Black Cutworm and Other Early Season Pest Management

May 31, 2019. Bruce Potter discusses the current year black cutworm monitoring.

Show Notes

Episode 7: Black Cutworm and Other Early Season Pest Management

What is UMN Extension Field Crop IPM Podcasts?

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

Bill Hutchison: 00:03

Well, good afternoon. My name is Bill Hutchison. I'm with the University of Minnesota Extension IPM program that's integrated pest management at the University of Minnesota where our goal really every year is to develop and implement new IPM programs for farmers throughout the state, especially. Today, we're gonna be talking primarily about field crops and primarily about corn, at least for those who've been able to get some corn planted. Today's our first podcast on 05/30/2019, that we're following up with what was a successful run last year.

Bill Hutchison: 00:39

And we have some special guests with us today, Bruce Potter, who's also with Extension located at Lamberton, Minnesota at the Research and Outreach Center there. And we have Dave Nicolai, Extension educator, who many of you are familiar with, with his work with Extension over several years now, especially working in field crops. Today, our focus really early on this year is where we're at with a couple of key insect pests of corn, And Bruce has a lot of experience with the early developments this year. So Bruce, as we've talked about already today, black cutworm has been active in Southern Minnesota.

Bruce Potter: 01:19

You wanna just give us an update? Sure, Bill. It's been a pretty impressive year for black clutchworm flights coming into Minnesota. Basically since the April 22, we've been every week we've been getting at least in parts of Minnesota significant flight in. We're talking about eight or more moths in a pheromone trap over two nights.

Bruce Potter: 01:39

That's kind of a warning signal that there's enough moths in the area that potentially enough egg laying and enough larvae could cause some crop damage to corn. These insects also attack other crops. Sugar beets is another pest that is a concern. Soybeans, just a wide range of crops. The other thing that's happened this year is most people are aware of real late planting season.

Bruce Potter: 02:02

And what happens is we get a lot of cutworms coming in, large cutworms, and then we've got small corn and the damage can be a little bit more severe.

Bill Hutchison: 02:12

And again this year you're coordinating a fairly extensive trapping network for black cutworm. How many counties or how much of Southern Minnesota do you have covered? We've got most of the

Bruce Potter: 02:22

counties in Southern Minnesota with at least one trap. It's a pretty extensive network, and we've got a lot of good cooperators. These are all volunteers that check traps once a day, report those data in once a week. And then at my office we collate the data and develop maps and start calculating degree days, predicting when egg hatch is going to happen, and cutting will begin.

Bill Hutchison: 02:45

It's been a few days since I looked at some of your maps this year. Where are some of the hot spots or what you call these red counties so far? Well, we've had

Bruce Potter: 02:55

some real impressive flights. We've had a couple into Southeast Minnesota and also into Southwest Minnesota, West Central Minnesota. Basically, there's enough moths coming in over the spring here that most of the Southern Minnesota is at some risk for damaging populations. But the numbers have been really huge. We've been catching atypical numbers, probably over 20 per night in some

Bill Hutchison: 03:17

of these traps, and that's pretty rare for Minnesota. Right, that is significant. And where are we at, you know, with the delayed planting for our crops? That's one issue, but then of course some of our wheat species are doing just fine out there taking off the spring. What are some of the key weed species to look at for black cutworm or that might be attractive to black cutworm moths coming in and then having a large egg lay event?

Bruce Potter: 03:43

Well sure, when those moths come in they're looking to mate and then the females are looking for good areas for laying eggs. The things they're looking for are a lot of times winter annuals, some of the early season spring weeds, lamb's quarters is a really good spot for them to lay eggs in. Soybean residue is a kind of a trigger. We tend to see more problems after soybean residue than anything else. So one of the key things that people can look at is when that field was worked in the spring, when they got those weeds out of there.

Bruce Potter: 04:13

And once that happens, those fields aren't as attractive for cutworm moths to lay eggs in anymore.

Bill Hutchison: 04:19

And just a quick advertisement here in the middle of our podcast today. What's the name of your newsletter or your website that people can go to to get more information on the current updates with these cutworm moths? Well, we've got

Bruce Potter: 04:33

a series of basically weekly during the spring here as these flights were coming in. We're done trapping for the season, but we've got a report called University of Minnesota Black Cutworm Pheromone Trapping Cooperative Network, and it's a newsletter that's on the internet.

Bill Hutchison: 04:48

Google search on your IPM newsletter, is that

Bruce Potter: 04:51

gonna Well that's a different newsletter, Bill. I write way too much, and I can't see anymore. I'm gonna have to have If my eyes you go to the Southwest Research and Outreach Center website and look at for pest management, there's the There's Black Cutworm a lot of information on different flights. There's also management techniques on there. And I also put out a newsletter kind of intermittently during the summer as pest problems develop, and that's the Southwest Minnesota IPM stuff.

Bruce Potter: 05:19

That's been going as long as I've been working at Lamberton,

Bill Hutchison: 05:22

20 has twenty. Been about one hundred years.

Bruce Potter: 05:24

It feels like it. It's feeling even longer today right now, but that's been twenty two twenty

Bill Hutchison: 05:30

two years, very good. So we've talked about these moths coming in, what they can lay eggs on, and when they might be moving to corn, but that's really the next key question for corn that is planted. By the way, understand that we're about 65% of the acres, corn acres have been planted as of this past week. So we've got corn that hopefully is germinating, is going to be making progress here fairly soon, that could be attractive. Then we've got corn that's still still to be planted.

Bill Hutchison: 06:01

So in that context, where we at in terms

Bruce Potter: 06:04

of what the the so called cutting dates are? Well, good news is that just because we're getting these big flights in and we're catching these moths in the traps, we can make predictions, but there's a lot of biology and environmental interactions that have to happen. So there's no guarantee that we're going to have a lot of cutworm problems, but really people should be paying attention. We've been running this network for several years and this is by far the most moss we've been picking up for. Basically corn planting didn't get started anywheres in Minnesota till mid April.

Bruce Potter: 06:38

And there was very little corn planted when these first flights came in. Our biggest wave was on April 22. So all those fields hadn't been worked in there attractive. As the season progressed in some areas, guys got basically done with some of these fields a couple weeks ago. And then we've got other areas that nothing's been done yet.

Bruce Potter: 06:56

So, like I said, that's one of the things to look at is when those fields were worked, when they were less risk, and when those cutworms came in. Those earlier flights right now are probably going to be starting to they have to be large enough to cut a corn plant. That'll probably start happening sometime next week.

Bill Hutchison: 07:14

And we should point out that these forecasts are simply a prediction, best estimates based on the degree day models that have been validated in the past, but the bottom line is growers and consultants need to be out there watching these fields early to make sure there's no significant stand loss.

Bruce Potter: 07:30

Right, and I think we're going to have some issues with some of these wetter areas where guys went in and planted and the fields weren't in the best condition. And we're going to have some stand issues and that's going to make the scouting for cutworms a little bit more difficult because if you're seeing a missing corn plant or some corn plant that's kind of wilted, you got to determine is it actually an insect or is it just that it's had a hard time pushing through a cloud the size of a Volkswagen?

Bill Hutchison: 07:55

So nearly all the corn is still seed treated with various insecticides. So is the seed treatment gonna take care of the cutworm problem? Do I need to worry about it?

Bruce Potter: 08:08

It'll help, there's some effectiveness. The issue is though that they only last a certain amount of time in that corn plant and those cutworms could be feeding on weed species out there and then moving over to corn when they're larger. If they do that, you know, if it's a large cutworm, one bite basically, and they're gonna knock a corn plant off. You can overwhelm this by large, by a lot of large cutworms coming into small corn later on. The other thing with this timing on this is just because a plant's cut off doesn't mean it's gonna die.

Bruce Potter: 08:43

So, what we have to worry about is where that cutting's taking place and if that cutting's taking place above the growing point, the corn's gonna push new leaves out, it'll be fine. If that cutting's below the growing point, then you've got a dead plant. And that's kind of why some of these broad leaf crops like sugar beets or even soybeans to a certain extent are more at risk because that growing point's always above the ground and those cutworms are going to have a tendency to cut below that.

Bill Hutchison: 09:09

Right, and so now I'm thinking about the many we have several species of cutworms that do overwinter in Minnesota just fine, and they're going to be coming out this time of year. Some of those overwinter is late instar larvae, right? So they're coming out as a one inch size worm and they can do a lot

Bruce Potter: 09:27

of damage as well. And dingy cutworm included? Dingy cutworms is probably one of our more common species. The good news about dingies is, particularly in the case of corn, is they're one of the climbing cutworms and they tend to feed higher up on that plant soil level or higher.

Speaker 3: 09:44

Know, they're

Bruce Potter: 09:44

not gonna be in that growing point. But that's important because if you find cutworms, it's good to try to get an identification on it. Because if it's a black cutworm, those are pretty high propensity to tunnel below ground and cut. Dingies, dingies not so much. So basically, if we're seeing dingy cutworms in a cornfield, it's not usually a big deal.

Bruce Potter: 10:09

Looks ugly till it grows some new leaves.

Bill Hutchison: 10:11

Right, and so another key point for scouting purposes, especially black cutworms, aren't they more active in the evening or at night? And you might walk a field during the day and everything looks fine. How do we deal with that?

Bruce Potter: 10:27

Most cutworms are nocturnal and during the day they're hiding under bits of debris, under little soil clods, crop residue. So, you find cut plants, those are the areas you're going to want to look at, at a missing corn plant or an injured corn plant. Look at right below the surface, they tend to hang out at that border between dry soil and wet soil. So, this year they're probably about four feet up in the air in some fields. But the issue is finding damaged plants, finding cutworms, making sure they're there.

Bruce Potter: 10:58

And if you see damaged plants and you're worried, you can always flag some plants, come back a day later and see what the if that damage is continuing.

Bill Hutchison: 11:07

Okay. Very good. I hate to be the bearer of bad news, but just one more insect that I wanna ask about for this early season. Window here is, the true armyworm moth, which is another species that that I understand can migrate up here, has been causing more problems in recent years. Where are we

Bruce Potter: 11:26

at with that? Well, it's another migratory pest. It comes out of a little different area in the South. Those populations depend on what kind of survival, how far north those army worms can winter on, and what the kind of food they have during the off season in the South. But they're going to come up on weather systems just like black cutworms.

Bruce Potter: 11:46

These are attracted to a little different situation. Primarily grass feeders. They'll take soybeans, but it's last resort. They feed on grasses, so they're looking for the densest grass they can find. So winter grains, for example, are an issue.

Bruce Potter: 12:02

Fields where they have large grass along the edge and because of the moisture, we've got some of that going this year. They feed on grasses, so crops like corn can be affected. Small grains, armyworms are a big deal in small The other thing with this, we've had issues where guys have planted corn into a winter rye cover crop. Those need to be watched really close. It's kind of a bad recipe.

Bill Hutchison: 12:26

Right, right. Pros and cons of cover crops, which we'll get into on another date this year, hopefully. Right now, I just quickly wanted to go to Dave Nicolai to see if Dave had a follow-up question.

Speaker 3: 12:39

Well, think it leads into some of the things that we're gonna talk about later, Bill, that is in terms of weed control and we think about grass and so forth. No, I think you've covered it pretty well, Bill, in terms of that, in addition to that, unless Bruce has any other insect situations in terms of scouting early season corn now as it's emerging, guess we could segue into that. What are some things, and if farmers are out looking at this corn that's just emerging from an insect and or other situation or IPM or disease situation should they be looking at?

Bruce Potter: 13:16

Well, think in corn, we talked about the cover crops and I'll step in Dave's area there, the weeds a little bit. But one of the things you gotta be real cognizant on, on cutworms, armyworms, and then we've got some other pests that are a little more rare and they tend to be edge pests. Things like common stock bore. If you've got a weedy field and you take those weeds out, you're taking a food supply away from those larvae and you may not notice there's a problem until that other food supply is gone and you'll force those cutworms into your crop. So if you have that situation, it's important to look at that.

Bruce Potter: 13:57

Other things I'm kind of concerned about if this weather stays cool and wet. We had ideal conditions. These aren't insects at all, but ideal conditions for a slug mating and reproduction last fall. We can get some issues with in no till crops with slugs and particularly in soybeans. Following up with some of Bruce Potter's comments on pest management, now we want

Bill Hutchison: 14:22

to transition a little bit to where we're at with weed, especially with the spring weather, flooding, wet weather we've had and delayed planting. So again, Dave Nicolai is with us, Extension educator based out of Farmington, Minnesota. Dave, what are you seeing right now? And also asking this question in the context of both corn and soybeans?

Speaker 3: 14:44

Well, fortunately right now, Bill, what we're seeing today is sunshine as we do this podcast, which we've been really missing up until this point. And I think the biggest aspect when we talk about early season wheat growth in Minnesota, at least at this point, has been maybe the lack of what I would call for a better term, growing degree days. If we think about it from a corn production standpoint, you know, I know listening to some comments from Tom Oversted, and I know Bruce has mentioned this before also at Lamberton and both at Waseca, we're behind where we normally are significantly in terms of growing degree day units. And so we had cold temperatures in the evening, warmer today. But bottom line, it's been cooler than normal in terms of the spring.

Speaker 3: 15:27

And that also has impacted a lot of this early season weed growth. We've had plenty of moisture, but now as we kind of turn the calendar into June 1 and get closer into that, we're starting to warm up, have warmer nights, and and we're gonna see more flushes of weeds. We already have them out there, but we're it's it's really gonna come on quite a bit more. Usually, in in this time of the year, giant ragweed is the the first big emerger from a broadleaf standpoint. I mean, lambsquarters is always there right right along with it.

Speaker 3: 15:57

The waterhemp is starting to come on now, but that typically will come on even a little bit heavier as we get into the into the rest of the rest of the year. And of course, it makes a difference, what part of the state that you're in. Northwestern Minnesota has had a very good, spring. They've had a lot of, crops that have been planted early or on time. They've even been a little bit on the dry side.

Speaker 3: 16:19

So, they've had to contend with some of that weed growth before others. But with this cooler and wetter than normal spring, a lot of farmers put their first priority bill on planting, getting that crop in. So we've often talked about the need for pre emergent herbicide, not only on corn, but really on soybeans as well, particularly because of waterhemp. So then it becomes a situation with, oh my goodness, I didn't get my prion and now the weeds are coming up, what can I do? And that's where you really have to talk to your supplier, talk to your crop consultant, read the label.

Speaker 3: 16:56

You know, there's an idea there too. In terms of can this product that's a pre be applied over the top of an emerged crop and will you get, you know, control there yet? It may not control the weeds that are already up, but at least you've got it on there for future situations. So that'll be the biggest challenge. And I know that Bruce has alluded to the the the lambs quarters, you know, and situations of the complex with certain insects back and forth that are problematic as well.

Speaker 3: 17:22

So we're gonna have a lot of that. And I would expect quite a bit more foxtail with that. We've got some of our bigger seeded broadleaves that can come from farther down in the soil. Now they're gonna finally emerge, and then you have a lot of the smaller seeded stuff up that's up on top.

Bill Hutchison: 17:39

Okay, very good. Two quick questions issues that have risen the last few years in Minnesota, as well as the Midwest, is resistance and Palmer Amaranth update. But any key weed species that expressed resistance at higher levels last year, what are we looking at

Speaker 3: 17:56

In terms of resistance, I mean, we've got the ever present waterhemp and we not only have concerns about it with glyphosate, but some of the other modes of actions, what I call the PPO herbicides products like Cobra, etcetera, where we're not getting control. So in some states, it's as much as a six pack bill. If you think about it, it's a, and you can relate to that.

Bill Hutchison: 18:18

I can relate to that. Yeah, I

Speaker 3: 18:19

can relate to that. It's like a six way mode of action resistance package that can affect that. So it's there, we have to deal with it and that's why we have a two pre's situation once at the beginning, one another one over the top and maybe post because of that. So we'll have to deal with that. It's the bottom line is switch up these modes of actions and these sites of actions and not be persistent with the same one again and again in a rotation and scout.

Speaker 3: 18:45

Palmer amaranth, just real briefly on that. It's not everywhere in the state of Minnesota. Have picked it up in pollinator situations, and you can talk a little bit about that on maybe on another show. But we are concerned about that. But this last year, in other places, and now towards Bruce's area, down in that particular area with Redwood County.

Speaker 3: 19:04

We had some situations where we had screenings from feed that went into the with cattle feeding, went into the manure and ended up with some spot infestations of palmer amaranth. So there's different ways it can come into the state of Minnesota. We've maybe had a half a dozen counties so far. But the bottom line is, you know, as we get farther along here, look at something that in your field, it's getting big, if it has long petioles on it, that's apart from the blade of the leaf back to the stem. You know, situation with that, you know, in situations that it could be Palmer on the edge of the field, but get some expertise, get somebody a second, third opinion, and let the Minnesota Department of Ag know.

Speaker 3: 19:44

Right. Some of the population is resistant to glyphosate, some of it is not, but we're gonna basically treat it like

Bill Hutchison: 19:50

I it think a lot of people will be looking for it And carefully this then

Speaker 3: 19:54

let the Department of Ag know, our bottom line is it's primary noxious weed and we wanna eradicate it.

Bill Hutchison: 20:00

Right, very good. Well, wraps up our show for today, and we look forward to hearing from many of you, talking to many of you in the future podcast as we go forward this summer. So thanks again, Dave and Bruce, for joining us today.