Rice, Soybean, and Cotton Insect Update (6/15/21)

Today's podcast covers management strategies for rice water weevil and rice billbug in rice, stink bugs in soybean, as well as thrips and plant bugs in cotton. We cover thresholds and insecticide timings for these pests, as well as what to expect later in the year.

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Title: Rice, Soybean, and Cotton insect update, with Gus Lorenz, Ben Thrash and Nick Bateman (6/15/21)

Nick Bateman: Welcome to Arkansas Row Crops Radio. My name is Nick Bateman, extension entomologist for the University of Arkansas System Division of Agriculture. Today I’ve got Gus Lorenz and Ben Thrash with me. We’re going to hit on several things around a bunch of the crops around the state. One thing, a couple of weeks ago we did the podcast and we mentioned that we started seeing some rice water weevils finally starting to show up in rice and since then our phones have been blowing up. A lot of people are seeing a lot of scaring out there. One thing we need to keep in mind, if you’ve got Cruiser and NipsIt, odds are it’s gone by this point. Looking at all this rice around the state that hasn’t gone to flood that’s already knee high, we’re well past that thirty day window and we’re not expecting much activity out of that Cruiser or NipsIt at that point. You have Dermacor, your Fortenza, we would not spray that. Those products last much longer. They’re superior from a weevil standpoint, especially after that thirty day window compared to Cruiser or NipsIt. But if I’m in a historically bad place for rice water weevils and I’ve got Cruiser or NipsIt outside that thirty day window, I might consider a pre-flood there, something like lambda-cy . We see really good control with that but it doesn’t fit every acre. I’m not spraying every acre with a pre-flood insecticide. Just areas that I historically know that I have extremely high rice water weevil pressure.

Gus Lorenz: When we look at all our data over the past several years looking at pre-flood applications vs post-flood applications Nick, it’s pretty clear which is more efficacious for us and those pre-flood applications for whatever reason, if you’re in one of those areas where you now you’re going to have weevils, that’s not a bad way to go.

Nick: That data that Gus is mentioning is all coming from Pine Tree up there and you’ll have seen a bunch of our data from Pine Tree. On a mild year up there at Pine Tree we’re running thirty weevils in our untreated check per core. That’s ten times threshold, so I mean it’s notorious for high weevil pressure. So it makes sense in that area.

Gus: But I think most folks know that they have to respond to what happens after they get the flood on, and the calls that we’re getting, there’s a lot of weevils, adults in the field and half of them are mating at the time when people are seeing them. In that situation when you’ve forty to fifty percent scaring and a lot of adult activity in the field, I think you’ve got to pull the trigger on that.

Nick: Yep, there’s no doubt about it. And keep in mind Gus has mentioned adults being in the field, you go out there and see the scaring and no adults, you don’t have anything to spray for. You’ve got to target those adults and so that window’s usually in the first seven days after going to flood in most years. Another thing we’re starting to see show up in rice, at least row rice, is bill bug pressure. This is typically these first couple of weeks of June over the past four or five years, our monitoring has been the peak of activity that we see and we’re starting to see quite a bit of dead tillers showing up, that first sign of damage out there right before egg lay and keep in mind we’ve tried basically everything that’s out there from a foliar standpoint, both labeled, not labeled, different rates. We’re struggling to find something from a foliar standpoint. 

Gus: Chase indicates right now that the rice bill bugs are at a peak on coming into the fields right now and he’s seeing the weevils that are causing damage to the rice right now. So, it’s a good time to be out scouting for them. And it’s a good point, I mean so what do you do at this point if you’re seeing a bunch of bill bugs out there? If you didn’t use a diamide, like Fortenza or Dermacor, we haven’t been able to show any foliar applications doing much good have we?

Nick: No and I think the biggest thing you’re doing when you’re out there scouting right now is getting a feel for how much bill bug activity you have, to know how to make changes in the future. Like several of the fields we’ve been in up around that Oil Trough area, right outside Newport, that’s a hot spot for them. Even when we rotate fields and move a quarter or half a mile down the field, they seem to go find that row rice. So that’s a good thing to be out looking right now to know they’re in the area, because they will pick up and move and chase you for a quarter or  half mile pretty easily. 

Gus: So just because you’ve got some new fields that are row rice that doesn’t mean you’re going to be immune to problems. 

Nick: It doesn’t mean you’re safe.

Gus: We’re also seeing, we’ve been doing some work with the slugs Ben, why don’t you tell them what we found out with that.

Ben Thrash: Nick put out a study the other day on some slugs and using the Deadline where he banded some strips of that Deadline. And then he also put out some reduced rates of Deadline for the slugs and it seems like you don’t really want to cut that rate. You got to go with the ten pound Deadline rate. Everything lower than the ten pounds that we tested seemed to still get quite a bit of stand loss compared to that ten pound rate. 

Gus: It did look like if you banded that ten pound rate over the row that it did provide some control

Nick: There’s a general trend there that it was better than the other treatments. It may not have separated statistically but this is also our first shot at it too.

Ben: We’re going to keep doing some more work on that in the future, so 

Gus: But for now I mean if you’ve got slugs and you feel like you got to get them out, it looks like that ten pound rate is going to be the only rate. The five pound rate’s not good at all. 

Nick: So that slug, with it being a bait, what’s our window on rain there? How long would we like it to be in the field?

Gus: Twenty four to forty-eight hours is what I’d say. I think you’ve got to have it out there, you know it’s a bait and if it gets rained on it’s going to melt and it’s going to be gone and so the more time that it’s out there the better chance you’ve got of attracting those slugs to feed on it. But if you get a good rain it’s gone. You’ve put out a thirty dollar application and it’s gone. You can’t deal with that.  Growers can’t deal with that, so that’s not very . . . what else is going on?

Ben: Well just thinking about our moth traps. We were looking at our moth trap numbers the other day and they seemed to be down. They seemed to be a little off right now. There’s some hot spots around, you know we’ll have a trap or two that’ll catch a pretty decent number of moths. But over all the numbers are down. We stopped and looked at corn yesterday trying to find eggs on silks and we couldn’t find the first egg out there on the corn silk. Now I’m not telling you this to let your guard down. Don’t be out there not looking for worms. But a lot of people get really concerned that they’re missing worms out there in the field if they’re not finding any. But it just seems like there’s not a whole lot of moths out there. Not a lot of moth activity. Oh yeah, stink bugs in soybeans. A few people are finding some stinkbugs out in soybeans and with the weather that we’ve had, we’ve got quite a bit of uneven maturity in a lot of these fields and so a lot of times they can be spotty. They like to go to those most mature beans out there in the field because they’re seed feeders, so the ones that have the most amount of seed out there in the field is where you’re going to find those stinkbugs.  We’re getting into situations that we’ve got a lot of lower ends in fields that have been flooded and a lot of people are going to be out there doing some replanting and what they’re going to find is that if stink bugs come into the field they are going to be in the upper end of the field, they’re not going to be in the lower flooded half of the field or third of the field or whatever got replanted, they’ll only be up there in the top end of the field. And so these fields that have these varying maturities, you can’t manage the field on the whole field basis. You’re going to have to scout the upper end of the field. You’re going to have to scout the bottom end of the field because there’s a lot of different things that can happen. And especially when we get later on in the season, those earliest planted beans at the top end, they may miss the worms all together later on in the season. But the lower end of the field that got replanted it’s liable to be pretty covered up. 

Gus: We’ve got a crop of soybeans from still in the bag to, we got beans that are now at R2, R3, even R4 in some cases. You think about those fields that are R3 right now and R4, those stinkbugs are going, every stinkbug in the country is coming to those beans sooner or later and there are going to be very attractive to stinkbugs and you may see spikes in numbers right now. You need to really be scouting those fields that are already beginning to pod because they could be overwhelmed with stinkbug numbers right now. There’s just not a lot of stuff for those stinkbugs to go to and I think that’s their trap crop right now. I think they are just very attractive to a lot of pests.

Nick: So with these calls on stinkbugs, mine have been mainly greens with a few browns mixed in. Say it’s vice versa, say it’s mainly brown versus green. What’s your recommendations there when it comes to insecticides?

Gus: Yeah, our threshold is going to be around nine per twenty five, that’s going to be a pretty, and with the higher prices for beans right now we may pull the trigger just a little bit quicker than that. But our studies show that there’s a little leeway between that threshold of nine per twenty five and getting damage in the field. We did a lot of work with stinkbugs over the years and I’m going to let them get up to nine per twenty five. I’m going to let them get there before I treat. I’m not going to treat at four or five. I’m not going to do it. I think you’re wasting your money and I think that we need to adhere to those thresholds. We need to make as much as we can off of these beans that we got that are still alive that haven’t been flooded out and we got to do the best that we can and not being trigger happy and being patient and treat when you need to treat and not treat when you don’t. I think this is that situation where we can maximize the growers return on that kind of situation. So lastly we’ll talk a little bit about cotton. Obviously this has been the thrips year. We haven’t seen thrips like this in several years and the thrips damage out there is pretty severe in some cases and in our plots the untreated checks are just pretty much toast right now. They’re really taking it hard. The seed treatments held up okay, not great as we have seen in the past, the infurrow stuff is holding up a little better. A lot better actually in some cases. In our experience with the Thryvon technology has been extremely good this year. There’s been a lot of pressure on that technology this year with the thrips numbers but frankly I haven’t seen anything that I would have treated that was Thryvon at this point but I think some people saw it a little different but anyway now we’re getting into that special time between where you got some cotton that’s still susceptible to thrips about up to the fourth leaf stage. After that our studies show that treating after the fourth leaf you don’t get much out of that situation and particularly with the growing conditions we got right now the cotton is beginning to grow and move and we’ve got cotton that’s beginning to square pretty good and in some areas plant bug numbers are kind of high like we kind of thought they might be and thresholds on adults sweep counts anywhere from nine to twelve per hundred sweeps is threshold and we’re actually getting calls from a few people that have cotton at that ninth, tenth node and they’re beginning to see a little bit of the activity of adults moving in the field and with all the corn we got coming back and forth in those fields that are next to corn and that kind of thing, we need to be sweeping and looking for developing populations and watching that square retention is the biggest thing for me. I mean I’m eighty percent square retention and I start approaching if my square retention is starting to fall off a little bit down to around eighty percent it may be time to pull the trigger but our studies show that a little bit of plant bug activity out there is certainly not hurting yield and if they’re out there and they’re not at treatment level I wouldn’t get trigger happy. Every day we don’t spray is a good day for the grower and so if you can delay an application a couple of days or a few days and tag it up with a herbicide application or something like that, let’s just, let’s take care of the plant bugs but be cognoscent of what our thresholds are and use those thresholds and make good decisions right now. 

Nick: What else? 

Ben: I think that’s about all I got. 

Nick: Anything else on the cotton? 

Ben: I don’t think so 

Gus: We’re not seeing anything else. I don’t see much going on 

Ben: We’ve been looking at johnsongrass for sugarcane aphid and sorghum and we hadn’t really seen much around so, waiting on that one to blow up.

Gus: I guess that’s it. Thanks.

Nick: Appreciate it and thanks for joining us on Arkansas Row Crops Radio.


End notes: Arkansas Row Crops Radio is a production of the University of Arkansas System Division of Agriculture. For more information, please contact your local county extension agent or visit uaex.uada.edu.