4 - 2021 South Central Ag Lab Field Day - European Corn Borer

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10/14/2021 Added

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4 - 2021 South Central Ag Lab Field Day - European Corn Borer, Ron Seymour, Nebraska Extension Educator

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[00:00:07.910]I'm Ron Seymour. I'm the
[00:00:09.590]Extension Educator
[00:00:11.200]located in Adams county with the University of Nebraska Extension.
[00:00:14.900]And today we're going to be talking about European corn borer and European corn
[00:00:19.640]borer is a pest that we have had in this country since the early part of the
[00:00:24.560]19th, 19 hundreds. And it was introduced from Europe and,
[00:00:29.450]it has been quite a problem for corn producers and vegetable
[00:00:34.400]producers for ever since it was introduced into this country. There's just not,
[00:00:39.530]parasites and other predators that help control it very well. And,
[00:00:44.600]so we had been dealing with this past for such a long time. And in,
[00:00:49.310]in the whole time we have used an extensive amount of pesticides
[00:00:54.080]insecticides to help control this past every year that we grow field corn,
[00:00:59.120]in particular.
[00:01:00.890]And that's where it's primarily a past is Forrest is in field corn,
[00:01:04.400]but in the late 1990s,
[00:01:07.550]a new technology called BT corn,
[00:01:10.640]was introduced that substantially,
[00:01:14.600]did a substantial job at, controlling this particular pest.
[00:01:18.740]And they incorporated the toxins that,
[00:01:22.640]from this soil bacteria that the plant then expresses.
[00:01:26.480]And when the larvae of the European corn borer feed on the
[00:01:31.130]plant leaves, they pick up that toxin and it'll kill them.
[00:01:34.730]And so it's very effective. We significantly have reduced the,
[00:01:39.680]the amount of insecticide that we're applying in the environment and,
[00:01:43.330]and also we've significantly reduced the population of this particular
[00:01:48.140]pest. And so it's been a really good thing for us,
[00:01:52.790]to have in today's agriculture, but,
[00:01:56.630]we still do have situations where European corn borer can be a real problem.
[00:02:01.790]And, you know,
[00:02:03.050]I have a graphic here where we're looking at European corn borer larvae.
[00:02:06.650]That's been feeding on a reproductive stage, a corn plant,
[00:02:10.970]and it's broke the top off. It's broke the,
[00:02:14.100]has significant tunneling underneath the ear.
[00:02:17.300]And the ear is actually broken up because the larvae was feeding on the
[00:02:21.650]inside of that ear shank. And that's what it does. It feeds on the ins,
[00:02:26.690]early on it'll feed on the leaf tissue,
[00:02:29.900]but then as the stems get bigger and the larvae get bigger,
[00:02:32.720]then they'll bore into the stock and they can make the stocks
[00:02:37.670]weak. And then those stocks also are not able to deliver the nutrients to the
[00:02:42.560]developing plant or to the developing ear. Now,
[00:02:45.110]European corn borer does have two generations. And so, each year.
[00:02:49.130]And so we're concerned about it both in world stage corn,
[00:02:52.910]and then in reproductive stage corn, we,
[00:02:56.240]we do see it damaging field corn, but also in,
[00:03:00.940]Whitefield corn, which we use pretty often for food,
[00:03:05.080]for food grade corn. We also see it in popcorn and in sweet corn.
[00:03:09.820]And so in addition to corn,
[00:03:12.340]it does have ranges of other plants that'll feed in such as grain,
[00:03:16.900]sorgh cotton in the Southern part of the United States, potatoes,
[00:03:21.400]wheat, peppers, apples. There's just a lot of things that'll feed on. In fact,
[00:03:26.350]vegetable growers have a real significant problem with it and potatoes and
[00:03:30.700]peppers. Now, it's important to understand how to identify this past.
[00:03:35.950]you know, we're, we're really interested in what the larvae looks like,
[00:03:38.710]and it's,
[00:03:39.220]it's a little worm that has some spots on it and kind of a pinkish color,
[00:03:43.330]but it all starts of course, with the, with the moth,
[00:03:46.570]it's a small Delta shape moth I'll, about,
[00:03:51.010]maybe a half an inch long,
[00:03:53.050]and it has a it's kind of buff colored or cream color and has some wavy lines
[00:03:57.790]across the wing. And then a first-generation.
[00:04:01.240]We usually see those emerging about,
[00:04:05.380]the middle of June. They lay eggs on world stage,
[00:04:09.820]plants,
[00:04:10.720]and those eggs are usually laid both in the vegetative
[00:04:15.760]stage of corn and the reproductive stage on the underside of the leaves,
[00:04:20.470]usually near the midrib of the leaf and the eggs,
[00:04:24.910]are a late in masses of oh 25 to 30 eggs
[00:04:29.830]and they're white and they're discharged.
[00:04:32.350]And they're arranged such that they look like fish scales in this
[00:04:37.030]mass. And then, as those larvae developed, depending on,
[00:04:41.920]the time or excuse me, it,
[00:04:44.260]depending on the weather usually take five to seven days,
[00:04:47.290]right before they hatch,
[00:04:48.490]they get a little black pinpoint that is actually the head capsule of the
[00:04:52.540]larvae. That's about to merge. Then they emerge and then the little,
[00:04:55.180]little worms will start to move upon the plant seeking
[00:04:59.530]shelter. And, in world stage corn,
[00:05:02.950]they'll move to where the yellow tissue is right down in the world.
[00:05:06.550]They'll start feeding and reproductive stage corn.
[00:05:09.010]They'll they'll feed on the pollen a little bit.
[00:05:11.080]They really like to head to the,
[00:05:13.480]the silks of the year where they'll feed. They can feed on the, on the,
[00:05:18.730]ear itself, the developing air, but then they really, in both stages,
[00:05:23.170]both generations, they will then bore into the stock and feed it in the stock.
[00:05:27.820]And then of course on, reproductive stage they'll,
[00:05:30.190]they'll bore into the ear shank and they'll make those all week.
[00:05:34.510]So during the growing season,
[00:05:36.550]the larvae will then complete their development and then they'll pupate.
[00:05:41.350]and, the second generation MAs will start to emerge,
[00:05:46.120]oh, at the end of July, first part of August. And then those larvae will,
[00:05:51.040]the, adults will lay eggs again,
[00:05:53.590]and then the larvae will hatch and then they develop usually, oh,
[00:05:58.310]tell the, end of September, mid September into September,
[00:06:02.690]and they'll, they'll go through the winter in the stocks.
[00:06:07.670]and then they,
[00:06:09.950]will finish their development in,
[00:06:12.940]in the spring and pupate in the spring then to continue the life cycle.
[00:06:19.100]All right. So these overwintering larvae are overwintering it plant residue.
[00:06:23.930]And, then, there are these two generations a year.
[00:06:28.460]You may have heard of single generation, those are New York strain.
[00:06:32.580]So in the Northeast part of the country, we see single generations. Now,
[00:06:36.350]when we see the damage on world stage plants,
[00:06:40.250]they feed on these, the leaves when they're in the world.
[00:06:44.960]And as those leaves start to come out,
[00:06:47.960]then you start to see the damage and it looks like somebody shot the plant with
[00:06:52.010]a shotgun. And we described that as shot hole feeding damage,
[00:06:56.180]and then you'll start to see them move later into the stock.
[00:07:00.740]And as I mentioned in the reproductive stages,
[00:07:03.830]they're headed right into the ear tip. And then they,
[00:07:08.090]they cause a reduction in grain production, stock, breakage,
[00:07:12.320]harvest losses. And then when they're feeding in the ears,
[00:07:17.270]they, are of course making droppings,
[00:07:20.330]we call that frass and that frass is very susceptible to rots
[00:07:25.460]and molds and the stocks get weak also from a rotting.
[00:07:30.170]And so it, not only do we get the plants that'll fall over the years,
[00:07:34.580]it'll drop off, but you, if you have these molds in the,
[00:07:39.380]in the year itself, then you can, get some discounts,
[00:07:43.550]have to be subjected to some discounts at the grain elevator.
[00:07:47.150]And when will you look at yield loss?
[00:07:49.010]There's a lot of research has been done on that, and we get more loss,
[00:07:53.630]the year for the S the longer that I,
[00:07:57.560]the larger your on the plant, we get more loss.
[00:07:59.510]So when early world stage infestations, we get five and a half,
[00:08:02.750]5.5% yield loss,
[00:08:05.600]whereas later on is 4.4. And then we get this second generation.
[00:08:10.190]If they start to infest the plant and pre tassel,
[00:08:13.910]we can have up to almost 7% yield loss and then pollen shed
[00:08:18.260]4.4 blister three. So it, the, the later it gets in the season,
[00:08:22.880]the less damage we actually see from them. Now we do monitor these,
[00:08:27.020]the flights of these MAs with, different traps.
[00:08:29.930]We have a black light trap that you can see here on your, on my right.
[00:08:33.650]And then we have these pheromones scent traps that attract just the European
[00:08:38.600]corn borer, adults to those. And you can see from this graphic, this is,
[00:08:43.520]the, typical light, flight trap.
[00:08:46.940]This was taken here in clay center in 2002.
[00:08:50.750]So the numbers are going to be a little less,
[00:08:52.700]but we still have these same patterns where we,
[00:08:55.620]this large peak in late may,
[00:08:59.190]mid or mid to late may,
[00:09:01.050]and then another peak in late July and through mid
[00:09:05.640]August. So when we scouting for these, the,
[00:09:09.390]the light trap catches will tell us when, really just start scouting for these.
[00:09:14.460]And so first-generation,
[00:09:15.570]we're going to look for these shot hole feeding damage in the
[00:09:20.100]world,
[00:09:20.970]and then we're going to record the number of live larvae per whirl.
[00:09:25.710]And then in second-generation,
[00:09:27.000]we're going to look for number of egg masses per plant,
[00:09:30.300]and usually concentrating right in that era zone, the, the ear,
[00:09:34.740]the leaf above the ear, the ear leaf, and then the leaf below, the air,
[00:09:39.720]because that's where the majority of the eggs are going to be located.
[00:09:43.470]And then we use a, a,
[00:09:45.180]some tables to do a really accurate job of trying to determine what the
[00:09:49.860]threshold is. So what we're looking at is the number of larvae per plant,
[00:09:54.060]and then what the yield loss is based on the plant growth stage.
[00:09:58.470]And then that'll give us a dollar loss based on what the value of the crop
[00:10:03.420]is.
[00:10:04.890]And then we're going to compare that to what it costs to make an application
[00:10:09.630]through whatever method and if the, the amount of damage,
[00:10:14.550]that would be caused by that level of infestation exceeds the cost of control.
[00:10:19.140]Then we recommend that some kind of control measure be initiated.
[00:10:22.800]Now it's a little different and popcorn and sweet corn,
[00:10:27.210]popcorn.
[00:10:27.810]We're looking at an economic threshold of 25% of the plants with feeding
[00:10:32.280]damage and larvae present.
[00:10:34.620]That's going to be in first-generation and then, second generation,
[00:10:39.450]we're, we're going to look at something similar to that.
[00:10:44.190]maybe a little less, about, about the same level, and then in sweetcorn,
[00:10:48.930]we're looking at 20% of the plants with feeding damage and large number of MAs
[00:10:53.520]being found in local traps and sweetcorn.
[00:10:56.520]We're going to just basically start spraying on a five to seven day schedule.
[00:11:01.290]Once we see a large number of MAs or larvae present now in
[00:11:06.120]field corn or white corn, yellow, and white corn,
[00:11:09.780]we also have a different threshold. so we're looking at the,
[00:11:13.950]the number of bagged masses,
[00:11:15.540]and we assume that we get about three corn bore larvae per egg mass.
[00:11:20.460]And so that's going to give us the number of bores per plant.
[00:11:23.310]And when we look at the yield loss, depending on what the growth stage is,
[00:11:27.540]and that'll give us our bushel loss,
[00:11:29.400]and then we look at the value of the crop and here again,
[00:11:32.340]then we're going to compare that to the cost of application.
[00:11:35.670]If the cost of application is less than what the,
[00:11:39.120]the economic loss would be,
[00:11:40.740]then we recommend that some kind of treatment be done. Now,
[00:11:43.920]there are some cultural controls that we can look at.
[00:11:46.590]Planting date is really important where we can look at later planning,
[00:11:51.330]we're going to have less first-generation, damage,
[00:11:54.970]but maybe more second-generation damage. And then we also,
[00:11:59.240]particularly in early small plants, we have some plant resistance.
[00:12:04.360]there's a chemical called Dumbala,
[00:12:06.610]that's the initials for a really long chemical name that will actually kill
[00:12:11.470]the larvae when they plants are small.
[00:12:13.930]Now the plants do tend to grow out of that,
[00:12:16.750]and then we'll see more and more damaged later on. And then,
[00:12:21.010]we do have some differences in sheath and collar strength,
[00:12:24.370]depending on upon the variety. And then one thing that's really important.
[00:12:27.910]And we see this a lot.
[00:12:28.930]I mentioned this earlier is we do have these BT corn hybrids,
[00:12:33.040]and as long as we're using multiple traits,
[00:12:35.890]we are getting really good control. Still.
[00:12:38.830]There was a location in Nova Scotia, Canada,
[00:12:41.710]where they were just using one trait,
[00:12:44.110]and then they were starting to see resistance in those populations.
[00:12:48.040]So really important to use these multiple traits and
[00:12:52.870]then to always make sure that you are planning a refuge or using the refuge in
[00:12:57.850]the bag technology. Now, we also do have some biological control agents.
[00:13:02.770]So there are a variety of generalist predators, such as lady beetles,
[00:13:07.510]pirate bugs, these real small minute pirate, bugs, or Oreos,
[00:13:11.140]and then lacewings that are feeding on eggs and small larvae.
[00:13:16.000]Now they're, when these,
[00:13:19.150]when this past first was introduced in the United States,
[00:13:21.490]we had people from the USDA that went over to Europe,
[00:13:25.120]where these things originated and they were able to find some parasites.
[00:13:29.840]there are two parasitic wasps,
[00:13:32.050]and a parasitic fly that all three do help
[00:13:36.280]control the larvae, in the plants.
[00:13:38.980]And we do see these periodically out in our fields.
[00:13:42.340]we could also use some other biological controls. We,
[00:13:46.030]just like BT that's incorporated in the plant. We can actually make a, a,
[00:13:51.010]a foliar application or a granule application of BT products.
[00:13:55.930]And they'd do really a great job of controlling a European corn borer.
[00:14:00.370]There are also some naturally occurring pathogens, such as Bavaria, bossy Yana,
[00:14:04.900]or no SEMA pirate, PI Rosta that are,
[00:14:08.500]that will help control the larvae. And then finally,
[00:14:10.960]we do have some chemical controls and they all do work pretty well.
[00:14:14.530]There's a variety of liquid and granular insecticides labeled for European corn
[00:14:19.120]borer. We've kind of trended more toward the liquids and the granules, and,
[00:14:23.410]you'll have to make sure and look at the labels to make sure particularly
[00:14:26.320]first-generation is a, is labeled.
[00:14:28.840]There's just fewer products labeled for first-generation,
[00:14:31.480]but quite a few of them per second generation.
[00:14:34.360]And they're all labeled similarly for M B O corn,
[00:14:38.500]both yellow and white popcorn and sweet corn. And, you know,
[00:14:42.910]the control for reproductive stage tends to be a little more difficult.
[00:14:46.600]And so you need to try to time your application based on the egg hatch
[00:14:51.770]and, so that you get the chemical out on the,
[00:14:56.270]the plants, when the larvae are active and four,
[00:14:59.000]they get buried into the ear tip. And so following all those things,
[00:15:02.630]we can get some good control of European corn borer, and yes,
[00:15:06.020]they are still there. And,
[00:15:07.970]we just need to watch out for them and these crops that are non BT and can be
[00:15:12.790]susceptible. Thank you.

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4 - 2021 South Central Ag Lab Field Day - European Corn Borer

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