're not exactly sure where those weed areas were

Our software products now are so good at at giving us location.

Specific information. Take advantage of that, and draw some maps, and those those are records just as valuables.

The yield maps, in my opinion. Well, and and one last question before we switched over on the insect end.

But so if i'm a far away, you know and we're getting close to harvest, and I see this kind of water have forest coming up, Should I just run my combine right through there, or come come back later and and I think

we know the answer to this, but yeah I i'd prefer that First of all, i'd say wait as long as you can with that field.

Do the the fields that have less pressure first, and then if you can go around those areas with with heavy weeds

In many cases you're compromising yield there anyway, especially in the most severe areas.

But our combines do a tremendous job of spreading that seat out, and I would. I would prefer that we don't allow that to happen, or if we do, do, that, let's do it at the end.

And make sure we're cleaning our equipment when we're done.

Excellent points. Thank you, Tom. claire i'm gonna turn it over to you.

Yeah. And I wonder if we do wanna address the question in the Q. A.

Quickly, just because other people may be curious to Tim.

Can people submit waterhead or gray weed samples that they believe have ppo and glyphosate resistance?

And if so, can you kind of tell them how to do that?

Yes, you can. So what I would encourage you to do is to reach out to your regional educator or county agent, and we'll be sure either our educators or agents are in contact with myself.

Or Dr. Dublin syringe, my colleague at the University of Minnesota.

So Dublin especially is taking a lead at trying to map out where weed infestations are especially resistant weeds, and he'd love to hit Devlin and his team would love to get those samples.

Thank you. Thanks. Yeah. So now we will transition over to our insect topic.

So we're going to hear from Bruce Potter our Integrated Test management specialist at the Southwest Research and Outreach Center in Lambertton.

Thanks for joining us, Bruce and Diana.

If we could launch our poll we'll start off with our insect Poll here. So we're asking about Soybean aid.

So how do you decide when to spray for Soy being aphids?

And you can select all that apply and our options are.

You use the economic threshold? you believe 258 fence per plant threshold is too high.

You spray When custom applicators are in the area you don't scout us spray when your neighbors do he spray a fence as a tank, mix and herbicide or fung aside you spray once the

soybeans reach a particular growth stage or around a particular calendar date, or you spray when you're agronomist or crop consultant tells you, too. There's 2 more options Yeah, so to the scroll everybody and you

do not spray and thensect aside for so I mean if it control at all, or you don't plant.

So I being class you don't farm

I'll just give a couple more seconds here

Alright, Diane, I think you can. Yep. Thank you.

Share the results. So we see that the largest number here, 52% of our participants today use the economic threshold, and then kind of our second largest number.

We see 14% believe that the threshold of 250, if it's per plant, is too high, so they spray earlier.

So first of this, there's anything else you want to point out and the results or comment on that

I'd like to talk about a little bit of spring

If is a take mix with an herbicide or funds aside.

And then people, I think that 250, if it per plant threshold is too high.

You know it. Car crop prices are high this year, and people haven't had there's pretty many aphasis for the past couple of years.

Populations are a little bit up this year. and and you know, I suppose people have been waiting for a couple of years wanting to kill Aids, and now is their chance.

And I think this cai crop rice. Why,

Falls into things, too, in that you know they're worried they're gonna lose yield these aphids have no idea what how much you're gonna get from bushel It's not that they eat more when

prices are high and they eat less when the prices are low.

That that 258, and per plant threshold is pretty darn and conservative, has been for a long time.

It gives you some some opportunity to like the time in there to get things.

Those populations controlled so I know there's a lot of fear, and and angst about not getting things sprayed in time.

But you know I don't I don't think it's. I don't know the threshold is not is not too too high.

It's maybe people's perception of how much time they have to get things done.

Those sorts of things i've heard people this year worried about without Lars van wanting to use a ground rig, and they want to spray away.

That canopies open. guys want to mix it with a fungus side and and save a a trip.

The problem with that is and you know most fungi size for sprayed a week 2 weeks ago.

Right Now we're right in the middle of a of If it's moving between fields we're getting if it's as these big plants quit growing vegetatively, we got a lot of those events that

were up on the top of the plan those producing wing nimps. Those are winged wing defense. Those acids are dispersing within the field throughout fields, and you know that insecticide's gone by now or a

lot of it's gone. so your timing timing issue might be a little bit of a a problem. if you're doing a tank tank mix just like spring corn worm beetles with corn

fungicides. So the other thing that happens if you're spring and insecticide and the fungi side without regard for how many insects you've got out there is you are knocking

out both, possibly some beneficial fungi and some insect predators, and as as if it's moved into the field, flaring Athens or flaring spider mice.

If if you've got some hot dry weather

So don't do it Well, that kind of leads into a question from a participant.

Here is I've been waiting on I started being fun just side application. as long as it felt I could with the goal.

If needed, I would tink, mix, and set aside with that application.

Is there a problem with that? Well, I mean if if if you're waiting in and waiting till you have aence.

There's not a problem. and if you're but if you're gonna throw the ins if you don't have a I I think you could save a little money and and some potential risk by keeping the

insecticide out of it. so you've got some time on the fungi side.

Especially if you're in one of these drier areas there's not much there hasn't been much phone to leaf disease out there.

So there's no reason to be real proactive if you've got a weight weight mold in the field.

You're trying to manage those sorts of things and Then You'd want to have that bunch of site on a lot earlier.

Thanks. Yeah. And and back to this sorry being a vid application or with the threshold of 250 aprons per plant on 80% of the plans and a typical year that gives you about a a week.

To react. right, Bruce. And so with high prices this year, maybe that windows a little bit shorter.

No, it's not the th the the timing still about the same. because it's not that that 250 acids per plant causes yield loss immediately.

The those if it have to feed on the plant for a while it's a concept of 8 for days, or how many if it's you have for how long?

So There's there's there's a there's a leg in there, and we don't have real good data on this further along.

Those plants get into as far as Further along.

Those plants are in development, probably the more aphid they can tolerate.

So bigger more mature plans can probably take little North Pacific.

It, feeding them to a small early reproduction like this stage plan.

One thing I want to mention on these if it's in 250.

Some guys may think they've gotten burned by waiting till 250, and the problem might not be the threshold.

It might be Scott scouting. I mentioned a lot of aphids have left the field right now.

But they've left some if it's below in the lower canopy, and over the last week some of those small white aviation they leave behind have been reproducing real well one day I was looking at stuff

we'd skeleton last week and some of these adult is, if it's in the lower canopy head up to 12.

Well, Nms to him, so those populations can can really explode lower in the canopy.

Those acids are smaller down there and they're hard at the spot. so make sure if you're scouting you're not just looking at the top of the plant anymore.

You've got to look at. Look further down yeah good suggestion We have a question about spider mites.

How are the population so far this year we're just starting to see some some injury levels in the The past week in these more droughty areas or past couple of weeks in the drought the areas pretty

isolated even in some of the draw stressed areas of spider mice have been pretty low.

And now we've had some rain and some dues some cooler weather that should tamp the spider might down.

But there's plenty of time if you have things heat up, and and you run short of moisture again for those populations to to pop back up.

But the rain really, and the weather is probably helping us out right now.

Kind of going back to Evans, because I just saw this question pop up.

But could you make some generalizations about the aid?

Populations like kind of across the States over all this year.

There. Athens are like a lot of insect problems or insects.

We have this year whether it was army worms, cutworms.

Grasshoppers. spider mites they're there, but they're spotty they're not real uniform.

And so initially, it was a lot of these small fields, the block surrounded by trees.

Some of those got treated. Minnesota River valley, and and you know, is in and and into the south central part of the State.

We've got some higher populations but again. it's still mostly smaller fields. at Lambertton.

Here we're pretty close to threshold but then you go a little bit.

A few fields away some of the larger fields, and you know, or either pretty rare, or still out low population.

So they're there. but I've heard of issues up into West Central Minnesota as well, but it seems like they're still It's not like the early days of Aphans.

Were we'd have these big waves of aid infestations moving through the State.

They're still they're still pretty scattered do you have any information, Bruce and if any of these populations kind of that, you're seeing across the State are looking like they might have some resistance to pi rays and you know that's been

kind of on our minds. the last couple of years is seeing some resistant populations.

So i'm assuming they are they have they haven't it hasn't gotten any less.

We still they'll pick them. up in a research boss or or when people people try a breath rate, there's still some fields that have issues it's not every field by any means.

But it's a large enough percentage of them that spring a straight breathe rights. pretty risky

We'll see what happens this year but my guess is it's it's it's stick it's fixed in the population.

What do you recommend for people If they suspect that they might have a resistant population or a past of that

And now that clerk or peer passes out of the picture, apparently, what what do you think people should do?

We've got we've got some alternatives. It's a lot better situation than with spider mice.

We've got some alternatives we've got some group for insecticide savanto and transform.

We've got Sophia. those 3 are all pretty specific to sucking insects.

They do a good job on efforts. You need good coverage just like you do.

The perthoids they're translocated to a to a certain extent, so it so.

But we've had pretty good results in in field and fields, and especially in our insecticide studies.

So those are an option if you use a breath right You're probably gonna have to mix it with a neo-naick at next annoyed or you're gonna have to mix it with one of these other

products. There's some repackage things like rich back which has got transformed in it in a freezroid or or Renaissance, which is Sophia, with with the breath right the reason for the truth right

is to broaden the spectrum out. you know.

For some reason people are all confused when they spray if it's.

If the efforts are dead, they don't want to see grass stoppers, or anything else out there.

You know I guess I guess i'd i'd be more focused on trying to take care of the pop problem at hand.

You've got a few grasshoppers but if it's so.

Your problem worried about the Athens. you don't have to worry about killing a few with grasshoppers out there.

Business need to eat, too. Thanks for saying I know we're running cool, Since is there anything you wanna add quick here?

Clear they're running near the end I know we But just that we did put in the chat a link to some information on insecticide options, for so I didn't do especially with hybrid ride resistance on the horizon, so that is in

the links, and I guess I just say any last part in thoughts from you, Bruce.

No, I think, scouting is important here we're gonna be looking at some defoliation fully eating insects.

Later on corn wrote rooms if you're in on the corn side.

Corn room. rooms are are still the issue skeleton was, feels, and and know what you're what you're dealing with, as far as resistance and populations for next year.

Alright. Well, thank you, Bruce and Tom. Thank you as well.

Appreciate both of you participating in everybody who joined us today.

And again, just a reminder we do have a short very short 4 question survey that we'll have again as you leave this session, and part of that is just seeing what you'd like to talk about next week we have just

2 weeks left of the strategic farming field notes. program.

So on the seventeenth I believe we'll be looking at Palmer.

Amaranth is one of the topics, and then the last session on the 20 fourth, likely hitting on corn, Silas and forge topics and other issues as well.

But do you wanna put in a quick. We have a couple of field days coming up.

We got the cover prop field date, August the eighteenth of the Southwest Research and Outreach Center, by Lambertton.

Checking starts at 8 30. The program will go from 9 to one, and then the Pest management Field day that's August 30.

First at the Southwest research and outreach center in London. that's 8, 30 to 1230 versus, I think, at the time.

Right on that. No good to see all kinds of death and destruction. There you go. So yeah, Thanks for sponsors. today.

The Minnesota, slaving Research and Promotion Council and the Minnesota.

When Pests Bite Back
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