Getting ready for late-season insects
Dr. Robert Koch, U of M Soybean Extension Entomologist, and Bruce Potter, U of M Extension IPM Specialist discuss soybean and corn insects to keep an eye out for as we move into August. Soybean aphid populations have overall been low this year, but there are pockets of increasing population. Scouting is vital to determine where issues may be or if treatments aren’t needed. Other insects discussed include soybean gall midge, spider mites, and corn rootworm.
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Extension. This is strategic farming field notes. today's topic will be on soybean and corn insects, action, thresholds and status and the big question are we done for the year these sessions.
Are brought to you by the University of Minnesota.
Extension and dinner support from the Minnesota Soybean Researcher and Promotion Council along with the Corn Growers Research and Promotion Council I'm Dave Nicolai along with Anthony Hanson
the retail extension educators in crops. We are serving as moderators.
This morning we welcome our panelists this morning Bruce Potter integrated test management. specialists from the University of Minnesota, located at the Southwest Research and Outreach Center at Lambertton, Minnesota, and also
Dr. Bob Cook, whose extension Soybean, animologist from the University of Minnesota.
So with that I'm going to turn it over to my co-host integrated Pess management specialty, Anthony Hansen coming into us from Western Minnesota.
Someplace out there in that Morris area. So Anthony did get a little bit of rain over the weekend or this past week or not.
Yeah, Dave: actually, so Bruton area here can Alexandria moving area.
We got about 2 inches of rain just yesterday. but kind of a narrow band.
So we got really lucky where we are many other dry areas in the region, too.
So pretty variable depending on how that ranger knows for people.
Well, that's certainly the case I I know that just mentioned some places in in Southwestern Minnesota didn't get the rain, and certainly I'm in Eastern Minnesota more towards the Metro area
here in in Dakota county, and we've been missed consistently throughout the summer.
Here, so we're we're way behind average so bottom line a lot of variability.
I I guess so, you know, with that and here to help us with some of this variability.
Bob, a little bit on from your standpoint, everybody, and keeps asking me, where are the soybean methods?
Yeah, thanks, Dave. you know. First off, I guess you mentioned, you know.
Are we done with insects for the year and i'd say certainly not in Soybean.
I think we're just getting to the point where things could start getting interesting, and if an entomologist is saying that I can ask, they always used to say, You know, you might want to be concerned.
The Soybean athens they're definitely out there I think this variability in weather and plant growth stages is leading to variability across the State in aid populations.
There are some areas where, if the numbers are increasing, Southeast, Minnesota, Central, Minnesota.
Got a report yesterday. and it was kind of from Clara City up to maybe Sox Center.
And then I think, Bruce, You've been seeing it if it's increasing in Southwest Minnesota.
But you know a lot of this will depend on weather, I think, for Aids and spider mites, you know, over the next couple of weeks.
Kind of determine what are what our main issues will be? Yeah, Bruce, what are you seeing in Southwestern Minnesota in terms of So I mean, if it out there I know like if Bob Mansion where
i'm in Central minnesota west Central really variable. my cases I've already seen this, so we've been getting up this year, whereas we go Look for the South through East and hi Bob mentioned.
There are a few pockets for people are finding if it's Well, I think it's the same here.
It's real variable if you get in these areas that traditionally have some a foot populations early we're we're seeing some buildup I think there's probably a few fields that have some
recommendations put out on them, yet. but they're pretty scattered.
They're the small fields feels with a lot of buckthorn around him at the research and outreach center.
We've got a serious setup for insecticide trials.
We've been watching that, and as of yesterday that's now, a 100% of the plants have aphants.
Those populations are are still fairly low averaging about 15 per plant. but you know, when i'm looking at a feel, for if it's my first queue is as those flip percent plants infested go up once you
start getting over 50%, and certainly when you're in 100%.
You really got to start paying attention because there's no place else for them to go. There's no new plans to colonize, and those populations could build up pretty rapidly.
So we're just have to wait and see we don't have any rain here at Lambertton, and that's gonna maybe encourage some of those populations to leave if we get the beans under moisture stress open some
things up for spider mites as bob was saying I was going to say next week is farmfest, Bruce, of course, and and of course, always time with firefighters. It's going to get warmer and it looks like It is next week, you know
we're talking eighties into the into the ninetys what do both of you think about the temperature effect Not only on on saving? if it's do we have to be concerned about spider mites at some point or are we still too far away from
that in a in a dry situation. I think for soviets I mean there's research out there that was done in a girl chamber that showed that the aids don't perform well under higher temperatures you know up into
the you know, mid nineties and higher. but you gotta remember that that work was done under constant temperatures 24 h a day at those high temperatures.
And in a swiping field you got the canopy of the beans mitigating that temperature a little bit.
You've got that fluctuation from day to night, we where, even though you're high temperatures in the day, might be in kind of a stressful zone for the aphids you know the other part of the day
might be closer to the sweet spot where they can still be reproducing.
So, just because we run into a stretch of hot weather do not count the if it's out.
No, that was kind of a follow-up was thinking about, too, especially considered what whether we might be have going forward.
You know, in some of these fields were people barely seen an atheist.
You might have just a couple on the top leaves right now.
Is there no still definitely a potential for issues to pop girls fields Well, we can't bank too much on predicting what's gonna happen quite yet.
Based on current accounts. Yeah, I think they're still concerned you know these athletes, our very mobile.
They developed that wing form, and they can fly around to different fields.
Could get a call in any event like that happening and previously uninvested fields could get colonized, and if there aren't many natural enemies there, or anything and if temperatures get into that sweet spot for the
eighth, and their numbers can increase very fast see bruce What are some tips for if you're gonna if a grower or or a professional is gonna go out scouting these warmer temperatures where in the canopy, should they start to
look for from if it's to get a better assessment going forward and think of natural enemies, etc.
Well, I think I think those if they're gonna be wanting to be on that new growth.
Yet as long as those plants are growing vegetatively they can move to the under side of the leaves to get protected, and that's usually where you find him.
Anyhow. But the other thing that's gonna happen is as these plants start grow reducing vegetative growth, and and you get the later the reproductive stages you're gonna start to see those 8 if
it's Move further down in the canopy you'll see more on the stems. you'll see a more around the pods, and then real late as those plans get back and get to get into 8 the
r 6 stage for that full pod stage then you'll start to see them more towards the bottom of the plant.
So right now it's probably as these beans are in our 3. you're probably it's probably pretty easy scouting.
A lot of those are going to be at the top of the plant. but they're going to start moving down in that canopy as a season progresses.
Any comments on action, thresholds and and product choice or things to think about here for either one of you.
Well, I think again, just to reiterate with all this variability across the State. we wanna make sure we are scouting and not just assume we've got issues of getting in the field estimating numbers of if it's.
On plants. we still recommend the 250 if it's per plant as a threshold.
Then The majority of the plants invested and I deal with that population increasing, and to know if the population's increasing, we need to be scouting over time.
As for management options or insecticide options, remember that core pause, you know, so think of things like Laura's band.
What's the fairly common mixture Cobalt? I think no longer use those due to that epa action where they revoke the tolerances.
So if you have leftover stock of those chemicals remember you can't use those but we do have other products.
Well before getting into those and there's also resistance to the paritroids in many soybeanate the populations.
So we've documented over several years now resistance to by fan thread and lambda is a health right, and we suspect that they're could very likely to cross resistance to some of the other
pyrethroids. So you know, with with those 2 items, the regulation and the resistance it's really already reducing the size of our chemical toolbox for this past.
But we do have some newer products like transform, Sophie, you know, and Sabanto.
Our research suggests. that they're effective against david's and they have the added benefit of being a little bus toxic to some of the natural enemy.
So you can ideally kill off the aids and leave the Lady Beatles and other predatory insects out in that field.
And then there are still some of the mixtures.
To that. at least my data has been suggesting are still pretty effective.
Bruce i'm curious to hear from you but you know some of the mixtures where it's a pythroid and new and nicotonoid.
Those still seem to be holding up for the most part
So here's a question thinking about no people are going out replying some of these chemistries work a little differently.
Either Bob or Bruce. what are you looking at for? Fcc. afterwards?
I know One of these can definitely have different effects on the Athens, where you might not.
What looks like, you know, Dennis right away at least that Yeah, that'll be sophisticated.
The feeding stops right away, but they hang on for a few days while, or starving to death.
So if you like torturing aphants that's a product you might want to select but there's a you know.
So there's we've got a pretty good range of options for soybean, if it's right now.
Even if, in spite of the lack of wars, man and clarify us being gone, I think one of the concerns is, you know, people will need to be proactive and and look at insecticide availability just
like everything else. Some of these products are in short, supply in different areas.
So you know you don't wanna be caught unaware The other thing that's gonna happen right now is is we're moving into that period as this vegetative growth stops we're gonna see a lot of
dispersal of infants. they tend to move around round farmfest time. storage motorcycle rally. That's kind of the queue, for when we see a lot of that move but between.
Feels happening, and I know there's some people that have tried to get away with the the cheap and easy way, and have mixed it insecticide, and with their fungicide, or their herbicide and those are
the fields that people better keep an eye on because depending on what product they've used.
They may have used a product that the if and sars are no longer susceptible to, and they may have knocked out all the beneficials in those fields.
So it's some those fields are the ones that that need a special.
They're gonna need a special watch you know later on the season unless you're up fishing and don't care.
And then it doesn't matter, Maybe we should move on to talk a little bit about some other soybean insects.
Including galm age or good Bruce.
But maybe Bob you had a curious sample I know we talked about a little bit earlier. But there are a lot of things that can happen out in that soybean field i'm just even beyond if it's at this
point time. Yeah. So last year we documented for the first time a tiny leaf mining moth whose caterpillar minds and the leaves of a couple of native plants, and last year we found it feeding on
Soybean A colleague of mine also found it in Quebec.
I was kind of hopeful that it was just gonna be some kind of a novelty thing where we'd maybe see it here and there.
Never add any damaging bubbles. but I went out and visited a field earlier this week in Sydney County, so kind of near the Minnesota River, and it was hit pretty hard. You know, especially along the edge of that field near
what in areas a pretty fairly high percentage of the leaf area was affected by these.
We know very little about it, you know. It was just feeding on these 2 kind of obscure native plants previously, so nobody has ever studied it all that much.
Last year was the first time we saw it on Soybean.
We're kind of like swimming go image we're playing catch up here trying to figure out you know about his biology.
It's past potential things like that. but I think with this one you know as it's mining in the leaves.
It leaves a kind of white paper, your list your like mine on the underside of the leaf, and then, as the larvae get bigger, they start feeding on more and more.
The leaf tissue, and that leave tissue eventually dies out.
So I I think we'll end up managing it as you know, estimating defolation or percent a leaf area affected like we do some of the defoliating insects in this particular field the to the
field was, had a very low, level infestation, but there was at least one edge that was yet pretty hard.
So in the lookout, for we did post a crap news article a couple of weeks ago about it. but i'll have some pictures.
Okay, Thank you. But all the time here for both Bruce and Anthony your Western areas.
Can you give us a quick update on gomage in soybeans?
Bruce, you're engaged in a significant you know regional monitoring situation, kind of where where are we at now?
At this point in time in the year. well we've got right now we've got this the first generation of flies being produced on soybeans that the overwintering generation that came off the last year's soy being
grown into this year. so I mean that for the most part those populations have been fairly low.
There's some edge infestations but we compared to some of these higher years.
2,000 20,020 the the the crop injury is not nearly as severe as it has been.
That may change because we're catching an awful lot of adults.
Now we'll have to see what happens one thing we've learned, is it doesn't seem that you know the the dry, hot, dry weather keeps the adults from from emerging so as as these eggs are laid and
larvae emerge it's gonna be easier to find. go image and fasted field, so as people are out looking look on those edges of Jason to last your soybeans and look for for the crop
injury we're seeing a lot of soybean rut diseases that's causing wilting and some hail sand blasting injury that's causing some brittle stems so make
sure you're peeling that outer layer that stem back and finding larvae before you.
You blame it on salt on go image when it's actually a another problem.
So what would be the crop? injury, symptoms?
And Anthony, have you seen anything? Yeah, a little bit farther north here or not?
Yeah, it was kind of on the northern end or Bruce.
I think you said a candy I county Last year you had a find out there with decent infestation out there.
So far this year. I haven't seen anything until I went down to Southwestern Minnesota to see some of Bruce's sites down there so so so far, quite up here, but still early in this season like
you mentioned, too. So Bruce is that how about you Well, it's It's pretty.
We can find them. but it's not it's you know usually right now in July.
You know the first part of august is when We're have the most success of picking up new fields.
We'll be heading east and and north trying to look at some new counties as well, so we'll see what happens.
It's hopefully. these populations in minnesota stay fairly low.
The first thing you're gonna see a debilitated plant. if from the edge of the road in terms of driving down what's your first sign?
You know if you some of these invested plants if they're invested early. They're stunned and they're beneath the canopy, so they're wilted and brittle, but they're underneath
the canopy, so you don't notice some many more of this surrounding plants have have have covered them up.
But if you look at what you're gonna start to see now is always at the base of that plant, you may have to to actually look for Is that this coloration right near the ground level and usually towards the at the edge of
that affected area. There'll be a real dark almost black border between the green tissue and the healthy tissue.
Look at those plants sometimes they're brittle not always if the infestation is pretty light sometimes they're wilted.
But again that's when those number of larvae perspective get up, but always peel that that outer layer back and and see if there's larvae underneath it.
We've been listing a couple of urls on the back and your screen in terms of previous publications.
But maybe just Bruce, and bob are there or you know. you mentioned, maybe just review what are some plans for crop news for some upcoming articles that'll be timely Yeah, So Bruce, and I are working on one recapping So
i'd be naked and spider mike scouting thresholds and insecticide, or might aside options i'm working with teresa Cyro from the Mda to put one
together on corpse and reminding folks that we shouldn't use it even if we have leftover product.
And hopefully, some updates from the Mda on disposal.
So we got a couple of questions coming in here i'll i'll put them together in this case.
Are we seeing anything for either grasshoppers or thisal categories this year?
Grasshoppers. Yes, this little caterpillar is not so much, at least not in in my areas.
The stuff I've looked at. Okay, you know like the the almost all the grasshoppers that i've seen in Southwest Minnesota are red legged, and so they're gonna Hang you know particularly
around alpha fields. they're they like to have it lay eggs in that in that alpha ground.
There's some differentials as well but those are the 2 main species, in general, are really low I haven't seen much green clover.
We're mute yeah you mentioned that Bob I haven't pretty much either.
Right perspective kind of strikes county area a lot I felt out there. That's where i'm seeing most of the grasshoppers, too, and get into the savings to see a little bit of feeding
damage sometimes, but yeah, nothing that's anywhere near threshold or not. Very high numbers out there.
Deeply out for things like Pod. The thing if you do get later in the season, and you get high numbers out there.
But that remains to be seen if we get to that point.
For so even at least any other soybean insect concerns, before we kind of jump over to corn here a little bit I think the last one to cover is spider mice a what we might be expecting if we
get to another hot, dry August like we tend to get what happening there
You know, I think the situation's kind of prime for spider mites in some areas you know with the the dry weather.
The spider mites like the heat and and the dry weather.
You know, Bruce last week was chatting with me about it, and, you know, made some comments about you know maybe spider-ite numbers going into this year might have been a little bit lower last year because of some disease
outbreaks knocking the my populations down but they can reproduce quite rapidly.
So it's it's another thing to keep an eye on especially in areas that stay hot and dry.
Have a note here from our meteorologist to the south.
Here, Dennis Taylor, out of Usda and on Ames.
This is hot and dry, I guess, coming in here to in terms of
Predictions in August, especially hot. seems quite likely.
I know the Pacific Northwest forecast this morning was for extremely hot temperatures out there and triple digits.
So with that, just as we talk about spider mites and Bruce, you've talked about this before. What you know.
Kind of scouting is difficult, but pulling the triggering economically is even more so.
Isn't it. Well actually Spider, might scouting is relatively initial stages are relatively simple, because, you're probably not gonna wanna treat any field unless you can actually see some sort of damage on the edge of the
field. what you're trying to do with spider mites is protect the upper canopy.
So you're gonna see some areas on the edge of the field with particularly with some stippling.
Yeah, and and you know some small colies on the upper leaves.
But you don't want to get to the point where starting to lose that love for proper leaf area, because it's not replaceable.
Sometimes guys, especially in these bigger fields, can get by with an edge treatment.
But you really have to scout hard and make sure you don't have infestation pockets further out in the field.
Because otherwise you they, you know, the the center of the field just blows up, and then the edges get reinfested as well.
So kind of last word are there some insecticides, though to stay away from in a spider might situation here for both Bob and Bruce except by Katherine and stay away from the
corporeal cost that might be sitting on your shell.
How about the mitochondria There are a few other options we have for ?
Lighter rights that we don't have for say Soybean? but most of the others are pretty similar.
But how well do those work or What kind Yeah, when or kind of what life stages their targeting.
Bruce, do you wanna take that? I think you've got more experience, maybe with those might asides I I actually haven't yeah.
So So some of these like by phantom for example doesn't control eggs.
So you're taking out the amateurs and the adults.
And and you know if you're if you don't have enough residual There, you can have a catch and get reinfested.
Some of the products, like zeal work primarily on eggs in the very small images.
Those have some tho those struggle if you're trying to put them on a full blown infestation.
Because you've still got the adults the adults are still laying eggs.
That sort of thing. the products we've got our dimethylate yet. particularly if you're just going after Matt Mike's di methylate agrar mac by fatherine but you gotta keep the rate
up. That's the other thing there's some premixes with Bifanthron in them that have mites on the label.
But you got to be really careful of what rate of bifanthan you've got in there because well, I don't have a reduced rate, you know.
You might be on the edge for might control. maybe we should jump over to corn a little bit, Bruce.
Here and we're in the end of July comments about how Rome is looking from the standpoint, and then also sticky traps digging ruts, etc.
What are some things that you could they want to mention here for our participants, you know, over the next few weeks It's time to scout beles. if you've got an early silking field right now, you might wanna especially if
you're in area with a lot of northern things like sweet corn or real early.
That's a problem. But we're into that time now we're making decisions for next year's corn crop.
So if you're we've got quite a few cooperators and you sticky trap program.
But if you're running, sticky traps or even doing doing whole beetle counts on plants.
The time to do it you don't want to go out there too early, and make too many decisions or early because they're males.
What we really care about is the females that are laying eggs.
We've got pretty good population as the winner didn't do very much to the Western legs.
Unfortunately pretty significant damage at Lambertton again. and i'm getting some reports of feel struggling.
They may look fine right now, at least as long as there's enough moisture.
If you don't have the wind but we've got some plants that look pretty good in our research bots at Lambertton that you can pull out of the ground pretty easily with one hand.
So and this we, as we get short on rain now that's going to get worse.
So basically, start scouting for beatles and and the other thing Right now we are picking up some Western being cut room in the light traps, which is pretty unusual for us, not big numbers.
But if you're out there, maybe kind of look at the upper leaf surface of some of these corn plants, and and see if you can see some eggs University of Nebraska, probably got the best extension.
information on on that insect If you're going to be looking at corn you would spend some time on obviously corn on corn, or any particular trait that comes to mind here as to where to put your energy oh, as far as as far
as r works scouting well I mean I mean if you're in continuous corn
There's populations of Western chord where i'm out there, and even some of nor we're starting to see some with northern's where we're resisted to multiple traits in the pyramids just
you know the non vt hybrids of course, in a continuous corner situation are at particular risk right now.
But there is We've seen a lot of issues with smart stack and chrome, and and the durricate hybrids out there as well.
It's just a matter of what level of resistance is in that local population, and what you're overall as far as what the damage is going to be.
That's really why, you're scouting dave is to find out what those beetle populations are in a particular field. and then what that means for for corn down the road you know if we're gonna get this
hot and dry. I guess, Bruce, would you, Window, always assume that everything that you see is debilitating the corn plants?
If you have a reduced root system and cornered Orman interaction if we getting these hot dry conditions as Dennis was talking about in into the month of our August.
Oh, yeah, definitely, because if you've got if you've got a reduced root system, and you're having a issue taking up moisture and nutrients for that matter But if you're having a in a period root system the effect of a certain amount of what
pruning is magnified under drug under drop stress.
So your your possibility, allele, yield loss goes up with dry weather.
Definitely. So yeah, yeah, this case you mentioned continuous corn.
Is that still the best tool we can use across the board for trying to keep our rotations going to avoid continuous corn.
If a grower can at least some lifestyle growers might not be the easiest to do. But
What effects do you still see from avoiding those involved with more at least a corn saving rotation, or
And you've already got traits that create a pure minute hybrid out there.
Really the the smart thing you're the only effective thing you can do right now is to rotate out of corn, and if you have more than a half and no have gone on a pyramid you need to report that and and technically
you're not supposed to plant corn bt back into that field.
The problem. we've got in addition to westerns right now is we're seeing Northern corn rover populations go up, and i'm looking at field this week.
That's got in in along the iowa border that's got quite a few northern corner or a minute, and and it's a it's a pyramid field so the bad news is extended to I
pause can go along with bt resistance so that the comments we talk sometimes every year a little bit about.
If there is a volunteer corn situation in soybeans here, and you alluded to extended Diapos, I mean any comments there, Bruce.
Certainly those are our suspect things as Well, Well, definitely if You've got volunteer corn out there, and you kill it late of it.
If it was still live a few weeks ago. the The rooms larvae on those rits probably could could could have survived, and, make it to adulthood.
The other thing. it happens with volunteer core now is it tends to silly later.
Now pulls beatles into that field so it's bad out there, in addition to possibility of reducing soybean deals for that volunteer corn is heavy it's got it's got some
ramifications for the orman they're not good it Certainly, if you've been planning some of the traded corn in the past, and we think about somebody's herbicides, the flops and the dims some are going to
be better than others works. work with your crop consultant or your supplier
Otherwise you'll be you know putting the product out there from a herbicidal standpoint, that isn't going to do any good.
But at this point I think we're to the point where we're gonna have to do some hand you know labor out there.
Do what you can to get the volunteer corn out of that situation, particularly from going to going to see as well.
When you get these patches and and you know relatively high populations and areas, the fields that's where you could have some issues down the road.
I think that gets us to about time here. So Bruce, said Bob, thank you for joining us today.
Takes care of all the we've got the it looks like so dated.
I'll have it off here. Yeah, Well, thank you very much. Anthony.
We wanna thank everybody for attending here today, and we thank our panelists.
Both the Bruce and Bob. we have a very short 4 question survey that you that you can participate in, and you conclude the session today.
Again. We want to thank our sponsors Minnesota.
So I mean Research and Promotion Council, along with the Minnesota Corn Research and Promotion Council and the University of Minnesota Extension.
You can tune in next week We will be on the air even though we far fast.
We'll have some other moderators and that'll be again on August third.
I believe Anthony is that correct and it'll be a Wednesday same time at 8 o'clock, and we'll have an updated crops program.
We will continue with that situation. so thank you anthony if you don't have anything else.
We'll conclude, and and again, thank our our panelists interpreting, and we have recorded this as a podcast and for future delivery, as well as a recording of the actual session itself.
So thank you again for attending I appreciate that and We're signing off from here at the University of Minnesota extension.
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