Mid and Late Season Insects

Michael Sindelar Author

10/01/2020 Added

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It’s a moth! It’s a beetle! No it’s the Nebraska Cropwatch Podcast! Mid and late season insects are the topic for this episode. So click on play and join Michael and Robert Wright for this ride.

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[00:00:00.036](gentle music playing)
[00:00:02.950]Welcome to "CropWatch Podcast",
[00:00:05.410]a production of Nebraska Extension.
[00:00:12.080]Welcome to the "CropWatch Podcast".
[00:00:13.900]I'm your host, extension educator Michael Sindelar.
[00:00:16.820]Today we're gonna be talking about insects.
[00:00:19.450]I'm gonna be joined today by Dr. Robert Wright
[00:00:22.330]who is a entomologist specialist
[00:00:26.510]here at the University of Nebraska.
[00:00:28.760]Good morning, Dr. Wright.
[00:00:29.650]How are you doing today?
[00:00:31.060]Good. How are you?
[00:00:32.370]Well, I'm doing great.
[00:00:33.785]Could a little bit more...
[00:00:34.618]Use a little bit more rain in the South Central
[00:00:36.340]part of the state but we could do without the wind.
[00:00:39.950]Right.
[00:00:40.783]So today, the first thing I would like to talk about
[00:00:44.290]is the university extension specialists such as yourself.
[00:00:49.390]They give us a lot of lovely,
[00:00:50.770]good data with their black light traps.
[00:00:53.710]How do we use that data
[00:00:55.210]and how are we supposed to interpret it?
[00:00:57.110]Okay. The short answer is our light trap network
[00:01:02.556]cannot be used to make treatment decisions
[00:01:05.540]in individual fields.
[00:01:07.500]We have four light traps
[00:01:08.970]at different locations across the state,
[00:01:11.100]at Northeast Nebraska, at Concord,
[00:01:13.340]at the Eastern Nebraska Research and Extension Center
[00:01:17.340]near Ithaca, at the South Central Ag Lab, near Clay Center,
[00:01:21.530]and the West Central Center at the North Platte.
[00:01:25.650]And black light traps,
[00:01:27.100]primarily your value in collecting
[00:01:30.050]or attracting night flying moths.
[00:01:32.830]So there's about a dozen different species
[00:01:35.090]that we keep track of that
[00:01:36.990]are potential pest problems on crops in Nebraska.
[00:01:40.740]And the main benefit is...
[00:01:43.110]One thing is knowing the timing
[00:01:44.810]of when different insects are occurring
[00:01:47.980]and something about the relative abundance.
[00:01:50.760]Like recently we've been seeing a fair number of
[00:01:53.150]yellow wooly bear moths
[00:01:55.150]at both Clay Center and North Platte.
[00:01:57.680]And I've seen...
[00:01:58.513]Seeing some reports
[00:01:59.720]that the people are seeing the caterpillars.
[00:02:02.340]Not necessarily economic levels yet
[00:02:04.940]but it gives us a little early warning
[00:02:07.430]of what we should be scouting for.
[00:02:10.050]Same thing with Western Bean Cutworm, we monitor that.
[00:02:13.390]We also have a degree-day model in that case.
[00:02:16.050]But it gives us a little bit of an update
[00:02:18.820]on where things are.
[00:02:20.340]The alternative for some insects is pheromone trapping.
[00:02:24.340]And pheromone trapping is probably more accurate
[00:02:27.170]but we have to have a different
[00:02:28.840]pheromone for each pest insect.
[00:02:31.350]And that gets to be rather expensive.
[00:02:33.640]The downside of the blacklight trap
[00:02:35.485]for individual farmers to use
[00:02:38.510]is that you have to be able to identify the 20
[00:02:42.890]or more different types of short through
[00:02:44.620]and identify the different moths that you're seeing.
[00:02:47.430]So if you're just interested in one insect,
[00:02:50.590]a pheromone trap might be the best approach.
[00:02:54.440]We're trying to get a general viewpoint
[00:02:56.540]of what's going on across the area.
[00:02:59.940]So the blacklight traps might be more of a...
[00:03:03.200]Like heads up for agronomists in an area
[00:03:05.740]to know what they might be looking for.
[00:03:08.930]Right, and for certain things, like I said,
[00:03:10.850]for Western Bean Cutworm,
[00:03:12.210]it helps us know when we should start scouting.
[00:03:15.370]For some insects,
[00:03:16.310]we have degree-day models,
[00:03:17.610]but for those that we don't,
[00:03:18.880]the blacklight trap tells us that
[00:03:21.910]the activity insects is varies with temperature.
[00:03:25.640]And so not so much the calendar date.
[00:03:28.400]And so the black light tells us what's going on.
[00:03:31.430]That with the timing of different particularly moth species
[00:03:35.690]this year in terms of their timing.
[00:03:38.840]And just to emphasize,
[00:03:41.980]it is not to be used to make management decisions.
[00:03:45.090]Right, because the moths will fly around
[00:03:48.310]and choose which fields are most attractive.
[00:03:52.690]For example, Western Bean Cutworm
[00:03:54.510]likes to lay eggs in pre-tassel corn if it has a choice.
[00:04:00.380]And so, in some years at the South Central Ag lab,
[00:04:03.810]we have very heavy moth flights
[00:04:06.290]but we don't necessarily get a lot of eggs in our fields
[00:04:09.570]depending on the phonology of the corn at the time
[00:04:12.940]the moths are flying.
[00:04:13.960]They will fly around and seek out the preferred plant states
[00:04:19.020]that they most like to lay eggs on.
[00:04:21.460]Well, it's been a hot, dry year,
[00:04:23.970]and not just in the South Central part of the state,
[00:04:26.830]but across the state.
[00:04:28.500]With that, are grasshoppers gonna be an issue
[00:04:31.030]as pastures and ditches dry out?
[00:04:34.140]Yeah, we are getting some reports.
[00:04:36.490]Obviously we didn't have a very heavy winter
[00:04:38.660]in terms of cold temperatures
[00:04:40.160]which can sometimes reduce overwintering survival
[00:04:43.820]of grasshopper eggs.
[00:04:46.060]And so we are...
[00:04:47.490]In some areas we have noticeable grasshopper,
[00:04:51.200]small grasshoppers in field boarders or pastures.
[00:04:55.500]And as you mentioned,
[00:04:56.910]in areas where the...
[00:04:58.180]We haven't got a lot of rain,
[00:05:00.350]that's gonna drive the grasshoppers into crops
[00:05:03.200]quicker than if we had more rain
[00:05:05.270]and the field borders and pastures were green and lush.
[00:05:09.590]The grasshoppers would stay there
[00:05:11.210]but areas where we are seeing the field borders
[00:05:15.460]or other areas dry up more quickly,
[00:05:18.950]they'll start moving into crops earlier
[00:05:21.010]and that is happening in some areas.
[00:05:22.930]So, certainly now is a good time to scout for grasshoppers
[00:05:27.130]and see if you have them on field borders or field edges.
[00:05:31.630]We have some rough guidelines
[00:05:33.280]in terms of the numbers that might be worth treating.
[00:05:37.450]In either situation we got a recent CropWatch article
[00:05:40.790]that describes this in more detail.
[00:05:43.380]Point is that if we do have reasonable numbers,
[00:05:47.720]it's better to control them before they get into the field.
[00:05:51.870]On the field borders you don't have to treat as much area
[00:05:54.720]and cost as much money in terms of insecticide,
[00:05:58.090]and also it's a lot easier
[00:05:59.710]to control small grasshoppers than larger ones.
[00:06:02.920]As they get bigger, they get harder to kill.
[00:06:05.570]So, if we have higher numbers
[00:06:08.150]it's easier to control them while they're small.
[00:06:11.880]That's a good point.
[00:06:12.750]It's easier to control them in the grass borders
[00:06:14.810]while they're small.
[00:06:15.920]Because you have less area.
[00:06:17.610]And they're more susceptible to the insecticide.
[00:06:21.860]So, what else are we seeing across the state for issues?
[00:06:25.240]Well probably in corn,
[00:06:28.270]two things that are happening right now,
[00:06:31.300]we have Western Bean Cutworms,
[00:06:33.290]have been laying eggs in some parts of the state
[00:06:35.640]for a couple of weeks
[00:06:36.610]and it's happening a little later further West in the state.
[00:06:40.290]But now is the time to be scouting
[00:06:42.350]for egg masses for Western Bean Cutworms.
[00:06:46.130]If we have high numbers,
[00:06:48.400]and it doesn't take that many,
[00:06:50.070]the threshold is between five to 8% of the plants
[00:06:53.870]with an egg mass or newly hatched larvae on the plant.
[00:06:57.270]If we do have that treatment level,
[00:06:59.370]we wanna wait until tassel emergence occurs to treat.
[00:07:03.760]And the new caterpillars as they hatch out,
[00:07:06.680]if they hatch out before tassel emergence,
[00:07:09.210]they'll feed on the developing tassel in the whorl,
[00:07:12.680]and then once the tassel emerges,
[00:07:15.470]they are more exposed feeding either still on the tassel
[00:07:19.160]or on the leaf axles.
[00:07:21.220]And we wanna have about a week probably
[00:07:24.380]between tassel emergence
[00:07:25.920]and when they start moving into the ear tip or ear.
[00:07:29.830]And if we do have high numbers,
[00:07:31.370]we wanna treat before they get into the ear.
[00:07:34.040]It's very hard to control them once they're inside the ear.
[00:07:36.640]So, regular scouting is important
[00:07:39.200]to check on the numbers and also if needed,
[00:07:42.720]the timing of insecticide application.
[00:07:46.180]So, where on the plant do we wanna
[00:07:47.630]look for those egg masses?
[00:07:49.710]Well, they're mostly on the upper part of the plant,
[00:07:52.040]upper third or half of the plant.
[00:07:54.970]And they're normally on the upper side of the leaf.
[00:07:57.790]Although some moths will lay it...
[00:08:00.090]Lay them anywhere but most of them
[00:08:02.450]are on the upper surface of the leaf
[00:08:05.370]and the upper third of the plant.
[00:08:07.440]And then as I said,
[00:08:08.350]once the eggs hatch they also...
[00:08:10.268]They find the caterpillars either in the emerged tassel
[00:08:15.420]or in the leaf axles feeding on pollen.
[00:08:18.340]Do we have any other headaches that are moving in
[00:08:21.370]or that we should be thinking about treating?
[00:08:24.763]Well the other thing is,
[00:08:26.180]again as we having soaking
[00:08:29.270]in a lot of parts of the state.
[00:08:32.320]Particularly rootworm beetles are a potential.
[00:08:36.230]They like to feed on green silks.
[00:08:39.990]And if there are high enough numbers
[00:08:41.650]particularly in high value crops,
[00:08:43.840]certainly seed corn or white corn or popcorn,
[00:08:48.176]and sweet corn too for that matter.
[00:08:51.730]We don't wanna interfere with pollination.
[00:08:54.230]If we have enough beetles that they're feeding,
[00:08:57.000]clipping the silks to within half of an inch of the husk,
[00:09:01.240]and they're doing that before the corn is pollinated,
[00:09:05.720]the seed is pollinated in the ear,
[00:09:08.520]that is a treatable level.
[00:09:10.430]And there are a few other insects,
[00:09:11.920]we have Japanese beetles in some areas
[00:09:14.150]that also like to feed on fresh silks.
[00:09:17.720]So watch for silk clipping insects as silks emerge.
[00:09:22.170]And again, if we have high populations
[00:09:24.770]that you wanna treat before they damage pollination.
[00:09:29.190]So I've seen in the South Central part
[00:09:30.880]some Japanese beetles moving in on soybeans.
[00:09:34.230]What are our thresholds
[00:09:36.020]for treating Japanese beetles on soybeans?
[00:09:39.290]Well, in general,
[00:09:40.270]we have quite a few different defoliating insects,
[00:09:43.330]leafing in insects on soybeans,
[00:09:45.210]grasshoppers, several caterpillars,
[00:09:47.957]and as you mentioned the Japanese beetle.
[00:09:50.740]And when we make a decision,
[00:09:52.260]we wanna try to evaluate defoliation from all insects
[00:09:56.490]and estimate defoliation levels across the whole canopy.
[00:10:00.150]And most of our soybeans are in reproductive stages now,
[00:10:04.020]and if we have 20% defoliation
[00:10:07.460]and insects are still feeding,
[00:10:10.170]that's a treatable level in reproductive stage soybeans.
[00:10:15.200]Is there anything else that we need
[00:10:16.100]to be on the lookout for?
[00:10:18.420]Oh, again, you mentioned earlier,
[00:10:20.330]it's been hot and dry in some areas,
[00:10:23.870]and we're getting some reports of spider mites on soybeans.
[00:10:28.130]And there probably are some in corn as well.
[00:10:30.610]We wanna watch out in both soybeans and corn,
[00:10:34.520]routine use of insecticide if we don't reach a threshold.
[00:10:38.300]In both soybeans and corn,
[00:10:40.410]that can set us up for later problems with spider mites
[00:10:44.129]because most of our insecticides for use
[00:10:47.130]are relatively broad spectrum
[00:10:49.080]and they kill off the natural enemies,
[00:10:51.030]the beneficial insects,
[00:10:52.820]the predatory insects that feed on immature
[00:10:56.210]and adult spider mites.
[00:10:57.810]And if we knock off the predators now,
[00:11:00.330]a small population of spider mites
[00:11:02.730]with the right environmental conditions
[00:11:04.720]can reproduce relatively rapidly.
[00:11:07.560]And so that's something to be watching for oftentimes.
[00:11:10.440]In corn or soybeans,
[00:11:12.500]it's the South or West facing part of the field
[00:11:16.040]that gets water stress.
[00:11:17.210]Maybe it's gonna develop
[00:11:18.980]or show spider mite populations first.
[00:11:21.790]So that's something to watch for.
[00:11:23.390]And then if you see yellowing of the leaves,
[00:11:25.710]yellow spots on the leaves
[00:11:27.630]and look on the undersides of the leaves
[00:11:29.370]and see small spider match,
[00:11:30.810]you need a hand lens probably to see them.
[00:11:33.380]That's something to check for as well.
[00:11:35.690]Is there anything we need to worry about with drought
[00:11:37.630]and how that affects how effective insecticides are?
[00:11:41.410]Oh, not so much drought
[00:11:43.090]but we know high temperatures,
[00:11:45.430]extremely high temperatures like in the above 95
[00:11:48.980]can reduce the efficacy
[00:11:50.730]and persistence of some insecticides.
[00:11:53.610]So that's something to be aware of.
[00:11:56.240]Do you have any upcoming programming Dr. Wright?
[00:11:59.770]Oh, I'm involved in several programs
[00:12:02.830]that are gonna be virtual.
[00:12:04.410]Several events in August,
[00:12:06.530]the soybean management field days
[00:12:09.380]and corn and soybean management field days
[00:12:13.000]that we normally have in August at different locations.
[00:12:16.930]They are all gonna be online this year.
[00:12:19.490]Well, thank you for joining us today, Dr. Wright.
[00:12:22.470]You're welcome.
[00:12:23.880]Hopefully we have a good growing season
[00:12:25.400]even though it's hot and dry.
[00:12:27.429](guitar strumming)

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Mid and Late Season Insects

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